This is a static version of the conservation advice for this site, generated on 20/09/2019.
Please check the latest advice for this site at https://designatedsites.naturalengland.org.uk/

Tamar Estuary Sites MCZ

Last updated: 20th March 2017

Supplementary advice

The Supplementary Advice on Conservation Objectives (SACOs) present attributes which are ecological characteristics or requirements of the designated species and habitats within a site. The listed attributes are considered to be those which best describe the site’s ecological integrity and which if safeguarded will enable achievement of the Conservation Objectives. These attributes have a target which is either quantified or qualified depending on the available evidence.

The target identifies as far as possible the desired state to be achieved for the attribute. In many cases, the attribute targets show if the current objective is to either ‘maintain’ or ‘recover’ the attribute.

Where there is no evidence to determine a marine feature’s condition, a vulnerability assessment, which includes sensitivity and exposure information for features and activities in a site, has been used as a proxy for condition. Evidence used in preparing the SACO has been cited with hyperlinks included where possible. Where references have not been provided, Natural England has applied ecological knowledge and expert judgement.

Some, but not all, of these attributes can also be used for regular monitoring of the condition of the designated features. The attributes selected for monitoring the features, and the standards used to assess their condition, are listed in separate monitoring documents, which will be available from Natural England. As condition assessment information becomes available, the conservation advice package will be reviewed accordingly.

When to use

You should use this information, along with the conservation objectives and case-specific advice issued by Natural England when developing, proposing or assessing an activity, plan or project that may affect the site.

Any proposals or operations which may affect the site or its features should be designed so they do not adversely affect any of the attributes in the SACO or achievement of the conservation objectives.

Feature target

‘Maintain’ targets do not preclude the need for management, now or in the future, to avoid a significant risk of damage or deterioration to the feature. The supporting and/or explanatory notes in the SACOs set out why the target was chosen and any relevant site based supporting information. This is based on the best available information, including that gathered during monitoring of the feature’s current condition.
Feature/Subfeature nameAttributeTargetSeasonSupporting notes
Intertidal coarse sedimentDistribution: presence and spatial distribution of biological communitiesMaintain the presence and spatial distribution of intertidal coarse sediment communitiesN/AA variety of communities make up the habitat. Listed component communities reflect the habitat's overall character and conservation interest. Communities are described as biotopes using EUNIS or the Marine Habitat Classification. Communities include, but are not limited to, those that are notable or representative of the feature. Representative communities include, for example, those covering large areas and notable communities include those that are rare, scarce or particularly sensitive to pressure. Changes to the spatial distribution of communities across the feature could highlight changes to the overall feature (Joint Nature Conservation Committee (JNCC), 2004).
Site-specifics:

The main community of this feature in the site is A2.111 'Barren littoral shingle.' A previous survey also recorded A2.222 'Oligochaetes in littoral mobile sand' with the sediment comprising coarse sand and gravel; however this was not recorded in the most recent survey (Curtis, 2010)(Bunker et al., 2002).


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

Intertidal coarse sedimentExtent and distributionMaintain the total extent and spatial distribution of intertidal coarse sediment.N/AThe extent describes the presence and area of the habitat. It’s the total area of the habitat across the site as a whole, even where it’s patchy. The distribution describes the more detailed location(s) and pattern of habitat across the site. The distribution will influence the component communities present, and also help increase the health and resilience of the feature (Joint Nature Conservation Committee (JNCC), 2004). A reduction in extent would alter the biological and physical functioning of the feature (Elliott et al., 1998). It's difficult to put an extent objective on a mobile, changing feature. An understanding of the supporting processes will be more helpful in determining site integrity. However, the extent can also be defined where the proportion of sediment-sensitive invertebrates (PSI) indicates a change to the sediment character. If there is insufficient evidence, the existing extent occurring at any one time should be the focus of an assessment due to the natural variation, and a fresh survey is likely to be required at the point of assessment, to ascertain what the existing extent is.
Site-specifics:

Existing information indicates an extent value of 1.3 ha for littoral coarse sediment (Curtis, 2010). The majority of this habitat within the site is located on the Tavy, in the Maristow Park and the Lopwell Quay area. A smaller area of this habitat is found on the Tamar south of Warren point. In the Tavy the habitat is patchy and surrounded by muddy sediments (Curtis, 2010).


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

Intertidal biogenic reefsExtent and distributionMaintain the total extent and spatial distribution of mussel beds.N/AThe extent describes the presence and area of the habitat. It’s the total area of the habitat across the site as a whole, even where it’s patchy. The distribution describes the more detailed location(s) and pattern of habitat across the site. The distribution will influence the component communities present, and also help increase the health and resilience of the feature. Although the overall extent will always vary, intertidal mussel beds can be relatively stable habitats with some areas persisting for several years in locations where suitable conditions occur. If there is insufficient evidence, the existing extent occurring at any one time should be the focus of an assessment due to the natural variation, and a fresh survey is likely to be required at the point of assessment, to ascertain what the existing extent is. The distribution of intertidal mussel beds will vary over time. Tracking the distribution will reveal the core beds. The aim for intertidal mussel beds is to understand where the core, persistent beds occur. However, areas of mussel beds outside core areas will also contribute to the existing distribution target (Joint Nature Conservation Committee (JNCC), 2004), (Fariñas-Franco et al., 2014).
Site-specifics:

Existing information indicates an extent value of 6.95 ha for Intertidal Biogenic Reef (Moore et al., 1999) (Curtis, 2010) (Cornwall Inshore Fisheries and Conservation Authority (CIFCA), 2015). In this site most beds are found crossing the boundary between the subtidal and intertidal zone.

The largest bed is found in the intertidal zone at Ernesettle on the Tamar. Part of the largely subtidal bed at Jupiter Point on the Lynher also falls into the intertidal area (Curtis, 2010) (Bunker et al., 2002). In 2014 an intertidal bed was identified at Shilligham Point opposite Jupiter Point and it is thought that these beds may actually connect sublittorally. There are also areas of mussel bed which fall outside the site boundary to the east of Jupiter point. The importance of these beds to the designated habitats is currently unknown.


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

Blue mussel (Mytilus edulis) bedsExtent and distributionMaintain the total extent and spatial distribution of mussel beds.N/AThe extent describes the presence and area of the habitat. It’s the total area of the habitat across the site as a whole, even where it’s patchy. The distribution describes the more detailed location(s) and pattern of habitat across the site. The distribution will influence the component communities present, and also help increase the health and resilience of the feature. Although the overall extent will always vary, intertidal mussel beds can be relatively stable habitats with some areas persisting for several years in locations where suitable conditions occur. If there is insufficient evidence, the existing extent occurring at any one time should be the focus of an assessment due to the natural variation, and a fresh survey is likely to be required at the point of assessment, to ascertain what the existing extent is. The distribution of intertidal mussel beds will vary over time. Tracking the distribution will reveal the core beds. The aim for intertidal mussel beds is to understand where the core, persistent beds occur. However, areas of mussel beds outside core areas will also contribute to the existing distribution target (Joint Nature Conservation Committee (JNCC), 2004), (Fariñas-Franco et al., 2014).
Site-specifics:

Existing information indicates an extent value of 6.95 ha for Intertidal Biogenic Reef (Moore et al., 1999) (Curtis, 2010) (Cornwall Inshore Fisheries and Conservation Authority (CIFCA), 2015). In this site most beds are found crossing the boundary between the subtidal and intertidal zone.

The largest bed is found in the intertidal zone at Ernesettle on the Tamar. Part of the largely subtidal bed at Jupiter Point on the Lynher also falls into the intertidal area (Curtis, 2010) (Bunker et al., 2002). In 2014 an intertidal bed was identified at Shilligham Point opposite Jupiter Point and it is thought that these beds may actually connect sublittorally. There are also areas of mussel bed which fall outside the site boundary to the east of Jupiter point. The importance of these beds to the designated habitats is currently unknown.


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

Blue mussel (Mytilus edulis) bedsExtent of subtidal biogenic reefWhen mussel beds develop within the site, their extent and persistence should not be compromised by human activities, accepting that, due to the naturally dynamic nature of this feature, their extent will change over time.N/AThe extent describes the presence and area of the habitat. It’s the total area of the habitat across the site as a whole, even where it’s patchy. The distribution describes the more detailed location(s) and pattern of habitat across the site. The distribution will influence the component communities present, and also help increase the health and resilience of the feature. The extent of mussel bed is an important attribute in relation to the health and survival of the biogenic reef, and where reef develops it contributes to the coherence of the feature. However, extent can be highly variable as mussel beds are ephemeral and difficult to detect. They can increase in area, reduce in area, change distribution, or simply disappear only to return following a recruitment event. Larger areas of reef, or areas of higher quality reef that persist over time, will be especially important for the conservation of the feature. The existing extent occurring at any one time should be the focus of an assessment due to the natural variation, and a fresh survey is likely to be required at the point of assessment, to ascertain what the existing extent is (Fariñas-Franco et al., 2014). (Holt et al., 1998)
Site-specifics:

Existing information indicates an extent value of 7.12 ha of blue mussel beds, which includes 6.95 ha of intertidal biogenic reef in addition to the subtidal beds (Moore et al., 1999) (Curtis, 2010) (Tyler, 2010) (Cornwall Inshore Fisheries and Conservation Authority (CIFCA), 2015). In this site most beds are found crossing the boundary between the subtidal and intertidal zone.

The main area of subtidal biogenic reef is the mussel bed just west of Jupiter point on the Lynher. On the Tamar a number of small subtidal beds have been recorded at Ernesettle, Saltmill Creek and Weir Point (Curtis, 2010) (Bunker et al., 2002). There are also areas of mussel bed which fall outside the site boundary to the east of Jupiter point, currently the importance of these beds to the designated habitats is not known.


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

Blue mussel (Mytilus edulis) bedsExtent of supporting habitatMaintain the area of habitat that is likely to support the feature, allowing for natural change and the dynamic nature of the habitat.N/AMussel reefs are completely reliant on the supporting habitat they colonise. The supporting habitat is likely to extend beyond the mussels themselves, however the mussels will only exist in certain areas. The beds are dynamic by nature and will move year on year. Areas where there is evidence for the ability of reef to persist over time, forming more elevated structures or consistently recolonising, will be particularly important for the conservation of the feature. Please note, some mussel beds are less / not ephemeral.
Site-specifics:

No site specific information.


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

Intertidal biogenic reefsExtent of supporting habitatMaintain the area of habitat which is likely to support the feature, allowing for natural change and the dynamic nature of the habitat.N/AMussel reefs are completely reliant on the supporting habitat they colonise. The supporting habitat is likely to extend beyond the mussels themselves, however the mussels will only exist in certain areas. The beds are dynamic by nature and will move year on year. Areas where there is evidence for the ability of reef to persist over time, forming more elevated structures or consistently recolonising, will be particularly important for the conservation of the feature. Please note, some mussel beds are less / not ephemeral.
Site-specifics:

No site specific information.


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

Native oyster (Ostrea edulis)Population: population sizeRecover the population size within the site.N/A

Population size is the number of individuals within a population that are able to contribute to the species viability at a local, national and bio-geographic scale. Population size relates to the abundance of a species. It should include all the populations of a species within the site. Abundance may vary spatially and temporally.

Native oysters prefer living where other oysters are found, and this influences where they settle during the larval stage (Kamphausen, 2012). The density of spawning native oysters should be sufficient enough to allow synchronous spawning or larval production for successful settlement (Haelters, 2009). Undisturbed areas, or ‘nuclei areas’ of sufficiently large oysters in a suitable density could allow oysters to provide larvae to the wider system, providing the population with much greater resilience (Laing et al., 2005), (Haelters, 2009).


Site-specifics:

Native oysters have undergone national population declines. Native oyster beds were considered scarce in Europe in the 1950s (Korringa, 1952) and the population is still regarded as depleted (Connor et al., 1997).


The recover objective for this species is based in part on nationwide population declines, with the native oyster population considered to be depleted.

Smelt (Osmerus eperlanus)Population: population sizeRecover the population size within the site.N/APopulation size is the number of individuals within a population that are able to contribute to the species viability at a local, national and bio-geographic scale. Population size relates to the abundance of a species. It should include all the populations of a species within the site. Abundance may vary spatially and temporally. Densities of smelt may be affected by changes to the physical, chemical or hydrological coherence of the site, and by potential exploitation in freshwater or marine and coastal waters. Such impacts may reduce the number of adults returning to spawn. As a short-lived species, smelt has relatively few year classes, therefore high catches repeated over a few years can lead to localised extinctions. During the summer recently hatched smelt are limited to certain parts of the estuary and restricted by salinity. This makes them very vulnerable to pollution events, which can wipe out a whole year class. Cooling water intakes can kill considerable numbers of European smelt (Maitland, 1997), (Maes et al., 2004).
Site-specifics:

It is considered that the weir at Gunnislake is acting as a barrier to smelt migration, potentially impacting on the population size by restricting access to suitable spawning habitat upstream. Smelt used to be a common species in England but populations have declined by 33% (Maitland and Lyle, 1996) (Joint Nature Conservation Committee (JNCC), 2010). There is a permanent population in the Tamar thought to have been established in 1968, however there is still a large amount of uncertainty regarding stocks of Smelt along the south coast of England (Nature, 2003).


The target has been set at 'recover' due to the potential impact of Gunnislake Weir on population size.

Smelt (Osmerus eperlanus)Population: recruitment and reproductive capabilityRecover the reproductive and recruitment capability of the species.N/ARecruitment and reproductive capability reflect the health and success of the population in terms of maintaining and / or restoring numbers. A reduction in the availability of individuals able to successfully reproduce, and survival rates, may impact the overall size and age-structure of the population. Smelt reach sexual maturity at different times depending on the origin of the population. Brackish populations become sexually mature at 3-4 years (15-18 cm), whereas freshwater populations become sexually mature at 1-2 years (8-10 cm). The thermal regime in the lower river during preceding weeks is considered the main factor in initiating spawning, but prevailing temperature, tide and flow conditions determine exactly where and when. Normally, spawning takes place during the highest spring tides when water has reached at least 5 °C. Smelt use stone, sand and gravel substratum, as well as soft vegetation, for spawning. Spawning usually takes place at night, and is communal with high proportions of the adult population present. Access to suitable habitat can be restricted by weirs, dams and other structures. Hatching occurs 3-4 weeks later. Juvenile abundance can be used as an indicator of breeding success. A large range in age structure and length may be an indicator of a healthy and productive population. This species can reach up to 45cm in length, but more typically they range between 10-20 cm. Sexual maturity develops at different sizes, depending on the location of the population (see recruitment / reproductive capability details). Males are usually smaller than females.
Site-specifics:

The only known spawning ground for smelt in the southwest is located within the Tamar section of the site (Tamar Estuaries Consultative Forum, 2012) (Defra, 2013). The spawning grounds within the Tamar are located just below Gunnislake Weir (Hillman, personal communication), with the weir restricting access further up the Tamar. There is also a second weir located downstream of Gunnislake Weir, however, this is passable on most high tides.


The target has been set at 'recover' as Gunnislake weir is likely to be acting as a barrier to migration, preventing the species from accessing the full extent of potential spawning grounds.

Native oyster (Ostrea edulis)Population: recruitment and reproductive capabilityRecover the reproductive and recruitment capability of the species.N/A

Recruitment and reproductive capability reflect the health and success of the population in terms of maintaining and / or restoring numbers. A reduction in the availability of individuals able to successfully reproduce, and survival rates, may impact the overall size and age-structure of the population.

Native oysters usually reach sexual maturity at about 3 years, or approximately 70 mm (Kamphausen, 2012). Generally, larger oysters produce more embryos (Cole, 1941). Successful reproduction and recruitment relies on the presence of large, mature adults whose distribution and abundance within a site should be close enough to allow for successful fertilisation. Optimal breeding is in June / July (Cole, 1941), with spawning mostly completed by late August (Kamphausen, 2012). Consideration should be given to the sex ratio in the event of a negative change to the age-size structure. Despite being hermaphrodites, oysters will normally display sex ratios of 1:1 male and female (Kamphausen, 2012).


Site-specifics:

No site specific information.


The recover objective for this species is based in part on nationwide population declines, with the native oyster population considered to be depleted.

Smelt (Osmerus eperlanus)Presence and spatial distribution of the speciesRecover the presence and spatial distribution of the species and their ability to undertake key life cycle stages and behaviours.N/AThe presence describes the mobile species occurrence, with the spatial distribution providing a more detailed overview of the location(s) and pattern of occurrence within a site. It is important to consider the key life stages and behaviours of a species as this may influence its distribution and ultimately population abundance. Disturbance caused by human activities should not adversely affect the species. Most populations are anadromous, spending the majority of the year in estuaries before spawning in or near the freshwater limit. Some populations are confined to freshwater lakes, although it’s thought that all of these populations in the UK are now extinct. Knowledge about the location of a population at various stages of the year is vital to understanding where to target management efforts. Smelt migrate towards breeding sites in large shoals during the spring. They are particularly vulnerable to human impacts during this stage of migration due to the confined nature of the population.
Site-specifics:

It is known that smelt in the Tamar migrate in large shoals to breeding sites during the spring (Dando, personal communication). The weir at Gunnislake confines the smelt to spawn just below the weir. There is also a second weir located downstream of Gunnislake Weir, however, this is passable on most high tides.


The target has been set at 'recover' as Gunnislake weir is likely to be acting as a barrier to migration, preventing the species from accessing the full extent of potential spawning grounds.

Native oyster (Ostrea edulis)Presence and spatial distribution of the speciesRecover the presence and spatial distribution of the species.N/A

The presence describes the species occurrence, with the spatial distribution providing a more detailed overview of the location(s) and pattern of occurrence within a site. It’s important to consider the various life stages of a species as this may influence its distribution. Disturbance caused by human activities should not adversely affect the species.

The presence and distribution of native oysters declined in the 20th century (Laing et al., 2005). Maintaining the geographical distribution of native oysters, and expanding distribution in its natural range, is a key conservation objective to improve chances of survival, as it helps to improve resilience (Haelters, 2009). Spatial distribution of native oysters within the site is also important for reproduction. If there's a large 'nearest neighbour distance' between individuals and / or beds this may affect recruitment by making fertilisation less likely (Kamphausen, 2012).


Site-specifics:

A survey of the mussel beds within the Lynher confirmed the presence of native oysters (Ostrea edulis). At Jupiter Point O.edulis were present in 70% of sample areas, but not in sufficient numbers to form a bed. Native oysters were also found on the Shillingham Point mussel bed, however, they were more common at Jupiter Point (Cornwall Inshore Fisheries and Conservation Authority (CIFCA), 2015).


The recover objective for this species is based in part on nationwide population declines, with the native oyster population considered to be depleted.

Smelt (Osmerus eperlanus)Structure and function: biological connectivityRecover biological connectivity between the estuary and the spawning and nursery grounds.N/AConnectivity is the extent to which populations in different parts of a species’ range are linked by the movement of eggs, larvae or other propagules, juveniles or adults (Palumbi, 2003). Smelt form large shoals in the lower reaches of estuaries and move up to spawn in the freshwater reaches in the early spring, usually just above the zone of saline influence. The spawning run tends to last only a few days, and disturbance during this period can have a significant negative impact on their fitness and survival. All migratory fish are very susceptible to obstacles during their spawning run. Physical structures such as weirs and dams are known to present permanent barriers to fish movements. Changes in water chemistry or flow speed can also cause temporary barriers to species movements, for example reduced dissolved oxygen concentrations are likely to create barriers to smelt migration (Maes et al., 2007). Man-made barriers and habitat fragmentation in coastal areas (ie tidal barrages) could also have a negative effect. Permanent or temporal gaps in the migratory corridors cause habitat fragmentation and impact heavily on local populations.
Site-specifics:

As the smelt ascend the Tamar estuary they are restricted by the weir at Gunnislake and therefore this species spawn just below the weir in brackish water. The post-larvae then drift downstream and feed between 5 and 10km downstream of the spawning zone, this feeding area is highly associated with the salt wedge (Journal of the Marine Biological Associataion (JMBA), 1975). There is also a second weir located downstream of Gunnislake Weir, however, this is passable on most high tides.


The target has been set at 'recover' as Gunnislake weir is likely to be acting as a barrier to migration, preventing the species from accessing the full extent of potential spawning grounds.

Blue mussel (Mytilus edulis) bedsStructure and function: presence and abundance of key structural and influential species[Maintain OR Recover OR Restore] the abundance of listed species, to enable each of them to be a viable component of the habitat.N/A

Natural England has included an attribute for the abundance of key structural and influential species for habitat features.

Structural species are those that form part of the habitat structure or help to define a key biotope.

Influential species are those that are likely to have a key role affecting the structure and function of the habitat (such as bioturbators (mixers of sediment), grazers, surface borers, predators or other species with a significant functional role linked to the habitat).

These will be identified at a national level in accordance with the criteria defined in the key structural and influential species paper (Covey et al., 2016). *For each species listed the reason for its inclusion as structural or influential and the information supporting its presence within the community of this site will be provided.


Site-specifics:


Blue mussel (Mytilus edulis) bedsStructure and function: presence and abundance of key structural and influential species[Maintain OR Recover OR Restore] the abundance of listed species, to enable each of them to be a viable component of the habitat.N/A

Natural England has included an attribute for the abundance of key structural and influential species for habitat features.

Structural species are those that form part of the habitat structure or help to define a key biotope.

Influential species are those that are likely to have a key role affecting the structure and function of the habitat (such as bioturbators (mixers of sediment), grazers, surface borers, predators or other species with a significant functional role linked to the habitat).

These will be identified at a national level in accordance with the criteria defined in the key structural and influential species paper (Covey et al., 2016). *For each species listed the reason for its inclusion as structural or influential and the information supporting its presence within the community of this site will be provided.


Site-specifics:


Intertidal coarse sedimentStructure and function: presence and abundance of key structural and influential species[Maintain OR Recover OR Restore] the abundance of listed species, to enable each of them to be a viable component of the habitat.N/A

Natural England has included an attribute for the abundance of key structural and influential species for habitat features.

Structural species are those that form part of the habitat structure or help to define a key biotope.

Influential species are those that are likely to have a key role affecting the structure and function of the habitat (such as bioturbators (mixers of sediment), grazers, surface borers, predators or other species with a significant functional role linked to the habitat).

These will be identified at a national level in accordance with the criteria defined in the key structural and influential species paper (Covey et al., 2016). *For each species listed the reason for its inclusion as structural or influential and the information supporting its presence within the community of this site will be provided.


Site-specifics:


Intertidal biogenic reefsStructure and function: presence and abundance of key structural and influential species[Maintain OR Recover OR Restore] the abundance of listed species, to enable each of them to be a viable component of the habitat.N/A

Natural England has included an attribute for the abundance of key structural and influential species for habitat features.

Structural species are those that form part of the habitat structure or help to define a key biotope.

Influential species are those that are likely to have a key role affecting the structure and function of the habitat (such as bioturbators (mixers of sediment), grazers, surface borers, predators or other species with a significant functional role linked to the habitat).

These will be identified at a national level in accordance with the criteria defined in the key structural and influential species paper (Covey et al., 2016). *For each species listed the reason for its inclusion as structural or influential and the information supporting its presence within the community of this site will be provided.


Site-specifics:


Intertidal biogenic reefsStructure: age / size frequencyMaintain a balanced age / size frequency and distribution within the population across the extent of the feature, to increase resilience and encourage a healthy productive population.N/AThe full range of ages and sizes of the species should be present within the site to ensure a healthy, productive population. The population’s age-size frequency should not change as a result of human activity, ie the loss of adults at sexual maturity, or young juveniles. Age and size can differ slightly for biogenic reefs but both are important to maintain a healthy, resilient population. Reefs with a range of ages / sizes also provide more heterogeneous habitats, creating a variety of ecological niches and diverse associated communities. Size is important because larger mussels put more energy into reproduction. Age is important because older mussels tend to be larger, although this does not always apply. Reproduction is important for the long-term viability of the mussel beds. The mussels' ability to reproduce is affected by their health. A balanced age / size frequency would contain the range of ages and sizes needed for a healthy population (Fariñas-Franco et al., 2014).
Site-specifics:

The average mussel length recorded on the Jupiter Point mussel bed was 65.3mm. The mussels at Shillingham Point were slightly smaller with an average of 60.7mm. The Jupiter Point mussels sampled varied from 34mm to 77mm, while the Shillingham Point mussels sampled ranged from 29mm to 78mm. The majority of the mussels on the Shillingham Point and Jupiter Point beds are adult mussels, with very little spat or juvenile mussel present (Cornwall Inshore Fisheries and Conservation Authority (CIFCA), 2015). No data is available for the other beds.


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

Blue mussel (Mytilus edulis) bedsStructure: age / size frequencyMaintain a balanced age / size frequency and distribution within the population across the extent of the feature, to increase resilience and encourage a healthy productive population.N/AThe full range of ages and sizes of the species should be present within the site to ensure a healthy, productive population. The population’s age-size frequency should not change as a result of human activity, ie the loss of adults at sexual maturity, or young juveniles. Age and size can differ slightly for biogenic reefs but both are important to maintain a healthy, resilient population. Reefs with a range of ages / sizes also provide more heterogeneous habitats, creating a variety of ecological niches and diverse associated communities. Size is important because larger mussels put more energy into reproduction. Age is important because older mussels tend to be larger, although this does not always apply. Reproduction is important for the long-term viability of the mussel beds. The mussels' ability to reproduce is affected by their health. A balanced age / size frequency would contain the range of ages and sizes needed for a healthy population (Fariñas-Franco et al., 2014).
Site-specifics:

The average mussel length recorded on the Jupiter Point mussel bed was 65.3mm. The mussels at Shillingham Point were slightly smaller with an average of 60.7mm. The Jupiter Point mussels sampled varied from 34mm to 77mm, while the Shillingham Point mussels sampled ranged from 29mm to 78mm. The majority of the mussels on the Shillingham Point and Jupiter Point beds are adult mussels, with very little spat or juvenile mussel present (Cornwall Inshore Fisheries and Conservation Authority (CIFCA), 2015). No data is available for the other beds.


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

Blue mussel (Mytilus edulis) bedsStructure: age / size frequencyMaintain a balanced age / size frequency and distribution within the population across the extent of the feature, to increase resilience and encourage a healthy productive population.N/AThe full range of ages and sizes of the species should be present within the site to ensure a healthy, productive population. The population’s age-size frequency should not change as a result of human activity, ie the loss of adults at sexual maturity, or young juveniles. Age and size can differ slightly for biogenic reefs but both are important to maintain a healthy, resilient population. Reefs with a range of ages / sizes also provide more heterogeneous habitats, creating a variety of ecological niches and diverse associated communities. Size is important because larger mussels put more energy into reproduction. Age is important because older mussels tend to be larger, although this does not always apply. Reproduction is important for the long-term viability of the mussel beds. The mussels' ability to reproduce is affected by their health. A balanced age / size frequency would contain the range of ages and sizes needed for a healthy population (Fariñas-Franco et al., 2014).
Site-specifics:

The average mussel length recorded on the Jupiter Point intertidal bed was 65.3mm, and the mussels at Shillingham Point intertidal bed were slightly smaller with an average of 60.7mm. The Jupiter Point mussels sampled varied from 34mm to 77mm, while the Shillingham Point mussels sampled ranged from 29mm to 78mm. The majority of the mussels on the Shillingham Point and Jupiter Point beds are adult mussels, with very little spat and juvenile mussel present (Cornwall Inshore Fisheries and Conservation Authority (CIFCA), 2015). No data is available for the other beds. (Fariñas-Franco et al., 2014)


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

Blue mussel (Mytilus edulis) bedsStructure: non-native species and pathogensReduce the introduction and spread of non-native species and pathogens, and their impacts.N/ANon-native species may become invasive and displace native organisms by preying on them or out-competing them for resources such as food, space or both. In some cases this has led to the loss of indigenous species from certain areas (Joint Nature Conservation Committee (JNCC), 2004). A pathogen causes disease or illness to its host. Pathogens include bacteria, viruses, protozoa and fungi (Biology-Online, 2008).
Site-specifics:

Pacific oysters (Crassostrea gigas) are present on mussel beds within the site, they are large individuals and are very sparsely populated. No juveniles were observed on beds at Jupiter Point and Shillingham (Cornwall Inshore Fisheries and Conservation Authority (CIFCA), 2015). A number of other non-natives have been recorded within mussel beds at the site.

Five different pathogens, including the paramyxian (Marteilia sp.) have been recorded from mussels growing on rock within the wider Tamar estuary. Prevalence of the pathogens was increased in the upper estuary, possibly as a stress response to increases in pollutants. Marteilia was found in up to 31% of individuals, which is the highest prevalence recorded in UK waters. This pathogen causes inflammation of digestive tissues and reduced reproductive output (Bignell et al., 2011). It is not known if these pathogens are present within the blue mussel beds.


Pacific oysters are present on mussel beds within this site; therefore a target of 'reduce' has been set for this attribute.

Intertidal biogenic reefsStructure: non-native species and pathogensReduce the introduction and spread of non-native species and pathogens, and their impacts.N/ANon-native species may become invasive and displace native organisms by preying on them or out-competing them for resources such as food, space or both. In some cases this has led to the loss of indigenous species from certain areas (Joint Nature Conservation Committee (JNCC), 2004). A pathogen causes disease or illness to its host. Pathogens include bacteria, viruses, protozoa and fungi (Biology-Online, 2008).
Site-specifics:

Pacific oysters (Crassostrea gigas) are present on mussel beds within the site, they are large individuals and are very sparsely populated. No juveniles were observed on beds at Jupiter Point and Shilligham (Cornwall Inshore Fisheries and Conservation Authority (CIFCA), 2015). A number of other non-natives have been recorded within mussel beds at the site.

Five different pathogens, including the paramyxian (Marteilia sp.) have been recorded from mussels growing on rock within the wider Tamar estuary. Prevalence of the pathogens was increased in the upper estuary, possibly as a stress response to increases in pollutants. Marteilia was found in up to 31% of individuals, which is the highest prevalence recorded in UK waters. This pathogen causes inflammation of digestive tissues and reduced reproductive output (Bignell et al., 2011). It is not known if these pathogens are present within the blue mussel beds.


Pacific oysters are present on mussel beds within this site; therefore a target of 'reduce' has been set for this attribute.

Native oyster (Ostrea edulis)Structure: Non-native species and pathogensReduce the introduction and spread of non-native species and pathogens, and their impacts.N/A

Non-native species may become invasive and displace native organisms by preying on them or out-competing them for resources such as food, space or both. In some cases this has led to the loss of indigenous species from certain areas (Joint Nature Conservation Committee (JNCC), 2004). A pathogen causes disease or illness to its host. Pathogens include bacteria, viruses, protozoa and fungi (Biology-Online, 2008). The physiological health of native oysters is important for ensuring a productive and resilient population. Bonamia ostreae is a parasite that can infect and cause mortality in native oysters (Kamphausen, 2012).


Site-specifics:

Native oysters are frequently found on mussel beds in the MCZ. Non-native Pacific oysters (Crassostrea gigas) and slipper limpets (Crepidula fornicata) are both present on mussel beds within the site (Cornwall Inshore Fisheries and Conservation Authority (CIFCA), 2015). The American oyster drill shellfish (Urosalpinx cinerea) has not yet been recorded in the site, but has recently been recorded in Plymouth Sound (network, 2015).

The native oyster is vulnerable to lethal infection from the disease Bonamiosis, which spreads via the parasitic protozoan Bonamia ostreae. B.ostreae has been recorded from oysters within Plymouth Harbour (Howard, 1994), but its presence and impact within the site are unknown.


Pacific oysters, slipper limpets and other non-natives are present on mussel beds and within the wider site; therefore a target of 'reduce' has been set for this attribute.

Blue mussel (Mytilus edulis) bedsStructure: non-native species and pathogensReduce the introduction and spread of non-native species and pathogens, and their impacts.N/ANon-native species may become invasive and displace native organisms by preying on them or out-competing them for resources such as food, space or both. In some cases this has led to the loss of indigenous species from certain areas (Joint Nature Conservation Committee (JNCC), 2004). A pathogen causes disease or illness to its host. Pathogens include bacteria, viruses, protozoa and fungi (Biology-Online, 2008).
Site-specifics:

Pacific oysters (Crassostrea gigas) are present on mussel beds within the site, they are large individuals and are very sparsely populated. No juveniles were observed on beds at Jupiter Point and Shilligham (Cornwall Inshore Fisheries and Conservation Authority (CIFCA), 2015). A number of other non-natives have been recorded within mussel beds at the site.

Five different pathogens, including the paramyxian (Marteilia sp.) have been recorded from mussels growing on rock within the wider Tamar estuary, prevalence of the pathogens was increased in the upper estuary, possibly as a stress response to increases in pollutants. Marteilia was found in up to 31% of individuals, which is the highest prevalence recorded in UK waters. This pathogen causes inflammation of digestive tissues and reduced reproductive output (Bignell et al., 2011). It is not known if these pathogens are present within the blue mussel beds.


Pacific oysters are present on mussel beds within this site; therefore a target of 'reduce' has been set for this attribute.

Intertidal coarse sedimentStructure: non-native species and pathogensRestrict the introduction and spread of non-native species and pathogens, and their impacts.N/ANon-native species may become invasive and displace native organisms by preying on them or out-competing them for resources such as food, space or both. In some cases this has led to the loss of indigenous species from certain areas (Joint Nature Conservation Committee (JNCC), 2004). A pathogen causes disease or illness to its host. Pathogens include bacteria, viruses, protozoa and fungi (Biology-Online, 2008).
Site-specifics:

Non-native species have been recorded from within or in close proximity to the site. Species include the Pacific oyster (Crassostrea gigas), the American slipper limpet (Crepidula fornicata), and the alga (Gracilaria multipartita) (Lush et al., 2015).


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

Smelt (Osmerus eperlanus)Structure: Non-native species and pathogensRestrict the introduction and spread of non-native species and pathogens, and their impacts.N/ANon-native species may become invasive and displace native organisms by preying on them or out-competing them for resources such as food, space or both. In some cases this has led to the loss of indigenous species from certain areas (Joint Nature Conservation Committee (JNCC), 2004). A pathogen causes disease or illness to its host. Pathogens include bacteria, viruses, protozoa and fungi (Biology-Online, 2008). Individuals infected with parasites in experimental conditions were found to have reduced swimming speeds, potentially impacting their ability to avoid predators and human disturbance. Smelt with more than 3 nematodes where shown to be significantly affected. Parasite loads ranging between 20-40% have been recorded (Sprengel and Luchtenberg, 1991).
Site-specifics:

Although the GMA for the feature is recover, there is no evidence that this attribute is in need of recovery. The target has therefore been set at 'restrict.’

Non-native species recorded from within or in close proximity to the site include; Pacific oysters (Crassostrea gigas), American slipper limpets (Crepidula fornicata) and the alga (Gracilaria multipartita) (Lush et al., 2015).


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

Intertidal biogenic reefsStructure: population densityMaintain the density of mussels.N/ADensity is the number of mussels per square metre. Density is an important component of the composition of intertidal mussel beds as it's an indicator of reef health. A low density of mussels may be the result of excessive physical or biological pressures. The composition of the biogenic reefs, together with the distribution is critical for the overall abundance (total volume). However, mussel beds can be ephemeral and the density will vary spatially and temporally (Fariñas-Franco et al., 2014).
Site-specifics:

In 2014/15 the Cornwall Inshore Fisheries and Conservation Authority undertook a stock assessment of intertidal blue mussel beds at Jupiter Point and Shillingham Point. This only covers the fishable areas of the bed, so may not be representative of other areas. Mussel cover was found to be 47% at Shillingham Point, compared with 34% on the Jupiter Point bed (Cornwall Inshore Fisheries and Conservation Authority (CIFCA), 2015).


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

Blue mussel (Mytilus edulis) bedsStructure: population densityMaintain the density of mussels.N/ADensity is the number of mussels per square metre. Density is an important component of the composition of intertidal mussel beds as it's an indicator of reef health. A low density of mussels may be the result of excessive physical or biological pressures. The composition of the biogenic reefs, together with the distribution is critical for the overall abundance (total volume). However, mussel beds can be ephemeral and the density will vary spatially and temporally (Fariñas-Franco et al., 2014).
Site-specifics:

In 2014/15 the Cornwall Inshore Fisheries and Conservation Authority undertook a stock assessment of intertidal blue mussel beds at Jupiter Point and Shillingham Point. This only covers the fishable areas of the bed, so may not be representative of other areas. Mussel cover was found to be 47% at Shillingham Point, compared with 34% on the Jupiter Point bed (Cornwall Inshore Fisheries and Conservation Authority (CIFCA), 2015).


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

Blue mussel (Mytilus edulis) bedsStructure: population densityMaintain the density of mussels.N/ADensity is the number of mussels per square metre. Density is an important component of the composition of subtidal mussel beds as it's an indicator of reef health. A low density of mussels may be the result of excessive physical or biological pressures. The composition of the biogenic reefs, together with the distribution, is critical for the overall abundance (total volume). However, mussel beds can be ephemeral and the density will vary spatially and temporally (Fariñas-Franco et al., 2014).
Site-specifics:

In 2014/15 the Cornwall Inshore Fisheries and Conservation Authority undertook a stock assessment of intertidal blue mussel beds at Jupiter Point and Shillingham Point. This only covers the fishable areas of the bed so may not be representative of other areas. Mussel cover was found to be 47% at Shillingham, compared with 34% on the Jupiter Point bed (Cornwall Inshore Fisheries and Conservation Authority (CIFCA), 2015).


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

Intertidal coarse sedimentStructure: sediment composition and distributionMaintain the distribution of sediment composition types across the feature.N/ASediment character is important in determining the biological communities present. Varied sediment type and grain size ensure structural complexity and connectivity. Intertidal sediments (ranging from highly stable mudflats and saltmarshes, to highly mobile shingle and sand beaches) are subject to a range of deposition and erosion processes, which human activity can influence. Most intertidal sediments stabilise over time so maintaining the sediment composition supports natural succession of the habitats and communities. Where they are subject to constant (net) erosion, the natural processes will be adversely affected (Gray and Elliott, 2009).
Site-specifics:

No site specific information.


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

Intertidal coarse sedimentStructure: sediment total organic carbon contentMaintain total organic carbon (TOC) content in the sediment at existing levels.N/ATotal Organic Carbon (TOC) content can be used for measuring change in the organic input to the mudflat / sandflat. TOC content of the sediment can influence community structure and contaminant levels (Viaroli et al., 2004).
Site-specifics:

No site specific information.


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

Intertidal coarse sedimentStructure: species composition of component communitiesMaintain the species composition of component communitiesN/A

Species composition of communities includes a consideration of both the overall range of species present within the community, as well as their relative abundance. Species considered need not be restricted to sessile benthic species but could include mobile species associated with the benthos. Species composition could be altered by human activities without changing the overall community type. Within each component community, species composition and population structure should be taken into consideration to avoid diminishing biodiversity and affecting ecosystem functioning within the habitat (Joint Nature Conservation Committee (JNCC), 2004).

The sediment community composition will change when the habitat is subjected to pollutants and other forms of disturbance, but will also be subject to significant natural variation annually. Benthic invertebrate communities are a good indicator of the health of the feature, if assessed over time (Joint Nature Conservation Committee (JNCC), 2004).


Site-specifics:

No site specific information.


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

Intertidal biogenic reefsStructure: species composition of the communityMaintain the species composition of the mussel bed community.N/A

Species composition of communities includes a consideration of both the overall range of species present within the community, as well as their relative abundance. Species considered need not be restricted to sessile benthic species but could include mobile species associated with the benthos. Species composition could be altered by human activities without changing the overall community type. Within each component community, species composition and population structure should be taken into consideration to avoid diminishing biodiversity and affecting ecosystem functioning within the habitat (Joint Nature Conservation Committee (JNCC), 2004).

(Fariñas-Franco et al., 2014)


Site-specifics:

No site specific information.


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

Blue mussel (Mytilus edulis) bedsStructure: species composition of the communityMaintain the species composition of the mussel bed community.N/A

Species composition of communities includes a consideration of both the overall range of species present within the community, as well as their relative abundance. Species considered need not be restricted to sessile benthic species but could include mobile species associated with the benthos. Species composition could be altered by human activities without changing the overall community type. Within each component community, species composition and population structure should be taken into consideration to avoid diminishing biodiversity and affecting ecosystem functioning within the habitat (Joint Nature Conservation Committee (JNCC), 2004).

(Fariñas-Franco et al., 2014)


Site-specifics:

No site specific information.


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

Blue mussel (Mytilus edulis) bedsStructure: species composition of the communityMaintain the species composition of the mussel bed community.N/A

Species composition of communities includes a consideration of both the overall range of species present within the community, as well as their relative abundance. Species considered need not be restricted to sessile benthic species but could include mobile species associated with the benthos. Species composition could be altered by human activities without changing the overall community type. Within each component community, species composition and population structure should be taken into consideration to avoid diminishing biodiversity and affecting ecosystem functioning within the habitat (Joint Nature Conservation Committee (JNCC), 2004).

(Fariñas-Franco et al., 2014)


Site-specifics:

No site specific information.


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

Intertidal coarse sedimentStructure: topographyMaintain the presence of topographic features, while allowing for natural responses to hydrodynamic regime, by preventing erosion or deposition through human-induced activity.N/ATopography is considered an essential structural component for this feature. Alterations in topography can cause changes in the slope angle of the foreshore or result in increases or decreases in surface elevation. Topographic changes can alter the way the sediment drains and holds water, and can also alter the tidal exposure, meaning areas can be covered by the tide for longer or shorter periods. This can influence the animal and plant communities supported (Gray and Elliott, 2009) and reduce the areas available to coastal birds for feeding. Such changes could occur through direct interaction, such as sand extraction, or indirect impacts, such as changes in wave height or tidal flow regime, which cause erosion or deposition (Elliott et al., 1998).
Site-specifics:

The estuaries within this site are rias, they are relatively deep and narrow compared to other estuaries, which have more steeply sloping banks. The banks have been modified in places, such as the naval dockyard at Devonport. Further up the estuaries the topography is largely natural and unaltered. Geomatics Surveys using LiDAR conducted by the Environment Agency in 2007 and 2011 indicated no significant change (±0.15 m) in elevation between these two time periods for nearly all of the Plymouth Sound and estuaries areas, with the exception of a very few small, isolated incidences of riverbank erosion in the upper reaches of the Tamar Estuary (Geomatics, 2013).


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

Smelt (Osmerus eperlanus)Supporting habitat: extent and distributionMaintain the extent and spatial distribution of the following supporting habitats: estuaries, saltmarsh, subtidal mixed sediments and subtidal coarse sediments.N/AThe extent of supporting habitats captures the presence and area of the habitats that the species relies on. The distribution of supporting habitat will partially govern the distribution of the species, and maintaining or recovering the distribution of supporting habitats will help ensure the stability of this species. Supporting habitats may not be limited to those described in the target. Smelt primarily live in estuaries and may use the whole estuary system, from the open coast to the tidal limits. They may also need clean areas of subtidal mixed or coarse sediments for spawning (Maitland, 2003). Access to suitable habitats for spawning is needed to maintain a viable population. Human activities should not be allowed to impact the spawning distribution of populations within the estuary, or restrict their distribution within the site. Noise disturbance within the estuary (eg construction work and shipping) could be a disturbing factor to smelt, excluding them from suitable supporting habitat. It may interfere with feeding behaviours, predator avoidance and migration to and from spawning grounds.
Site-specifics:

Although the GMA for this feature is recover, NE's expert advice is that this attribute has not been impacted. The target has therefore been set at 'maintain.'


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

Native oyster (Ostrea edulis)Supporting habitat: extent and distributionMaintain the extent and spatial distribution of the following supporting habitats: mussel beds, intertidal rock, intertidal sediment, subtidal rock and subtidal sediment.N/A

The extent of supporting habitats captures the presence and area of the habitats that the species relies on. The distribution of supporting habitat will partially govern the distribution of the species, and maintaining or recovering the distribution of supporting habitats will help ensure the stability of this species. Supporting habitats may not be limited to those described in the target. There is evidence that native oyster spat (young oysters) have a preference for settling on the shells of dead or living oysters (Haelters, 2009) and / or other molluscan shells (Woolmer et al., 2011). They can also be found on a variety of stable substrates, including bedrock, boulders, pebbles, gravels, shell, muddy gravels, muddy sand, mud and artificial surfaces.


Site-specifics:

Although the GMA for this feature is recover, NE's expert advice is that this attribute has not been impacted. The target has therefore been set at 'maintain.’

Native oysters within this site were frequently found growing on mussel beds (Tyler, 2010).


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

Smelt (Osmerus eperlanus)Supporting habitat: food availabilityMaintain the cover / abundance of preferred food items required by the species.N/AThe availability of an abundant food supply is critically important for successful breeding, adult fitness and survival, and the overall sustainability of the population. Inappropriate management and direct or indirect impacts that affect the distribution, abundance and availability of food items may adversely affect the population. Smelt feed primarily on small crustaceans and small fish such as sprat, herring and gobies. Juvenile Smelt feed on small planktonic crustaceans such as the copepod Eurytemora affini, Gammarus species and mysid shrimp.
Site-specifics:

Although the GMA for this feature is recover, NE's expert advice is that this attribute has not been impacted. The target has therefore been set at 'maintain.'


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

Blue mussel (Mytilus edulis) bedsSupporting processes: areas with conditions suitable for reef formationMaintain the environmental conditions in those locations that are known, or which become known, to be important for mussel bed formation.N/AMussel beds are reliant on the physical and biological process that allow reef to form, these include: favourable ground conditions, temperature, a supply of spat, supply of sediment, supply of food, and the water movements conveying these to the bed (see also attributes for physico-chemical properties and water movement). This attribute serves to highlight the importance of wider processes for the distribution of beds within the site, and their ability to form. Areas where there is evidence for the ability of reef to persist over time, forming more elevated structures or consistently recolonising, will be especially important for the conservation of the feature.
Site-specifics:

No site specific information.


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

Intertidal coarse sedimentSupporting processes: energy / exposureMaintain the natural physical energy resulting from waves, tides and other water flows, so that the exposure does not cause alteration to the biotopes and stability, across the habitat.N/AThe amount of energy received across the site significantly affects the communities present. Physical energy can be received through wave energy and / or tidal flow, and can be altered through human activity. Any such alterations to energy should be avoided (Hiscock et al., 2006). Ambient energy levels related to wave and tidal action influence the amount of physical disturbance experienced by seabed sediments. Physically stable or immobile sediments often support different animal and plant communities when compared with mobile or disturbed sediments (Gray and Elliott, 2009). Therefore, understanding the site's baseline conditions is very importance. However, due to the complexity of measuring the energy and disturbance levels of an area, it's unlikely that a quantifiable objective could be determined.
Site-specifics:

Peak tidal current speed within the Tamar reaches a maximum 20 km upstream of the Narrows. Timing of peak flood current velocity is progressively later with distance towards the head of the estuary. Flood currents are significantly greater than ebb currents, with the duration of the ebb longer than that of the flood (Debut, 2007).


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

Intertidal coarse sedimentSupporting processes: physico-chemical propertiesMaintain the natural physico-chemical properties of the water.N/AThe physico-chemical properties that influence habitats include salinity, pH and temperature. They can act alone or in combination to affect habitats and their communities in different ways, depending on species-specific tolerances. In coastal habitats they can vary widely and can influence the abundance, distribution and composition of communities at relatively local scales. Changes in any of these properties, as a result of human activities, may impact habitats and the communities they support (Elliott et al., 1998), (Gray and Elliott, 2009), (Little, 2000).
Site-specifics:

Salinity is variable within the site although it very rarely reaches full salinity. Between Devil’s Point and the Tamar Bridge on the Tamar Estuary salinity is typically between 20 and 30 ppt. In the upper estuary between Cargreen and South Hooe salinity is typically in the region of 5ppt and in the riverine estuary transition between South Hooe and Halton Quay fully freshwater conditions frequently occur (Ware and Meadows, 2011).

Average sea temperature in Plymouth Sound is 8 degrees Celsius in the winter and 16 degrees Celsius in the summer. However, in the estuary this is more variable and highs of 24 degrees Celsius have been recorded (Cefas, 2014).


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

Intertidal biogenic reefsSupporting processes: physico-chemical propertiesMaintain the natural physico-chemical properties of the water.N/AThe physico-chemical properties that influence habitats include salinity, pH and temperature. They can act alone or in combination to affect habitats and their communities in different ways, depending on species-specific tolerances. In coastal habitats they can vary widely and can influence the abundance, distribution and composition of communities at relatively local scales. Changes in any of these properties, as a result of human activities, may impact habitats and the communities they support (Joint Nature Conservation Committee (JNCC), 2004). Mytilus edulis mussel beds form in both boreal and temperate climates in the northern and southern hemispheres. Although temperature limits their distribution, they appear to be tolerant of very cold conditions (even below freezing), but research demonstrates an upper threshold tolerance of 29 ⁰C (Holt et al., 1998), (Fariñas-Franco et al., 2014).
Site-specifics:

Salinity is variable within the site although it very rarely reaches full salinity. Between Devil’s Point and the Tamar Bridge on the Tamar Estuary salinity is typically between 20 and 30 ppt. In the upper estuary between Cargreen and South Hooe salinity is typically in the region of 5ppt and in the riverine estuary transition between South Hooe and Halton Quay fully freshwater conditions frequently occur (Ware and Meadows, 2011).

Average sea temperature in Plymouth Sound is 8 degrees Celsius in the winter and 16 degrees Celsius in the summer. However, in the estuary this is more variable and highs of 24 degrees Celsius have been recorded (Cefas, 2014).


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

Blue mussel (Mytilus edulis) bedsSupporting processes: physico-chemical propertiesMaintain the natural physico-chemical properties of the water.N/AThe physico-chemical properties that influence habitats include salinity, pH and temperature. They can act alone or in combination to affect habitats and their communities in different ways, depending on species-specific tolerances. In coastal habitats they can vary widely and can influence the abundance, distribution and composition of communities at relatively local scales. Changes in any of these properties, as a result of human activities, may impact habitats and the communities they support (Joint Nature Conservation Committee (JNCC), 2004). Modiolus modiolus is a boreal species and dense aggregations meet their southern limit around British shores, which suggests that it's vulnerable to higher temperatures, and its upper limit is lower than Mytilus edulis (Walne, 1958). Mytilus edulis mussel beds form in boreal and temperate climates in both northern and southern hemispheres. Although temperature limits their distribution, they appear to be tolerant of very cold conditions (even below freezing), but research demonstrates upper thresholds of 29 ⁰C (Holt et al., 1998), (Fariñas-Franco et al., 2014).
Site-specifics:

Salinity is variable within the site although it very rarely reaches full salinity. Between Devil’s Point and the Tamar Bridge on the Tamar Estuary salinity is typically between 20 and 30 ppt. In the upper estuary between Cargreen and South Hooe salinity is typically in the region of 5ppt and in the riverine estuary transition between South Hooe and Halton Quay fully freshwater conditions frequently occur (Ware and Meadows, 2011).

Average sea temperature in Plymouth Sound is 8 degrees Celsius in the winter and 16 degrees Celsius in the summer. However, in the estuary this is more variable and highs of 24 degrees Celsius have been recorded (Cefas, 2014).


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

Blue mussel (Mytilus edulis) bedsSupporting processes: physico-chemical propertiesMaintain the natural physico-chemical properties of the water.N/AThe physico-chemical properties that influence habitats include salinity, pH and temperature. They can act alone or in combination to affect habitats and their communities in different ways, depending on species-specific tolerances. In coastal habitats they can vary widely and can influence the abundance, distribution and composition of communities at relatively local scales. Changes in any of these properties, as a result of human activities, may impact habitats and the communities they support (Joint Nature Conservation Committee (JNCC), 2004). Mytilus edulis mussel beds form in both boreal and temperate climates in the northern and southern hemispheres. Although temperature limits their distribution, they appear to be tolerant of very cold conditions (even below freezing), but research demonstrates an upper threshold tolerance of 29 ⁰C (Holt et al., 1998), (Fariñas-Franco et al., 2014).
Site-specifics:

Salinity is variable within the site although it very rarely reaches full salinity. Between Devil’s Point and the Tamar Bridge on the Tamar Estuary salinity is typically between 20 and 30 ppt. In the upper estuary between Cargreen and South Hooe salinity is typically in the region of 5ppt and in the riverine estuary transition between South Hooe and Halton Quay fully freshwater conditions frequently occur (Ware and Meadows, 2011).

Average sea temperature in Plymouth Sound is 8 degrees Celsius in the winter and 16 degrees Celsius in the summer. However, in the estuary this is more variable and highs of 24 degrees Celsius have been recorded (Cefas, 2014).


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

Native oyster (Ostrea edulis)Supporting processes: physico-chemical propertiesMaintain the natural physico-chemical properties of the water.N/A

The physico-chemical properties that influence the species include salinity, pH and temperature. These abiotic factors can affect the species in different ways depending on species-specific tolerances. Temperature and salinity are closely linked and can act either alone or in combination and can ultimately determine the success of a population, most notably in coastal habitats. Changes in any of these properties, as a result of human activity, may also impact the supporting habitats and the food favoured by the species.

The filtration rates, metabolic rates and growth rates of juvenile and adult native oysters generally increase with temperature, and the optimal temperature is thought to be 17 °C (Jackson and Wilding, 2009). Temperature is also important for initiating spawning (Jackson and Wilding, 2009). Any rapid changes to temperature away from the ambient or natural temperature, as a result of human activity, may still have an impact, so a precautionary approach is advised.

Although native oysters are adapted to cope with different salinities, they do prefer more fully saline conditions (Laing et al., 2005). At low salinities native oysters stop feeding and they cannot withstand salinities below 2.3 psu (Jackson and Wilding, 2009). A decrease in seawater pH may affect the ability of native oysters to build thick shells, making them more susceptible to predation. The impacts of acidified water on different life stages have still not been fully investigated.


Site-specifics:

Although the GMA for the feature is recover, there is no evidence that this attribute is in need of recovery. The target has therefore been set at 'maintain.’

Salinity is variable within the site although it very rarely reaches full salinity. Between Devil’s Point and the Tamar Bridge on the Tamar Estuary salinity is typically between 20 and 30 ppt. In the upper estuary between Cargreen and South Hooe salinity is typically in the region of 5ppt and in the riverine estuary transition between South Hooe and Halton Quay fully freshwater conditions frequently occur (Ware and Meadows, 2011).

Average sea temperature in Plymouth Sound is 8 degrees Celsius in the winter and 16 degrees Celsius in the summer. However, in the estuary this is more variable and highs of 24 degrees Celsius have been recorded (Cefas, 2014).


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

Smelt (Osmerus eperlanus)Supporting processes: physico-chemical propertiesMaintain the natural physico-chemical properties of the water.N/AThe physico-chemical properties that influence the species include salinity, pH and temperature. These abiotic factors can affect the species in different ways depending on species-specific tolerances. Temperature and salinity are closely linked and can act either alone or in combination, and can ultimately determine the success of a population, most notably in coastal habitats. Changes in any of these properties, as a result of human activity, may also impact the supporting habitats and the food favoured by the species. Changes in the temperature of a water body can change the behaviour of fish, causing them to enter or leave it at different times of the year. Water temperature strongly influences water chemistry (eg dissolved oxygen levels) and biological processes, such as reproduction and metabolism. Spawning in smelt is linked to spring increases in water temperature. Water temperatures exceeding 5 °C are a trigger for spawning, although this figure is thought to be site-specific and can be higher in some sites. Freshwater flow combined with water temperature during egg development can be used to predict year class strength in smelt (Potts and Wootton, 1984). Smelt can tolerate a range of salinity levels from full salinity (30-40 psu), variable (18-40 psu), to low (<18 psu). Spawning usually takes place in freshwater at the head of the estuary. However, it has been recorded in areas of variable salinity near the tidal limit at sites including the Tamar. Smelt eggs and larvae will not survive salinities above 16%
Site-specifics:

Although the GMA for the feature is recover, there is no evidence that this attribute is in need of recovery. The target has therefore been set at 'maintain.’

Salinity is variable within the site although it very rarely reaches full salinity. Between Devil’s Point and the Tamar Bridge on the Tamar Estuary salinity is typically between 20 and 30 ppt. In the upper estuary between Cargreen and South Hooe salinity is typically in the region of 5ppt and in the riverine estuary transition between South Hooe and Halton Quay fully freshwater conditions frequently occur (Ware and Meadows, 2011).

Average sea temperature in Plymouth Sound is 8 degrees Celsius in the winter and 16 degrees Celsius in the summer. However, in the estuary this is more variable and highs of 24 degrees Celsius have been recorded (Cefas, 2014).


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

Intertidal coarse sedimentSupporting processes: sediment contaminantsRestrict surface sediment contaminants (<1cm from the surface) to below the OSPAR Environment Assessment Criteria (EAC) or Effects Range Low (ERL) threshold. For example, mean cadmium levels should be maintained below the ERL of 1.2 mg per kg.N/AVarious different contaminants are known to affect the species that live in, or on the surface of, sediments. These include heavy metals (Hg, As, Zn, Ni, Ch, Cd, etc), poly-aromatic hydrocarbons (PAHs), poly-chlorinated biphenyls (PCBs), organotins (TBT) and pesticides such as hexachlorobenzene. These can impact species sensitive to particular contaminants, degrading the community structure (eg heavy metals) and bioaccumulating within organisms, entering the marine food chain (eg PCBs) (OSPAR Commission, 2012).
Site-specifics:

Historical mining activities have resulted in contamination of the Lynher and Tamar waters and sediments to varying degrees by metalliferous compounds, such as zinc and copper (Curtis, 2010) (Curtis, 2010). Arsenic, lead, zinc and copper have also been shown to increase with sediment depth in St. John’s Lake SSSI, reflecting the decline from peak mining activity in the 19th century (Curtis, 2010).


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

Native oyster (Ostrea edulis)Supporting processes: sediment movement and hydrodynamic regimeMaintain all hydrodynamic and physical conditions such that natural water flow and sediment movement is not significantly altered or constrained.N/A

Sediment movement is influenced by tide and wave driven water flow. Natural movement of water and sediment should not be hindered. Hydrodynamic conditions include the speed and direction of wave and tidal currents, seabed shear stress and wave exposure. Alterations to these processes could affect species presences and distribution.

Oysters are primarily subtidal although low intertidal populations exist. They can only feed when the tide is in so any changes to the times they are exposed could affect feeding opportunities (Jackson and Wilding, 2009).

Water movement needs to be maintained in order to provide the resources and support the various life processes of the native oyster. These include food and oxygen availability, the transport of larvae for recruitment, waste removal and the prevention of sediment build-up that can bury the oysters and reduce their feeding / breathing efficiency. Increases in water flow rate may interfere with settlement of spat, so flow is also an important consideration for larval retention (Kamphausen, 2012). Smothering by 5cm of sediment would prevent the flow of water through the oyster that permits respiration, feeding and removal of waste (Jackson and Wilding, 2009). However, even smaller increases may have an impact, and have been found to reduce growth rates (Jackson and Wilding, 2009). A layer of settled material of 1-2 mm in depth was reported to prevent satisfactory settlement of oyster spat on the substrate (Jackson and Wilding, 2009).


Site-specifics:

Although the GMA for the feature is recover, there is no evidence that this attribute is in need of recovery. The target has therefore been set at 'maintain.’


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

Smelt (Osmerus eperlanus)Supporting processes: sediment movement and hydrodynamic regimeMaintain all hydrodynamic and physical conditions such that natural water flow and sediment movement is not significantly altered or constrained.N/ASediment movement is influenced by tide and wave-driven water flow. Natural movement of water and sediment should not be hindered. Hydrodynamic conditions include the speed and direction of wave and tidal currents, seabed shear stress and wave exposure. Alterations to these processes could affect the presence and distribution of species. European smelt lay eggs in subtidal areas with a preference for areas with increased tidal and river flows (Colclough and Coates, 2013). Freshwater flow, combined with water temperature during egg development, can be used to predict year class strength. Maintaining the characteristic structure of habitats shaped by natural processes provides the diversity of water depths and current velocities necessary to fulfil the spawning, juvenile, adult and migratory requirements of this species. The maintenance of flow regime is critical to all aspects of the smelt’s life cycle, including migratory passage through the estuary to the spawning grounds, egg incubation, fry development and downstream migration. Practical management, to ensure natural processes such as river flow can be maintained, may include managing water abstractions upstream of the site. Preventing excessive sediment delivery from agricultural and other processes will reduce nuisance algal and fungal growth, and help to maintain a healthy habitat for this species. Spawning grounds are often at risk from silting, which can directly or indirectly result in the loss of habitat.
Site-specifics:

No site specific information.


The target has been set using expert judgement based on knowledge of the sensitivity of the feature to activities that are occurring / have occurred on the site.

Intertidal coarse sedimentSupporting processes: sediment movement and hydrodynamic regimeMaintain sediment transport pathways to and from the feature to ensure replenishment of habitats that rely on the sediment supply.N/ASedimentary habitats are often influenced by tide and wave-driven water flow that drives the movement or stability of sediment on and in areas surrounding the feature. These flow regimes can control both the shape and size of the feature, in addition to its sedimentary characteristics and biological composition. It's important that these hydrodynamic and sedimentary processes persist and are allowed to change in response to environmental conditions without hindrance. Hydrodynamic conditions include the speed and direction of wave and tidal currents, seabed shear stress and wave exposure (Little, 2000), (Elliott et al., 1998).
Site-specifics:

Each day in the Tamar the tide mobilises an average of 5,000 m3 of sediment in the upper reaches between Halton Quay and Gunnislake. Seasonally, changes in river flow cause an estimated 164,000 m3 of sediment to move up the estuary in summer and down again in winter. Storms can cause in the order of 30,000 m3 to be redistributed within the estuary in a few days (PMA, 2004).

The sediment budget within the estuary is thought to be reasonably well balanced. The main source of sediment is from riverine inputs, the main export is from dredge disposal outside of the site. It is currently understood that there is very little sediment exchange between the Plymouth Estuary system and the open sea. Sediment is thought to largely remain within the estuary and is gradually reworked unless it is removed by dredging activity (PMA, 2004) (Halcrow Group Ltd. , 2011). Calculations indicate that there has been a small net loss of sediment from the estuary over the last century which has been attributed to historic dredging to deepen the main channel. It is not thought that this sediment removal has had a significant impact on the intertidal mud extent or general tidal hydrodynamics of the estuary (PMA, 2004).


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

Intertidal biogenic reefsSupporting processes: sedimentation rateMaintain the natural rate of sediment deposition.N/AThe rate of sediment deposition is known to influence the status of reef habitats and / or their associated communities. Sedimentation on reefs can influence community composition, alter species growth rates and potentially impact reproductive success by affecting larval recruitment. An excessive accumulation of sediment can be detrimental to mussels (Seed and Suchanek, 1992). Mussels are able to move some distance to change their position within a bed or to resurface when buried by sand (Holt et al., 1998). They are relatively tolerant of short-term and repeated burial, with mortality increasing with increases in the percentage of re-suspended, finer sediments (Last et al., 2011). Young mussels can move upwards but many will suffocate (Dare, 1976), (Fariñas-Franco et al., 2014).
Site-specifics:

No site specific information.


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

Blue mussel (Mytilus edulis) bedsSupporting processes: sedimentation rateMaintain the natural rate of sediment deposition.N/AThe rate of sediment deposition is known to influence the status of reef habitats and / or their associated communities. Sedimentation on reefs can influence community composition, alter species growth rates and potentially impact reproductive success by affecting larval recruitment. An excessive accumulation of sediment can be detrimental to mussels (Seed and Suchanek, 1992). Mussels are able to move some distance to change their position within a bed or to resurface when buried by sand (Holt et al., 1998). They are relatively tolerant of short-term and repeated burial, with mortality increasing with increases in the percentage of re-suspended, finer sediments (Last et al., 2011). Young mussels can move upwards but many will suffocate (Dare, 1976), (Fariñas-Franco et al., 2014).
Site-specifics:

No site specific information.


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

Blue mussel (Mytilus edulis) bedsSupporting processes: sedimentation rateMaintain the natural rate of sediment deposition.N/AThe rate of sediment deposition is known to influence the status of reef habitats and / or their associated communities. Sedimentation on reefs can influence community composition, alter species growth rates and potentially impact reproductive success by affecting larval recruitment. An excessive accumulation of sediment can be detrimental to mussels (Seed and Suchanek, 1992). Mussels are able to move some distance to change their position within a bed, or to resurface when buried by sand (Holt et al., 1998). They are relatively tolerant of short-term and repeated burial, with mortality increasing with increases in the percentage of re-suspended, finer sediments (Last et al., 2011). Young mussels can move upwards but many will suffocate (Dare, 1976), (Fariñas-Franco et al., 2014).
Site-specifics:

No site specific information.


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

Blue mussel (Mytilus edulis) bedsSupporting processes: water movement and energyMaintain the natural water flow velocity to the intertidal mussel beds, to provide high levels of oxygen and food and prevent ‘mussel mud’ forming.N/AWater movement needs to be maintained in order to provide the resources and support the various life processes of an intertidal mussel bed. These include food and oxygen availability, the transport of larvae for recruitment, waste removal and the prevention of sediment build-up that reduces the efficiency of feeding / breathing.
Site-specifics:

Peak tidal current speed within the Tamar reaches a maximum 20 km upstream of the Narrows. Timing of the peak flood current velocity is progressively later with distance towards the head of the estuary. Flood currents are significantly greater than ebb currents, with the duration of the ebb longer than that of the flood (Debut, 2007).


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

Intertidal biogenic reefsSupporting processes: water movement and energyMaintain the natural water flow velocity to the intertidal mussel beds, to provide high levels of oxygen and food and prevent ‘mussel mud’ forming.N/AWater movement needs to be maintained in order to provide the resources and support the various life processes of an intertidal mussel bed. These include food and oxygen availability, the transport of larvae for recruitment, waste removal and the prevention of sediment build-up that reduces the efficiency of feeding / breathing.
Site-specifics:

Peak tidal current speed within the Tamar reaches a maximum 20 km upstream of the Narrows. Timing of the peak flood current velocity is progressively later with distance towards the head of the estuary. Flood currents are significantly greater than ebb currents, with the duration of the ebb longer than that of the flood (Debut, 2007).


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

Blue mussel (Mytilus edulis) bedsSupporting processes: water movement and energyMaintain the natural water flow velocity to the subtidal mussel beds, to provide high levels of oxygen and food and prevent ‘mussel mud’ forming.N/AWater movement needs to be maintained in order to provide the resources and support the various life processes of the subtidal mussel bed. These include food and oxygen availability, the transport of larvae for recruitment, waste removal and the prevention of sediment build-up that reduces the efficiency of feeding / breathing.
Site-specifics:

Peak tidal current speed within the Tamar reaches a maximum 20 km upstream of the Narrows. Timing of the peak flood current velocity is progressively later with distance towards the head of the estuary. Flood currents are significantly greater than ebb currents, with the duration of the ebb longer than that of the flood (Debut, 2007).


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

Blue mussel (Mytilus edulis) bedsSupporting processes: water quality - contaminantsRestrict aqueous contaminants to levels equating to High Status according to Annex VIII and Good Status according to Annex X of the Water Framework Directive, avoiding deterioration from existing levels.N/AContaminants may impact the ecology of the Marine Protected Area by having a range of biological effects on different species within the habitat, depending on the nature of the contaminant (Joint Nature Conservation Committee (JNCC), 2004), (UK Technical Advisory Group on the Water Framework Directive (UKTAG), 2008), (Environment Agency, 2014), (Fariñas-Franco et al., 2014).
Site-specifics:

Specific pollutants are listed on Annex VIII and X of the Water Framework Directive (WFD) and are assessed as part of the 'phys-chem' section of the ecological status. Thresholds vary for each, but for an example, the annual mean of arsenic should be <25µg per litre. The specific aqueous contaminants affecting the site are tributyltin compounds. Historical mining activities are thought to be the main source of chemical pollutants with contaminants contained within estuarine sediments and new inputs into the estuary coming from surface water draining from disused mines (Curtis, 2010) (Curtis, 2010) (Langston et al., 2003). In 1993 and 1994 high levels of Polycyclic Aromatic Hydrocarbons (PAHs) were detected in the Tamar (Hamoaze 376ng/L and off Warren Point 140ng/L) (Sheahan et al., 2007).


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

Blue mussel (Mytilus edulis) bedsSupporting processes: water quality - contaminantsRestrict aqueous contaminants to levels equating to High Status according to Annex VIII and Good Status according to Annex X of the Water Framework Directive, avoiding deterioration from existing levels.N/AContaminants may impact the ecology of the Marine Protected Area by having a range of biological effects on different species within the habitat, depending on the nature of the contaminant (Joint Nature Conservation Committee (JNCC), 2004), (UK Technical Advisory Group on the Water Framework Directive (UKTAG), 2008), (Environment Agency, 2014), (Fariñas-Franco et al., 2014).
Site-specifics:

Specific pollutants are listed on Annex VIII and X of the Water Framework Directive (WFD) and are assessed as part of the 'phys-chem' section of the ecological status. Thresholds vary for each, but for an example, the annual mean of arsenic should be <25µg per litre. The specific aqueous contaminants affecting the site are tributyltin compounds. Historical mining activities are thought to be the main source of chemical pollutants with contaminants contained within estuarine sediments and new inputs into the estuary coming from surface water draining from disused mines (Curtis, 2010) (Curtis, 2010) (Langston et al., 2003). In 1993 and 1994 high levels of Polycyclic Aromatic Hydrocarbons (PAHs) were detected in the Tamar (Hamoaze 376ng/L and off Warren Point 140ng/L) (Sheahan et al., 2007).


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

Native oyster (Ostrea edulis)Supporting processes: water quality - contaminantsRestrict aqueous contaminants to levels equating to High Status according to Annex VIII and Good Status according to Annex X of the Water Framework Directive, avoiding deterioration from existing levels.N/A

Contaminants may have a range of biological effects on the species, depending on the nature of the contaminant (Joint Nature Conservation Committee (JNCC), 2004), (UK Technical Advisory Group on the Water Framework Directive (UKTAG), 2008), (Environment Agency, 2014). Native oysters process large volumes of sea water and remove organic and inorganic particulates from the water column. Therefore, they are vulnerable to both water soluble contaminants and contaminants adsorbed onto particulates. Native oysters can bio accumulate Tributyltin (TBT), which can reduce growth of spat, prevent production of larvae and retard normal sex-change behaviour, thereby reducing population sizes (Jackson and Wilding, 2009).

Adult native oysters may have some tolerance to certain heavy metal pollution; the larval effects suggest that recruitment may be impaired resulting in a reduction in the population over time (Jackson and Wilding, 2009).


Site-specifics:

Although the GMA for the feature is recover, there is no evidence that this attribute is in need of recovery. The target has therefore been set at 'restrict’.

Specific pollutants are listed on Annex VIII and X of the Water Framework Directive (WFD) and are assessed as part of the 'phys-chem' section of the ecological status. Thresholds vary for each, but for an example, the annual mean of arsenic should be <25µg per litre. The specific aqueous contaminants affecting the site are tributyltin compounds. Historical mining activities are thought to be the main source of chemical pollutants with contaminants contained within estuarine sediments and new inputs into the estuary coming from surface water draining from disused mines (Curtis, 2010) (Curtis, 2010) (Langston et al., 2003). In 1993 and 1994 high levels of Polycyclic Aromatic Hydrocarbons (PAHs) were detected in the Tamar (Hamoaze 376ng/L and off Warren Point 140ng/L) (Sheahan et al., 2007).


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

Intertidal biogenic reefsSupporting processes: water quality - contaminantsRestrict aqueous contaminants to levels equating to High Status according to Annex VIII and Good Status according to Annex X of the Water Framework Directive, avoiding deterioration from existing levels.N/AContaminants may impact the ecology of the Marine Protected Area by having a range of biological effects on different species within the habitat, depending on the nature of the contaminant (Joint Nature Conservation Committee (JNCC), 2004), (UK Technical Advisory Group on the Water Framework Directive (UKTAG), 2008), (Environment Agency, 2014), (Fariñas-Franco et al., 2014).
Site-specifics:

Specific pollutants are listed on Annex VIII and X of the Water Framework Directive (WFD) and are assessed as part of the 'phys-chem' section of the ecological status. Thresholds vary for each, but for an example, the annual mean of arsenic should be <25µg per litre. The specific aqueous contaminants affecting the site are tributyltin compounds. Historical mining activities are thought to be the main source of chemical pollutants with contaminants contained within estuarine sediments and new inputs into the estuary coming from surface water draining from disused mines (Curtis, 2010) (Curtis, 2010) (Langston et al., 2003). In 1993 and 1994 high levels of Polycyclic Aromatic Hydrocarbons (PAHs) were detected in the Tamar (Hamoaze 376ng/L and off Warren Point 140ng/L) (Sheahan et al., 2007).


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

Intertidal coarse sedimentSupporting processes: water quality - contaminantsRestrict aqueous contaminants to levels equating to High Status according to Annex VIII and Good Status according to Annex X of the Water Framework Directive, avoiding deterioration from existing levels.N/AContaminants may impact the ecology of the Marine Protected Area by having a range of biological effects on different species within the habitat, depending on the nature of the contaminant (Joint Nature Conservation Committee (JNCC), 2004), (UK Technical Advisory Group on the Water Framework Directive (UKTAG), 2008), (Environment Agency, 2014).
Site-specifics:

Specific pollutants are listed on Annex VIII and X of the Water Framework Directive (WFD) and are assessed as part of the 'phys-chem' section of the ecological status. Thresholds vary for each, but for an example, the annual mean of arsenic should be <25µg per litre. The specific aqueous contaminants affecting the site are tributyltin compounds. Historical mining activities are thought to be the main source of chemical pollutants with contaminants contained within estuarine sediments and new inputs into the estuary coming from surface water draining from disused mines (Curtis, 2010) (Curtis, 2010) (Langston et al., 2003). In 1993 and 1994 high levels of Polycyclic Aromatic Hydrocarbons (PAHs) were detected in the Tamar (Hamoaze 376ng/L and off Warren Point 140ng/L) (Sheahan et al., 2007).


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

Smelt (Osmerus eperlanus)Supporting processes: water quality - contaminantsRestrict aqueous contaminants to levels equating to High Status according to Annex VIII and Good Status according to Annex X of the Water Framework Directive, avoiding deterioration from existing levels.N/AContaminants may have a range of biological effects on the species, depending on the nature of the contaminant (Joint Nature Conservation Committee (JNCC), 2004), (UK Technical Advisory Group on the Water Framework Directive (UKTAG), 2008), (Environment Agency, 2014). Smelt are sensitive to changes in water quality and are often used as an indicator. Smelt have been recorded as vulnerable to sewage, acidification, reductions in dissolved oxygen levels, nutrient enrichment and domestic and industrial discharges. However, information on thresholds is very limited. Smelt species are sensitive to a range of pollutants, which may have a range of lethal and sublethal effects. The synergistic effects of different metals are considered more important than the concentration of any single pollutant, and there is evidence that fish are negatively affected by heavy metal concentrations within compliant levels (Delpech et al., 2010). Because of this synergistic effect, pollutants and chemical levels below EQS levels may still cause lethal, sub-lethal and chronic effects. Poor water quality often leads to mortality or reduced abundance. One unknown source pollution event in The Shannon, Ireland resulted in a kill of 10,000 individuals. Pollution in the lower reaches of estuaries has been shown to prevent migration. Practical management, including direct management of activities within and outside the site that cause reductions in water quality (dissolved oxygen levels, pollution, etc) that may affect smelt, is therefore appropriate.
Site-specifics:

Although the GMA for the feature is recover, there is no evidence that this attribute is in need of recovery. The target has therefore been set at 'restrict.’

Specific pollutants are listed on Annex VIII and X of the Water Framework Directive (WFD) and are assessed as part of the 'phys-chem' section of the ecological status. Thresholds vary for each, but for an example, the annual mean of arsenic should be <25µg per litre. The specific aqueous contaminants affecting the site are tributyltin compounds. Historical mining activities are thought to be the main source of chemical pollutants with contaminants contained within estuarine sediments and new inputs into the estuary coming from surface water draining from disused mines (Curtis, 2010) (Curtis, 2010) (Langston et al., 2003). In 1993 and 1994 high levels of Polycyclic Aromatic Hydrocarbons (PAHs) were detected in the Tamar (Hamoaze 376ng/L and off Warren Point 140ng/L) (Sheahan et al., 2007).


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

Smelt (Osmerus eperlanus)Supporting processes: water quality - dissolved oxygenMaintain the Dissolved Oxygen (DO) concentration at levels equating to High Ecological Status (specifically ≥ 5.7 mg per litre (at 35 salinity) for 95 % of the year), avoiding deterioration from existing levelsN/ADissolved Oxygen (DO) levels affect the condition and health of species. Excessive nutrients and / or high turbidity can lead to a drop in DO, especially in warmer months. Low DO can have sub-lethal and lethal impacts on fish, and infauna and epifauna communities. However, there's a significant amount of natural variation that needs to be considered (Best et al., 2007), (Environment Agency Marine Monitoring Service, 2014). Barriers to migration can be created as a result of poor water quality. In particular, low levels of DO and can lead to smelt being excluded from important habitat (Maes et al., 2007). Studies in European estuaries suggest that smelt are among the more sensitive fish species in relation to DO. One study indicated smelt have a DO preference of >5 mg per litre (Möller and Scholz, 1991). Dissolved oxygen concentrations need to be considered in conjunction with other water quality variables, which will often operate together on fish physiology increasing their sensitivity to other contaminants, parasitism and predation. Low oxygen levels in water are often related to increased temperatures. Fish demand for oxygen and observed lethal limits of DO are known to increase with increasing temperature. In estuaries, the concentration of DO is strongly linked to the amount of suspended particulate matter, and increased levels of suspended sediments can cause deterioration in water quality (Bilotta and Brazier, 2008). Increases in suspended sediments often coincide with decreases in DO concentration, and similar to sensory behavioural barriers (noise, bubbles, sound, light), can act to interfere with or block the migration of diadromous fishes as they attempt to move through estuaries for spawning and feeding (Maes et al., 2007). In estuaries low levels of DO can arise naturally in the upper estuary where re-suspension of the sediment is maximised causing a sag in DO. This condition can be made worse by the input of organic matter from domestic sewage and industry, causing a water quality barrier.
Site-specifics:

Although the GMA for the feature is recover, there is no evidence that this attribute is in need of recovery. The target has therefore been set at 'maintain.’

Dissolved Oxygen (DO) in the site has been recorded at high status in 2009/10/12/13 and 2014 (Environment Agency Marine Monitoring Service, 2014).


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

Native oyster (Ostrea edulis)Supporting processes: water quality - dissolved oxygenMaintain the Dissolved Oxygen (DO) concentration at levels equating to High Ecological Status (specifically ≥ 5.7 mg per litre (at 35 salinity) for 95 % of the year), avoiding deterioration from existing levelsN/A

Dissolved Oxygen (DO) levels affect the condition and health of species. Excessive nutrients and / or high turbidity can lead to a drop in DO, especially in warmer months. Low DO can have sub-lethal and lethal effects on fish and infauna and epifauna communities. However, there’s a significant amount of natural variation that needs to be considered (Best et al., 2007), (Environment Agency Marine Monitoring Service, 2014). Reduced oxygen levels may be problematic for oysters if combined with reduced salinity. In such conditions the valves are kept closed as much as possible, limiting respiration.


Site-specifics:

Although the GMA for the feature is recover, there is no evidence that this attribute is in need of recovery. The target has therefore been set at 'maintain.’

Dissolved Oxygen (DO) in the site has been recorded at high status in 2009/10/12/13 and 2014 (Environment Agency Marine Monitoring Service, 2014).


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

Blue mussel (Mytilus edulis) bedsSupporting processes: water quality - dissolved oxygenMaintain the Dissolved Oxygen (DO) concentration at levels equating to High Ecological Status (specifically ≥ 5.7 mg per litre (at 35 salinity) for 95 % of the year), avoiding deterioration from existing levels.N/ADissolved Oxygen (DO) levels affect the condition and health of features. Excessive nutrients and / or high turbidity can lead to a drop in DO, especially in warmer months. Low DO can have sub-lethal and lethal impacts on fish and infauna and epifauna communities (Best et al., 2007). However, there’s a significant amount of natural variation that needs to be considered (Environment Agency Marine Monitoring Service, 2014), (Fariñas-Franco et al., 2014).
Site-specifics:

Dissolved Oxygen (DO) in the site has been recorded at high status in 2009/10/12/13 and 2014 (Environment Agency Marine Monitoring Service, 2014).


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

Intertidal coarse sedimentSupporting processes: water quality - dissolved oxygenMaintain the Dissolved Oxygen (DO) concentration at levels equating to High Ecological Status (specifically ≥ 5.7 mg per litre (at 35 salinity) for 95 % of the year), avoiding deterioration from existing levels.N/ADissolved Oxygen (DO) levels affect the condition and health of features. Excessive nutrients and / or high turbidity can lead to a drop in DO, especially in warmer months. Low DO can have sub-lethal and lethal impacts on fish and infauna and epifauna communities (Best et al., 2007). However, there’s a significant amount of natural variation that needs to be considered (Environment Agency Marine Monitoring Service, 2014).
Site-specifics:

Dissolved Oxygen (DO) in the site has been recorded at high status in 2009/10/12/13 and 2014 (Environment Agency Marine Monitoring Service, 2014).


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

Intertidal biogenic reefsSupporting processes: water quality - dissolved oxygenMaintain the Dissolved Oxygen (DO) concentration at levels equating to High Ecological Status (specifically ≥ 5.7 mg per litre (at 35 salinity) for 95 % of the year), avoiding deterioration from existing levels.N/ADissolved Oxygen (DO) levels affect the condition and health of features. Excessive nutrients and / or high turbidity can lead to a drop in DO, especially in warmer months. Low DO can have sub-lethal and lethal impacts on fish and infauna and epifauna communities. However, there’s a significant amount of natural variation that needs to be considered (Best et al., 2007), (Environment Agency Marine Monitoring Service, 2014), (Fariñas-Franco et al., 2014). (Hiscock et al., 2006)
Site-specifics:

Dissolved Oxygen (DO) in the site has been recorded at high status in 2009/10/12/13 and 2014 (Environment Agency Marine Monitoring Service, 2014).


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

Blue mussel (Mytilus edulis) bedsSupporting processes: water quality - dissolved oxygenMaintain the Dissolved Oxygen (DO) concentration at levels equating to High Ecological Status (specifically ≥ 5.7 mg per litre (at 35 salinity) for 95 % of the year)], avoiding deterioration from existing levels.N/ADissolved Oxygen (DO) levels affect the condition and health of features. Excessive nutrients and / or high turbidity can lead to a drop in DO, especially in warmer months. Low DO can have sub-lethal and lethal impacts on fish and infauna and epifauna communities. However, there’s a significant amount of natural variation that needs to be considered (Best et al., 2007), (Environment Agency Marine Monitoring Service, 2014), (Fariñas-Franco et al., 2014). (Hiscock et al., 2006)
Site-specifics:

Dissolved Oxygen (DO) in the site has been recorded at high status in 2009/10/12/13 and 2014 (Environment Agency Marine Monitoring Service, 2014).


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

Blue mussel (Mytilus edulis) bedsSupporting processes: water quality - nutrientsMaintain water quality at mean winter dissolved inorganic nitrogen levels where biological indicators of eutrophication (opportunistic macroalgal and phytoplankton blooms) do not affect the integrity of the site and features, avoiding deterioration from existing levels.N/AHigh concentrations of nutrients in the water column can cause phytoplankton and opportunistic macroalgae blooms, leading to reduced dissolved oxygen availability. These seaweeds can smother the sediment, preventing aeration and causing anoxia (lack of oxygen). This can impact sensitive fish, epifauna and infauna communities. The aim is to seek no further deterioration or improve water quality (Devlin et al., 2007), (Best, 2014). (Hiscock et al., 2006), (Fariñas-Franco et al., 2014)
Site-specifics:

The risk of eutrophication across the site has been assessed as low using the Environment Agency’s Weight of Evidence approach. This takes into account assessments of the Water Framework Directive opportunistic macroalgae and phytoplankton quality elements using the respective assessment tools. Adverse effects to integrity should be avoided. Therefore opportunistic macroalgal levels should be maintained so there is no adverse effect to the feature through limited algal cover (<15%) and low biomass (< 500 g m2) of macroalgal blooms in the available intertidal habitat, with area of available intertidal habitat affected by opportunistic macroalgae less than 15 %. There should also be limited (<5%) entrainment of algae in the underlying sediment (all accounting for seasonal variations and fluctuations in growth). Phytoplankton levels should be maintained above a WFD assessment tool score of 0.6, where there is only a minor (a) decline in species richness, and (b) disturbance to the diatom-dinoflagellate succession in the spring bloom compared to reference conditions.

In the past the area has been recorded as having a tendency towards being eutrophic and is moderately to highly vulnerable to nutrient enrichment. Monitoring of the site undertaken in summer 2010 found areas of green algal growth on intertidal mudflats, which is an indicator of excess nutrient input. Work has been undertaken through the Catchment Sensitive Farming project to reduce inputs as diffuse agricultural pollution was identified as the primary source in the site (Curtis, 2010) (Curtis, 2010) (Langston et al., 2003).


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

Blue mussel (Mytilus edulis) bedsSupporting processes: water quality - nutrientsMaintain water quality at mean winter dissolved inorganic nitrogen levels where biological indicators of eutrophication (opportunistic macroalgal and phytoplankton blooms) do not affect the integrity of the site and features, avoiding deterioration from existing levels.N/AHigh concentrations of nutrients in the water column can cause phytoplankton and opportunistic macroalgae blooms, leading to reduced dissolved oxygen availability. These seaweeds can smother the sediment, preventing aeration and causing anoxia (lack of oxygen). This can impact sensitive fish, epifauna and infauna communities. The aim is to seek no further deterioration or improve water quality (Devlin et al., 2007), (Best, 2014). (Fariñas-Franco et al., 2014)
Site-specifics:

The risk of eutrophication across the site has been assessed as low using the Environment Agency’s Weight of Evidence approach. This takes into account assessments of the Water Framework Directive opportunistic macroalgae and phytoplankton quality elements using the respective assessment tools. Adverse effects to integrity should be avoided. Therefore opportunistic macroalgal levels should be maintained so there is no adverse effect to the feature through limited algal cover (<15%) and low biomass (< 500 g m2) of macroalgal blooms in the available intertidal habitat, with area of available intertidal habitat affected by opportunistic macroalgae less than 15 %. There should also be limited (<5%) entrainment of algae in the underlying sediment (all accounting for seasonal variations and fluctuations in growth). Phytoplankton levels should be maintained above a WFD assessment tool score of 0.6, where there is only a minor (a) decline in species richness, and (b) disturbance to the diatom-dinoflagellate succession in the spring bloom compared to reference conditions.

In the past the area has been recorded as having a tendency towards being eutrophic and is moderately to highly vulnerable to nutrient enrichment. Monitoring of the site undertaken in summer 2010 found areas of green algal growth on intertidal mudflats, which is an indicator of excess nutrient input. Work has been undertaken through the Catchment Sensitive Farming project to reduce inputs as diffuse agricultural pollution was identified as the primary source in the site (Curtis, 2010) (Curtis, 2010) (Langston et al., 2003).


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

Native oyster (Ostrea edulis)Supporting processes: water quality - nutrientsMaintain water quality at mean winter dissolved inorganic nitrogen levels where biological indicators of eutrophication (opportunistic macroalgal and phytoplankton blooms) do not affect the integrity of the site and features, avoiding deterioration from existing levels.N/A

High concentrations of nutrients in the water column can cause phytoplankton and opportunistic macroalgae blooms, leading to reduced dissolved oxygen availability. These seaweeds can smother the sediment, preventing aeration and causing anoxia (lack of oxygen). This can impact sensitive fish, epifauna and infauna communities. The aim is to seek no further deterioration or improve water quality (Devlin et al., 2007), (Best, 2014).

Native oysters can do well in estuarine environments, which frequently have higher levels of nutrients than the open coast (Jackson and Wilding, 2009). Long-term or high levels of organic enrichment may have indirect adverse effects, such as increased turbidity, increased suspended sediment, increased risk of deoxygenation and the risk of algal blooms. Native oysters have been reported to suffer mortality due to algal blooms (Jackson and Wilding, 2009).


Site-specifics:

Although the GMA for the feature is recover, there is no evidence that this attribute is in need of recovery. The target has therefore been set at 'maintain.’

The risk of eutrophication across the site has been assessed as low using the Environment Agency’s Weight of Evidence approach. This takes into account assessments of the Water Framework Directive opportunistic macroalgae and phytoplankton quality elements using the respective assessment tools. Adverse effects to integrity should be avoided. Therefore opportunistic macroalgal levels should be maintained so there is no adverse effect to the feature through limited algal cover (<15%) and low biomass (< 500 g m2) of macroalgal blooms in the available intertidal habitat, with area of available intertidal habitat affected by opportunistic macroalgae less than 15 %. There should also be limited (<5%) entrainment of algae in the underlying sediment (all accounting for seasonal variations and fluctuations in growth). Phytoplankton levels should be maintained above a WFD assessment tool score of 0.6, where there is only a minor (a) decline in species richness, and (b) disturbance to the diatom-dinoflagellate succession in the spring bloom compared to reference conditions.

In the past the area has been recorded as having a tendency towards being eutrophic and is moderately to highly vulnerable to nutrient enrichment. Monitoring of the site undertaken in summer 2010 found areas of green algal growth on intertidal mudflats, which is an indicator of excess nutrient input. Work has been undertaken through the Catchment Sensitive Farming project to reduce inputs as diffuse agricultural pollution was identified as the primary source in the site (Curtis, 2010)(Curtis, 2010)(Langston et al., 2003).


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

Intertidal biogenic reefsSupporting processes: water quality - nutrientsMaintain water quality at mean winter dissolved inorganic nitrogen levels where biological indicators of eutrophication (opportunistic macroalgal and phytoplankton blooms) do not affect the integrity of the site and features, avoiding deterioration from existing levels.N/AHigh concentrations of nutrients in the water column can cause phytoplankton and opportunistic macroalgae blooms, leading to reduced dissolved oxygen availability. These seaweeds can smother the sediment, preventing aeration and causing anoxia (lack of oxygen). This can impact sensitive fish, epifauna and infauna communities. The aim is to seek no further deterioration or improve water quality (Devlin et al., 2007), (Best, 2014). (Hiscock et al., 2006), (Fariñas-Franco et al., 2014)
Site-specifics:

The risk of eutrophication across the site has been assessed as low using the Environment Agency’s Weight of Evidence approach. This takes into account assessments of the Water Framework Directive opportunistic macroalgae and phytoplankton quality elements using the respective assessment tools. Adverse effects to integrity should be avoided. Therefore opportunistic macroalgal levels should be maintained so there is no adverse effect to the feature through limited algal cover (<15%) and low biomass (< 500 g m2) of macroalgal blooms in the available intertidal habitat, with area of available intertidal habitat affected by opportunistic macroalgae less than 15 %. There should also be limited (<5%) entrainment of algae in the underlying sediment (all accounting for seasonal variations and fluctuations in growth). Phytoplankton levels should be maintained above a WFD assessment tool score of 0.6, where there is only a minor (a) decline in species richness, and (b) disturbance to the diatom-dinoflagellate succession in the spring bloom compared to reference conditions.

In the past the area has been recorded as having a tendency towards being eutrophic and is moderately to highly vulnerable to nutrient enrichment. Monitoring of the site undertaken in summer 2010 found areas of green algal growth on intertidal mudflats, which is an indicator of excess nutrient input. Work has been undertaken through the Catchment Sensitive Farming project to reduce inputs as diffuse agricultural pollution was identified as the primary source in the site (Curtis, 2010) (Curtis, 2010) (Langston et al., 2003).


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

Intertidal coarse sedimentSupporting processes: water quality - nutrientsMaintain water quality at mean winter dissolved inorganic nitrogen levels where biological indicators of eutrophication (opportunistic macroalgal and phytoplankton blooms) do not affect the integrity of the site and features, avoiding deterioration from existing levels.N/AHigh concentrations of nutrients in the water column can cause phytoplankton and opportunistic macroalgae blooms, leading to reduced dissolved oxygen availability. These seaweeds can smother the sediment, preventing aeration and causing anoxia (lack of oxygen). This can impact sensitive fish, epifauna and infauna communities. The aim is to seek no further deterioration or improve water quality (Devlin et al., 2007), (Best, 2014).
Site-specifics:

The risk of eutrophication across the site has been assessed as low using the Environment Agency’s Weight of Evidence approach. This takes into account assessments of the Water Framework Directive opportunistic macroalgae and phytoplankton quality elements using the respective assessment tools. Adverse effects to integrity should be avoided. Therefore opportunistic macroalgal levels should be maintained so there is no adverse effect to the feature through limited algal cover (<15%) and low biomass (< 500 g m2) of macroalgal blooms in the available intertidal habitat, with area of available intertidal habitat affected by opportunistic macroalgae less than 15 %. There should also be limited (<5%) entrainment of algae in the underlying sediment (all accounting for seasonal variations and fluctuations in growth). Phytoplankton levels should be maintained above a WFD assessment tool score of 0.6, where there is only a minor (a) decline in species richness, and (b) disturbance to the diatom-dinoflagellate succession in the spring bloom compared to reference conditions.

In the past the area has been recorded as having a tendency towards being eutrophic and is moderately to highly vulnerable to nutrient enrichment. Monitoring of the site undertaken in summer 2010 found areas of green algal growth on intertidal mudflats, which is an indicator of excess nutrient input. Work has been undertaken through the Catchment Sensitive Farming project to reduce inputs as diffuse agricultural pollution was identified as the primary source in the site (Curtis, 2010) (Curtis, 2010) (Langston et al., 2003).


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

Smelt (Osmerus eperlanus)Supporting processes: water quality - nutrientsMaintain water quality at mean winter dissolved inorganic nitrogen levels where biological indicators of eutrophication (opportunistic macroalgal and phytoplankton blooms) do not affect the integrity of the site and features, avoiding deterioration from existing levels.N/A

High concentrations of nutrients in the water column can cause phytoplankton and opportunistic macroalgae blooms, leading to reduced dissolved oxygen availability. These seaweeds can smother the sediment, preventing aeration and causing anoxia (lack of oxygen). This can impact sensitive fish, epifauna and infauna communities. The aim is to seek no further deterioration or improve water quality (Devlin et al., 2007), (Best, 2014).


Site-specifics:

Although the GMA for the feature is recover, there is no evidence that this attribute is in need of recovery. The target has therefore been set at 'maintain.’

The risk of eutrophication across the site has been assessed as low using the Environment Agency’s Weight of Evidence approach. This takes into account assessments of the Water Framework Directive opportunistic macroalgae and phytoplankton quality elements using the respective assessment tools. Adverse effects to integrity should be avoided. Therefore opportunistic macroalgal levels should be maintained so there is no adverse effect to the feature through limited algal cover (<15%) and low biomass (< 500 g m2) of macroalgal blooms in the available intertidal habitat, with area of available intertidal habitat affected by opportunistic macroalgae less than 15 %. There should also be limited (<5%) entrainment of algae in the underlying sediment (all accounting for seasonal variations and fluctuations in growth). Phytoplankton levels should be maintained above a WFD assessment tool score of 0.6, where there is only a minor (a) decline in species richness, and (b) disturbance to the diatom-dinoflagellate succession in the spring bloom compared to reference conditions.

In the past the area has been recorded as having a tendency towards being eutrophic and is moderately to highly vulnerable to nutrient enrichment. Monitoring of the site undertaken in summer 2010 found areas of green algal growth on intertidal mudflats, which is an indicator of excess nutrient input. Work has been undertaken through the Catchment Sensitive Farming project to reduce inputs as diffuse agricultural pollution was identified as the primary source in the site (Curtis, 2010) (Curtis, 2010) (Langston et al., 2003).


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

Blue mussel (Mytilus edulis) bedsSupporting processes: water quality - turbidityMaintain natural levels of turbidity (eg concentrations of suspended sediment, plankton and other material) across the habitat.N/AWater turbidity is a result of material suspended in the water, including sediment, plankton, pollution or other matter washed into the sea from land sources. In coastal environments turbidity levels can rise and fall rapidly as a result of biological (eg plankton blooms), physical (eg storm events) or human (eg coastal development) factors. Prolonged changes in turbidity may influence the amount of light reaching the seabed, affecting the primary production and nutrient levels of the habitat’s associated communities. Changes in turbidity may also have a range of biological effects on different species within the habitat, eg affecting their abilities to feed or breathe (Joint Nature Conservation Committee (JNCC), 2004), (Fariñas-Franco et al., 2014).
Site-specifics:

The estuary turbidity maxima for the Tamar normally occurs in the low salinity upper reaches. It is characterised by fine sediment in suspension (50 to 100μm particle diameter). Suspended sediment concentrations from the lower Tamar estuary showed a background concentration of 0.02 kg m−3 throughout most of the spring–neap cycle. On spring tides the depth-averaged concentration increased to 0.25–0.40 kg m−3 (Tattersall et al., 2003).

The turbidity maxima is normally associated with the fresh/saltwater interface, but occasionally occurs further upstream. During summer, the peak turbidity maxima is normally encountered close to Gunnislake weir (0 to 10km). However, in winter it moves down estuary between 15 to 25 km from the weir. At 25km from the weir, the turbidity maxima is located between Saltash Bridge (24 km) and Weston Mill Lake (26 km). The movement of the turbidity maxima appears to be associated with changes in river flow (Debut, 2007).


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

Blue mussel (Mytilus edulis) bedsSupporting processes: water quality - turbidityMaintain natural levels of turbidity (eg suspended concentrations of sediment, plankton and other material) across the habitat.N/AWater turbidity is a result of material suspended in the water, including sediment, plankton, pollution or other matter washed into the sea from land sources. In coastal environments turbidity levels can rise and fall rapidly as a result of biological (eg plankton blooms), physical (eg storm events) or human (eg coastal development) factors. Prolonged changes in turbidity may influence the amount of light reaching the seabed, affecting the primary production and nutrient levels of the habitat’s associated communities. Changes in turbidity may also have a range of biological effects on different species within the habitat, eg affecting their abilities to feed or breathe (Joint Nature Conservation Committee (JNCC), 2004), (Fariñas-Franco et al., 2014).
Site-specifics:

The estuary turbidity maxima for the Tamar normally occurs in the low salinity upper reaches. It is characterised by fine sediment in suspension (50 to 100μm particle diameter). Suspended sediment concentrations from the lower Tamar estuary showed a background concentration of 0.02 kg m−3 throughout most of the spring–neap cycle. On spring tides the depth-averaged concentration increased to 0.25–0.40 kg m−3 (Tattersall et al., 2003).

The turbidity maxima is normally associated with the fresh/saltwater interface, but occasionally occurs further upstream. During summer, the peak turbidity maxima is normally encountered close to Gunnislake weir (0 to 10km). However, in winter it moves down estuary between 15 to 25 km from the weir. At 25km from the weir, the turbidity maxima is located between Saltash Bridge (24 km) and Weston Mill Lake (26 km). The movement of the turbidity maxima appears to be associated with changes in river flow (Debut, 2007).


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

Intertidal coarse sedimentSupporting processes: water quality - turbidityMaintain natural levels of turbidity (eg suspended concentrations of sediment, plankton and other material) across the habitat.N/AWater turbidity is a result of material suspended in the water, including sediment, plankton, pollution or other matter washed into the sea from land sources. In coastal environments turbidity levels can rise and fall rapidly as a result of biological (eg plankton blooms), physical (eg storm events) or human (eg coastal development) factors. Prolonged changes in turbidity may influence the amount of light reaching the seabed, affecting the primary production and nutrient levels of the habitat’s associated communities. Changes in turbidity may also have a range of biological effects on different species within the habitat, eg affecting their abilities to feed or breathe. A prolonged increase in turbidity is indicative of an increase in suspended particulates. This has a number of implications for the marine environment, such as affecting fish health, clogging the filtering organs of suspension feeding animals and affecting seabed sedimentation rates (Elliott et al., 1998).
Site-specifics:

The estuary turbidity maxima for the Tamar normally occurs in the low salinity upper reaches. It is characterised by fine sediment in suspension (50 to 100μm particle diameter). Suspended sediment concentrations from the lower Tamar estuary showed a background concentration of 0.02 kg m−3 throughout most of the spring–neap cycle. On spring tides the depth-averaged concentration increased to 0.25–0.40 kg m−3 (Tattersall et al., 2003).

The turbidity maxima is normally associated with the fresh/saltwater interface, but occasionally occurs further upstream. During summer, the peak turbidity maxima is normally encountered close to Gunnislake weir (0 to 10km). However, in winter it moves down estuary between 15 to 25 km from the weir. At 25km from the weir, the turbidity maxima is located between Saltash Bridge (24 km) and Weston Mill Lake (26 km). The movement of the turbidity maxima appears to be associated with changes in river flow (Debut, 2007).


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

Intertidal biogenic reefsSupporting processes: water quality - turbidityMaintain natural levels of turbidity (eg suspended concentrations of sediment, plankton and other material) across the habitat.N/AWater turbidity is a result of material suspended in the water, including sediment, plankton, pollution or other matter washed into the sea from land sources. In coastal environments turbidity levels can rise and fall rapidly as a result of biological (eg plankton blooms), physical (eg storm events) or human (eg coastal development) factors. Prolonged changes in turbidity may influence the amount of light reaching the seabed, affecting the primary production and nutrient levels of the habitat’s associated communities. Changes in turbidity may also have a range of biological effects on different species within the habitat, eg affecting their abilities to feed or breathe (Joint Nature Conservation Committee (JNCC), 2004), (Fariñas-Franco et al., 2014).
Site-specifics:

The estuary turbidity maxima for the Tamar normally occurs in the low salinity upper reaches. It is characterised by fine sediment in suspension (50 to 100μm particle diameter). Suspended sediment concentrations from the lower Tamar estuary showed a background concentration of 0.02 kg m−3 throughout most of the spring–neap cycle. On spring tides the depth-averaged concentration increased to 0.25–0.40 kg m−3 (Tattersall et al., 2003).

The turbidity maxima is normally associated with the fresh/saltwater interface, but occasionally occurs further upstream. During summer, the peak turbidity maxima is normally encountered close to Gunnislake weir (0 to 10km). However, in winter it moves down estuary between 15 to 25 km from the weir. At 25km from the weir, the turbidity maxima is located between Saltash Bridge (24 km) and Weston Mill Lake (26 km). The movement of the turbidity maxima appears to be associated with changes in river flow (Debut, 2007).


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

Native oyster (Ostrea edulis)Supporting processes: water quality - turbidityMaintain natural levels of turbidity (eg suspended concentrations of sediment, plankton and other material) in areas where this species is, or could be present.N/A

Water turbidity is a result of material suspended in the water, including sediment, plankton, pollution or other matter washed into the sea from land sources. In coastal environments turbidity levels can rise and fall rapidly as a result of biological (eg plankton blooms), physical (eg storm events) or human (eg coastal development) factors. Prolonged increases in turbidity could affect the ability of the species to feed and respire.

Native oysters respond to an increase in suspended sediment by increasing pseudofaeces production and the expulsion of accumulated silt, both of which exert an energetic cost (Jackson and Wilding, 2009). Suspended sediment has also been shown to reduce the growth rate of adult native oysters, resulting in shell thickening. Filtration can be completely inhibited by 10 mg per litre of particulate organic matter and significantly reduced by 5 mg per litre (Jackson and Wilding, 2009). An increase in suspended sediment may have longer term effects on the population by inhibiting spatfall. Increased turbidity and decreased light penetration may decrease primary production by phytoplankton, and therefore alter food availability.


Site-specifics:

Although the GMA for the feature is recover, there is no evidence that this attribute is in need of recovery. The target has therefore been set at 'maintain.’

The estuary turbidity maxima for the Tamar normally occurs in the low salinity upper reaches. It is characterised by fine sediment in suspension (50 to 100μm particle diameter). Suspended sediment concentrations from the lower Tamar estuary showed a background concentration of 0.02 kg m−3 throughout most of the spring–neap cycle. On spring tides the depth-averaged concentration increased to 0.25–0.40 kg m−3 (Tattersall et al., 2003).

The turbidity maxima is normally associated with the fresh/saltwater interface, but occasionally occurs further upstream. During summer, the peak turbidity maxima is normally encountered close to Gunnislake weir (0 to 10km). However, in winter it moves down estuary between 15 to 25 km from the weir. At 25km from the weir, the turbidity maxima is located between Saltash Bridge (24 km) and Weston Mill Lake (26 km). The movement of the turbidity maxima appears to be associated with changes in river flow (Debut, 2007).


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

Smelt (Osmerus eperlanus)Supporting processes: water quality - turbidityMaintain natural levels of turbidity (eg suspended concentrations of sediment, plankton and other material) in areas where this species is, or could be present.N/AWater turbidity is a result of material suspended in the water, including sediment, plankton, pollution, or other matter washed into the sea from land sources. In coastal environments turbidity levels can rise and fall rapidly as a result of biological (eg plankton blooms), physical (eg storm events) or human (eg coastal development) factors. Prolonged increases in turbidity could impact the ability of the species to feed and respire.
Site-specifics:

Although the GMA for the feature is recover, there is no evidence that this attribute is in need of recovery. The target has therefore been set at 'maintain.’

The estuary turbidity maxima for the Tamar normally occurs in the low salinity upper reaches. It is characterised by fine sediment in suspension (50 to 100μm particle diameter). Suspended sediment concentrations from the lower Tamar estuary showed a background concentration of 0.02 kg m−3 throughout most of the spring–neap cycle. On spring tides the depth-averaged concentration increased to 0.25–0.40 kg m−3 (Tattersall et al., 2003).

The turbidity maxima is normally associated with the fresh/saltwater interface, but occasionally occurs further upstream. During summer, the peak turbidity maxima is normally encountered close to Gunnislake weir (0 to 10km). However, in winter it moves down estuary between 15 to 25 km from the weir. At 25km from the weir, the turbidity maxima is located between Saltash Bridge (24 km) and Weston Mill Lake (26 km). The movement of the turbidity maxima appears to be associated with changes in river flow (Debut, 2007).


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

The targets given for each attribute do not represent thresholds to assess the significance of any given impact in MCZ assessments. You will need to assess this on a case-by-case basis using the most current information available. See further guidance on how to undertake an assessment of implications of a proposal on a MCZ is given in Marine Conservation Zones and Marine Licensing.

These tables bring together the findings of the best available scientific evidence which may be updated or supplemented in further publications from Natural England and other sources. You may decide to use other additional sources of information.

These tables do not give advice about other legally protected species which may also be present within the MCZ.