The Marine Life Information Network

Global warming (extreme)

Extreme emission scenario (by the end of this century 2081-2100) benchmark of:

• A 5°C rise in SST and NBT (coastal to the shelf seas),

• A 6°C rise in surface air temperature (in eulittoral and supralittoral habitats).

• A 1°C rise in Deep-sea habitats (>200 m) off the continental shelf, and

• A 5°C rise in surface air temperature in intertidal habitats exclusive to Scotland. Further detail.

Evidence

This biotope is characterized by a scarcity of species resulting from sediment mobility and abrasion (JNCC, 2015).  Therefore, changes in temperature will not alter the biotope as it is defined by the abiotic habitat, i.e. wave exposure and water flow, and the sparse fauna are transient or opportunistic.  Nevertheless, most of the species recorded in the biotope have a broad range from Norway, the North East Atlantic (NEA) and into the Mediterranean (e.g. Gastrosaccus spinifera, Nephthys cirrosa, Eurydice pelagic, and Pontocrates arenarius) (OBIS, 2019) and may be able to tolerate the predicted increase in temperature.  However, Bathyporeia pelagica is only recorded from the NEA and Urothoe brevicornis is mainly recorded from the southern North Sea, and the Irish, and Celtic Seas.  Emery et al. (1957) reported that Nephtys spp. could withstand summer temperatures of 30-35°C.  Adult males and gravid females of Bathyporeia pelagica had upper lethal temperature tolerances of 33.4 and 34.2°C respectively, after 24 hrs exposure in the laboratory (Preece, 1971).  Although Bathyporeia spp. may survive high temperatures in the short-term, species from the genus Bathyporeia are known to have a limited geographical distribution, occurring northwards of the Bay of Biscay where summer temperatures reach 22°C (Koutsikopoulos et al., 1998), which suggest that this may be a cut off point for proliferation of this species.

Sensitivity assessment.  Sea surface temperatures around the UK currently fall between 6-19°C (Huthnance, 2010). Therefore, the middle, high and extreme scenarios may result in increase in average temperatures to 22, 23, or 24°C by the end of the century.  Most of the species recorded in this biotope would probably tolerant increases to these levels, especially if they have time to acclimate to the change, or adapt given their short generation time. Urothoe brevicornis may even extend its range northwards also no evidence of range expansion in these species was found. However, Bathyporeia spp. might be expected to decline in southern examples of this biotope.

Nevertheless, the fauna are transient or opportunistic species washed in and out of the biotope by wave action, highly mobile and/or capable of rapid reproduction and, while the relative abundance of different amphipods and isopods may change, the characteristic biotope will probably remain the same.  Hence, resistance to an increase in temperature under the middle, high, and extreme scenarios is assessed as 'High' and resilience as ‘High’ (by default) and this biotope is assessed as 'Not sensitive'.

Global warming (high)

High emission scenario (by the end of this century 2081-2100) benchmark of:

• A 4°C rise in SST, NBT (coastal to the shelf seas) and surface air temperature (in eulittoral and supralittoral habitats).

• A 1°C rise in Deep-sea habitats (>200 m) off the continental shelf, and

• A 3°C rise in surface air temperature in intertidal habitats exclusive to Scotland. Further detail.

Evidence

This biotope is characterized by a scarcity of species resulting from sediment mobility and abrasion (JNCC, 2015).  Therefore, changes in temperature will not alter the biotope as it is defined by the abiotic habitat, i.e. wave exposure and water flow, and the sparse fauna are transient or opportunistic.  Nevertheless, most of the species recorded in the biotope have a broad range from Norway, the North East Atlantic (NEA) and into the Mediterranean (e.g. Gastrosaccus spinifera, Nephthys cirrosa, Eurydice pelagic, and Pontocrates arenarius) (OBIS, 2019) and may be able to tolerate the predicted increase in temperature.  However, Bathyporeia pelagica is only recorded from the NEA and Urothoe brevicornis is mainly recorded from the southern North Sea, and the Irish, and Celtic Seas.  Emery et al. (1957) reported that Nephtys spp. could withstand summer temperatures of 30-35°C.  Adult males and gravid females of Bathyporeia pelagica had upper lethal temperature tolerances of 33.4 and 34.2°C respectively, after 24 hrs exposure in the laboratory (Preece, 1971).  Although Bathyporeia spp. may survive high temperatures in the short-term, species from the genus Bathyporeia are known to have a limited geographical distribution, occurring northwards of the Bay of Biscay where summer temperatures reach 22°C (Koutsikopoulos et al., 1998), which suggest that this may be a cut off point for proliferation of this species.

Sensitivity assessment.  Sea surface temperatures around the UK currently fall between 6-19°C (Huthnance, 2010). Therefore, the middle, high and extreme scenarios may result in increase in average temperatures to 22, 23, or 24°C by the end of the century.  Most of the species recorded in this biotope would probably tolerant increases to these levels, especially if they have time to acclimate to the change, or adapt given their short generation time. Urothoe brevicornis may even extend its range northwards also no evidence of range expansion in these species was found. However, Bathyporeia spp. might be expected to decline in southern examples of this biotope.

Nevertheless, the fauna are transient or opportunistic species washed in and out of the biotope by wave action, highly mobile and/or capable of rapid reproduction and, while the relative abundance of different amphipods and isopods may change, the characteristic biotope will probably remain the same.  Hence, resistance to an increase in temperature under the middle, high, and extreme scenarios is assessed as 'High' and resilience as ‘High’ (by default) and this biotope is assessed as 'Not sensitive'.

Global warming (middle)

Middle emission scenario (by the end of this century 2081-2100) benchmark of:

• A 3°C rise in SST, NBT (coastal to the shelf seas) and surface air temperature (in eulittoral and supralittoral habitats).

• A 1°C rise in Deep-sea habitats (>200 m) off the continental shelf.

• A 2°C rise in surface air temperature in intertidal habitats exclusive to Scotland. Further detail.

Evidence

This biotope is characterized by a scarcity of species resulting from sediment mobility and abrasion (JNCC, 2015).  Therefore, changes in temperature will not alter the biotope as it is defined by the abiotic habitat, i.e. wave exposure and water flow, and the sparse fauna are transient or opportunistic.  Nevertheless, most of the species recorded in the biotope have a broad range from Norway, the North East Atlantic (NEA) and into the Mediterranean (e.g. Gastrosaccus spinifera, Nephthys cirrosa, Eurydice pelagic, and Pontocrates arenarius) (OBIS, 2019) and may be able to tolerate the predicted increase in temperature.  However, Bathyporeia pelagica is only recorded from the NEA and Urothoe brevicornis is mainly recorded from the southern North Sea, and the Irish, and Celtic Seas.  Emery et al. (1957) reported that Nephtys spp. could withstand summer temperatures of 30-35°C.  Adult males and gravid females of Bathyporeia pelagica had upper lethal temperature tolerances of 33.4 and 34.2°C respectively, after 24 hrs exposure in the laboratory (Preece, 1971).  Although Bathyporeia spp. may survive high temperatures in the short-term, species from the genus Bathyporeia are known to have a limited geographical distribution, occurring northwards of the Bay of Biscay where summer temperatures reach 22°C (Koutsikopoulos et al., 1998), which suggest that this may be a cut off point for proliferation of this species.

Sensitivity assessment.  Sea surface temperatures around the UK currently fall between 6-19°C (Huthnance, 2010). Therefore, the middle, high and extreme scenarios may result in increase in average temperatures to 22, 23, or 24°C by the end of the century.  Most of the species recorded in this biotope would probably tolerant increases to these levels, especially if they have time to acclimate to the change, or adapt given their short generation time. Urothoe brevicornis may even extend its range northwards also no evidence of range expansion in these species was found. However, Bathyporeia spp. might be expected to decline in southern examples of this biotope.

Nevertheless, the fauna are transient or opportunistic species washed in and out of the biotope by wave action, highly mobile and/or capable of rapid reproduction and, while the relative abundance of different amphipods and isopods may change, the characteristic biotope will probably remain the same.  Hence, resistance to an increase in temperature under the middle, high, and extreme scenarios is assessed as 'High' and resilience as ‘High’ (by default) and this biotope is assessed as 'Not sensitive'.

Marine heatwaves (high)

High emission scenario benchmark: A marine heatwave occurring every two years, with a mean duration of 120 days, and a maximum intensity of 3.5°C. Further detail.

Evidence

This biotope is characterized by the absence of species resulting from sediment mobility and abrasion (JNCC, 2015), rather than the presence of typical species.  Therefore, changes in temperature will not alter the biotope as it is defined by the abiotic habitat, i.e. wave exposure and water flow, and the sparse fauna are transient or opportunistic.  Climate change also increase the intensity of extreme temperature events, exerting additional stress on ecosystems.

In Kiel Fjord, Baltic Sea, where temperatures generally range from 0-20°C, simulated marine heatwaves on natural communities (summer temperature increased to 25°C), led to an increase in biomass in two out of four species of polychaetes, whilst a decrease in both biomass and abundance was seen for a tube-dwelling polychaete (Polydora cornuta) (Pansch et al., 2018). In the same study the biomass of two of four amphipod species significantly increased, whilst no significant negative impacts were seen on either biomass or abundance of the other species. Curiously, the heatwaves experiments favoured burrowing and crawling species (e.g. amphipods and isopods) but the abundance of detritivores (e.g. the polychaetes examined) decreased.

Most of the species recorded in the biotope have a broad range from Norway, the North East Atlantic (NEA) and into the Mediterranean (e.g. Gastrosaccus spinifera, Nephthys cirrosa, Eurydice pelagic, and Pontocrates arenarius) (OBIS, 2019) and may be able to tolerate the increases in temperature.  However, Bathyporeia pelagica is only recorded from the NEA and Urothoe brevicornis is mainly recorded from the southern North Sea, the Irish, and Celtic Seas.  Emery et al. (1957) reported that Nephtys spp. could withstand summer temperatures of 30-35°C.  Adult males and gravid females of Bathyporeia pelagica had upper lethal temperature tolerances of 33.4 and 34.2°C respectively, after 24 hrs exposure in the laboratory (Preece, 1971).  Although Bathyporeia spp. may survive high temperatures in the short-term, species from the genus Bathyporeia are known to have a limited geographical distribution, occurring northwards of the Bay of Biscay where summer temperatures reach 22°C (Koutsikopoulos et al., 1998), which suggest that this may be a cut off point for proliferation of this species.

Sensitivity assessment.  Sea surface temperatures around the UK currently fall between 6-19°C (Huthnance, 2010). Under the middle emission scenario, if heatwaves occurred at a frequency of every three years, with heatwaves reaching a maximum intensity of 2°C for a period of 80 days, by the end of this century this could lead to sea temperatures reaching up to 24°C in southern England in summer months. It is likely that Nephtys cirrosa and the recorded amphipods and isopods Bathyporeia spp. would be able to withstand a heatwave of this intensity and duration.  Under the high emission scenario, if heatwaves occurred at a frequency of every two years, reaching a maximum intensity of 3.5°C for a period of 120 days by the end of this century, this could lead to the heatwave lasting the entire summer with temperatures reaching up to 26.5°C. Whilst it is likely that most of the resident species would be able to withstand this temperature, the fact that species from the genus Bathyporeia do not occur more southerly than the Bay of Biscay, suggests that this genus would not be able to adapt to sudden changes in temperature.

Nevertheless, the fauna are transient or opportunistic species washed in and out of the biotope by wave action, are highly mobile and/or capable of rapid reproduction and, while the relative abundance of different amphipods and isopods may change, the characteristic biotope will probably remain the same.  Hence, resistance to an increase in temperature under the middle, and high emission scenarios is assessed as 'High' and resilience as ‘High’ (by default) and this biotope is assessed as 'Not sensitive'

Marine heatwaves (middle)

Middle emission scenario benchmark:  A marine heatwave occurring every three years, with a mean duration of 80 days, with a maximum intensity of 2°C. Further detail.

Evidence

This biotope is characterized by the absence of species resulting from sediment mobility and abrasion (JNCC, 2015), rather than the presence of typical species.  Therefore, changes in temperature will not alter the biotope as it is defined by the abiotic habitat, i.e. wave exposure and water flow, and the sparse fauna are transient or opportunistic.  Climate change also increase the intensity of extreme temperature events, exerting additional stress on ecosystems.

In Kiel Fjord, Baltic Sea, where temperatures generally range from 0-20°C, simulated marine heatwaves on natural communities (summer temperature increased to 25°C), led to an increase in biomass in two out of four species of polychaetes, whilst a decrease in both biomass and abundance was seen for a tube-dwelling polychaete (Polydora cornuta) (Pansch et al., 2018). In the same study the biomass of two of four amphipod species significantly increased, whilst no significant negative impacts were seen on either biomass or abundance of the other species. Curiously, the heatwaves experiments favoured burrowing and crawling species (e.g. amphipods and isopods) but the abundance of detritivores (e.g. the polychaetes examined) decreased.

Most of the species recorded in the biotope have a broad range from Norway, the North East Atlantic (NEA) and into the Mediterranean (e.g. Gastrosaccus spinifera, Nephthys cirrosa, Eurydice pelagic, and Pontocrates arenarius) (OBIS, 2019) and may be able to tolerate the increases in temperature.  However, Bathyporeia pelagica is only recorded from the NEA and Urothoe brevicornis is mainly recorded from the southern North Sea, the Irish, and Celtic Seas.  Emery et al. (1957) reported that Nephtys spp. could withstand summer temperatures of 30-35°C.  Adult males and gravid females of Bathyporeia pelagica had upper lethal temperature tolerances of 33.4 and 34.2°C respectively, after 24 hrs exposure in the laboratory (Preece, 1971).  Although Bathyporeia spp. may survive high temperatures in the short-term, species from the genus Bathyporeia are known to have a limited geographical distribution, occurring northwards of the Bay of Biscay where summer temperatures reach 22°C (Koutsikopoulos et al., 1998), which suggest that this may be a cut off point for proliferation of this species.

Sensitivity assessment.  Sea surface temperatures around the UK currently fall between 6-19°C (Huthnance, 2010). Under the middle emission scenario, if heatwaves occurred at a frequency of every three years, with heatwaves reaching a maximum intensity of 2°C for a period of 80 days, by the end of this century this could lead to sea temperatures reaching up to 24°C in southern England in summer months. It is likely that Nephtys cirrosa and the recorded amphipods and isopods Bathyporeia spp. would be able to withstand a heatwave of this intensity and duration.  Under the high emission scenario, if heatwaves occurred at a frequency of every two years, reaching a maximum intensity of 3.5°C for a period of 120 days by the end of this century, this could lead to the heatwave lasting the entire summer with temperatures reaching up to 26.5°C. Whilst it is likely that most of the resident species would be able to withstand this temperature, the fact that species from the genus Bathyporeia do not occur more southerly than the Bay of Biscay, suggests that this genus would not be able to adapt to sudden changes in temperature.

Nevertheless, the fauna are transient or opportunistic species washed in and out of the biotope by wave action, are highly mobile and/or capable of rapid reproduction and, while the relative abundance of different amphipods and isopods may change, the characteristic biotope will probably remain the same.  Hence, resistance to an increase in temperature under the middle, and high emission scenarios is assessed as 'High' and resilience as ‘High’ (by default) and this biotope is assessed as 'Not sensitive'

Ocean acidification (high)

High emission scenario benchmark: a further decrease in pH of 0.35 (annual mean) and corresponding 120% increase in H+ ions , seasonal aragonite saturation of 20% of UK coastal waters and North Sea bottom waters, and the aragonite saturation horizon in the NE Atlantic, off the continental shelf, occurring at a depth of 400 m by the end of this century 2081-2100. Further detail 

Evidence

There is no direct evidence of the impact of ocean acidification on either Nephtys cirrosa or the amphipods and isopods that characterize this habitat. Amphipods are generally thought to be less sensitive to ocean acidification than other taxa and are actually found in greater numbers at naturally CO₂ enriched vents (Kroeker et al., 2011, Garrard et al., 2014, Vizzini et al., 2017). Much of this increase in abundance is not expected to be directly related to CO₂ enrichment but rather due to indirect effects such as reduced predation or increased food supply (Kroeker et al., 2011; Kroeker et al., 2013, Garrard et al., 2014). A laboratory study found that under identical conditions other than CO₂ enrichment, the population size of the amphipod Gammarus locusta increased 20 fold and the proportion of gravid females doubled, suggesting that ocean acidification may confer an advantage to amphipods by relaxing environmental constraints on reproduction (Heldt et al., 2016). Kroeker et al. (2011) also noted no significant decrease in isopod abundance in areas of naturally low pH of 7.8 or 6.6.  However, while Garrard et al. (2014) noted no significant decrease in isopod abundance, isopod species richness was significantly decreased at pH 7.8.  Further laboratory experiments show little effect of ocean acidification on amphipods at levels expected for the high emission scenario at the end of this century (pH 7.8) (Hauton et al., 2009, Hale et al., 2011, Lim & Harley, 2018). 

There is some evidence that polychaete sperm may be affected by ocean acidification at levels expected in the high emission scenario (pH 7.8), with percentage sperm motility (Schlegel et al., 2014) and sperm velocity (Campbell et al., 2014, Schlegel et al., 2014) decreasing in the polychaetes Galeolaria caespitosa and Arenicola marina, leading to a decrease in sperm fertility success (Campbell et al., 2014). While this may lead to some changes in species abundance, at natural CO₂ vents, the abundance of polychaetes either remained the same (Kroeker et al., 2011) or increased (Garrard et al., 2014, Vizzini et al., 2017).

Sensitivity assessment. No direct evidence of the impact of ocean acidification on Nephtys cirrosa or the amphipods and isopods that characterize this biotope was found, non-calcifying polychaetes and amphipods appear to be tolerant of increased pCO₂ and decreased pH in the vicinity of natural CO₂ seeps.  Therefore it is likely that the characterizing species of this biotope will show high resistance to a decrease in pH, although it must be noted that many species show variation in their response to pCO₂ independent of their taxonomic group or habitat preferences (Widdicombe & Spicer, 2008; Kroeker et al., 2013).

Nevertheless, the fauna are transient or opportunistic species washed in and out of the biotope by wave action, are highly mobile and/or capable of rapid reproduction and, while the relative abundance of different amphipods and isopods may change, the characteristic biotope will probably remain the same.  Hence, resistance to an increase in pCO₂ and decrease in pH under the middle, and high emission scenarios is assessed as 'High' and resilience as ‘High’ (by default) and this biotope is assessed as 'Not sensitive'.

Ocean acidification (middle)

Middle emission scenario benchmark: a further decrease in pH of 0.15 (annual mean) and corresponding 35% increase in H+ ions with no coastal aragonite undersaturation and the aragonite saturation horizon in the NE Atlantic, off the continental shelf, at a depth of 800 m by the end of this century 2081-2100. Further detail.

Evidence

There is no direct evidence of the impact of ocean acidification on either Nephtys cirrosa or the amphipods and isopods that characterize this habitat. Amphipods are generally thought to be less sensitive to ocean acidification than other taxa and are actually found in greater numbers at naturally CO₂ enriched vents (Kroeker et al., 2011, Garrard et al., 2014, Vizzini et al., 2017). Much of this increase in abundance is not expected to be directly related to CO₂ enrichment but rather due to indirect effects such as reduced predation or increased food supply (Kroeker et al., 2011; Kroeker et al., 2013, Garrard et al., 2014). A laboratory study found that under identical conditions other than CO₂ enrichment, the population size of the amphipod Gammarus locusta increased 20 fold and the proportion of gravid females doubled, suggesting that ocean acidification may confer an advantage to amphipods by relaxing environmental constraints on reproduction (Heldt et al., 2016). Kroeker et al. (2011) also noted no significant decrease in isopod abundance in areas of naturally low pH of 7.8 or 6.6.  However, while Garrard et al. (2014) noted no significant decrease in isopod abundance, isopod species richness was significantly decreased at pH 7.8.  Further laboratory experiments show little effect of ocean acidification on amphipods at levels expected for the high emission scenario at the end of this century (pH 7.8) (Hauton et al., 2009, Hale et al., 2011, Lim & Harley, 2018). 

There is some evidence that polychaete sperm may be affected by ocean acidification at levels expected in the high emission scenario (pH 7.8), with percentage sperm motility (Schlegel et al., 2014) and sperm velocity (Campbell et al., 2014, Schlegel et al., 2014) decreasing in the polychaetes Galeolaria caespitosa and Arenicola marina, leading to a decrease in sperm fertility success (Campbell et al., 2014). While this may lead to some changes in species abundance, at natural CO₂ vents, the abundance of polychaetes either remained the same (Kroeker et al., 2011) or increased (Garrard et al., 2014, Vizzini et al., 2017).

Sensitivity assessment. No direct evidence of the impact of ocean acidification on Nephtys cirrosa or the amphipods and isopods that characterize this biotope was found, non-calcifying polychaetes and amphipods appear to be tolerant of increased pCO₂ and decreased pH in the vicinity of natural CO₂ seeps.  Therefore it is likely that the characterizing species of this biotope will show high resistance to a decrease in pH, although it must be noted that many species show variation in their response to pCO₂ independent of their taxonomic group or habitat preferences (Widdicombe & Spicer, 2008; Kroeker et al., 2013).

Nevertheless, the fauna are transient or opportunistic species washed in and out of the biotope by wave action, are highly mobile and/or capable of rapid reproduction and, while the relative abundance of different amphipods and isopods may change, the characteristic biotope will probably remain the same.  Hence, resistance to an increase in pCO₂ and decrease in pH under the middle, and high emission scenarios is assessed as 'High' and resilience as ‘High’ (by default) and this biotope is assessed as 'Not sensitive'.

Sea level rise (extreme)

Extreme scenario benchmark: a 107 cm rise in average UK by the end of this century (2018-2100). Further detail.

Evidence

A rise in sea level increases the water depth at the shore and results in increased wave and tidal energy along the shore, due to the increase in fetch and reduction in wave attenuation (Pethick, 2001; Crooks, 2004; Fujii, 2012).  As a result, coast landforms (e.g. subtidal bedforms, intertidal flats, saltmarshes, shingle banks, sand dunes, cliffs and coastal lowlands) migrate along and parallel to the shore to maintain their position with the coastal energy gradient (Cooks, 2004; Fujii, 2012).  For example, mudflats migrate landwards to a lower energy position and may be replaced by sand flats that have themselves migrated landwards from exposed conditions (Crooks, 2004).  In effect, ‘coastal roll-over’ results as the shore moves landwards by the erosion of the landward, upper limit, of the shore and deposition at its lower limit (Crooks, 2004).  Pethick (2001) suggested that a sea-level rise rate of 6 mm/yr could result in landward movement of estuaries by 10 m/yr, long-shore migration of open coast landforms of 50 m/yr and ebb-tidal deltas to extend laterally by 300 m/yr. 

The effects of sea-level rise and increased wave action may be increase further due to storms and storms surges.  IPCC (2019) note that the frequency of extreme sea-level events (e.g. due to storms) are predicted to increase as sea-level rises, however there is no consensus on the future storm and, hence, wave climate around UK coasts (Mossman et al., 2015; Lowe et al., 2018; Palmer et al., 2018).

Sensitivity assessment.  This is a physical habitat dominated by medium to fine sand in a high energy environment, where the sand is mobilized by wave action or tidal water flow, or a mixture of both depending on location (JNCC, 2015).  It is recorded from 0 –20 m in depth.  The evidence suggests that sea-level rise could alter the hydrography and wave climate experienced by the habitat.  Wave action is reduced with increasing depth; therefore, sea-level rise may reduce the effect of wave action in the deeper examples or deeper reaches of this biotope.  Hence, where wave

exposure is the dominant factor structuring the biotope, the sediment may become more stable and the biotope transition into a more stable biotope with higher species richness, e.g. IFiSa.NcirBat.  As a result, part of the biotope might be lost.  However, the redistribution of sediments and change in hydrography may allow the biotope to extend inshore, depending on location.

There is likely to be considerable variation between sites, the relative contribution of wave action and water flow to sediment mobility, and the depth range occupied by the biotope.  Hence, it is difficult to assess the effect of the different sea-level rise scenarios.  As the biotope can occur from 0-20 m in depth, it is assumed that a sea-level rise of 50 cm, or 70 cm (middle to high emission scenarios) would have limited effect but that a 107 cm rise (the extreme scenario) might result in loss of part of the deeper extent of the biotope in some sites.  Therefore, resistance is assessed as ‘High’ under the middle and high emission scenarios so that resilience is ‘High’ and sensitivity assessed as ‘Not sensitive’.  But resistance is possibly ‘Medium’ under the extreme scenario, so that resilience is ‘Very low’ and sensitivity assessed as ‘Medium’, albeit with ‘Low’ confidence.

Sea level rise (high)

High emission scenario benchmark: a 70 cm rise in average UK by the end of this century (2018-2100). Further detail.

Evidence

A rise in sea level increases the water depth at the shore and results in increased wave and tidal energy along the shore, due to the increase in fetch and reduction in wave attenuation (Pethick, 2001; Crooks, 2004; Fujii, 2012).  As a result, coast landforms (e.g. subtidal bedforms, intertidal flats, saltmarshes, shingle banks, sand dunes, cliffs and coastal lowlands) migrate along and parallel to the shore to maintain their position with the coastal energy gradient (Cooks, 2004; Fujii, 2012).  For example, mudflats migrate landwards to a lower energy position and may be replaced by sand flats that have themselves migrated landwards from exposed conditions (Crooks, 2004).  In effect, ‘coastal roll-over’ results as the shore moves landwards by the erosion of the landward, upper limit, of the shore and deposition at its lower limit (Crooks, 2004).  Pethick (2001) suggested that a sea-level rise rate of 6 mm/yr could result in landward movement of estuaries by 10 m/yr, long-shore migration of open coast landforms of 50 m/yr and ebb-tidal deltas to extend laterally by 300 m/yr. 

The effects of sea-level rise and increased wave action may be increase further due to storms and storms surges.  IPCC (2019) note that the frequency of extreme sea-level events (e.g. due to storms) are predicted to increase as sea-level rises, however there is no consensus on the future storm and, hence, wave climate around UK coasts (Mossman et al., 2015; Lowe et al., 2018; Palmer et al., 2018).

Sensitivity assessment.  This is a physical habitat dominated by medium to fine sand in a high energy environment, where the sand is mobilized by wave action or tidal water flow, or a mixture of both depending on location (JNCC, 2015).  It is recorded from 0 –20 m in depth.  The evidence suggests that sea-level rise could alter the hydrography and wave climate experienced by the habitat.  Wave action is reduced with increasing depth; therefore, sea-level rise may reduce the effect of wave action in the deeper examples or deeper reaches of this biotope.  Hence, where wave

exposure is the dominant factor structuring the biotope, the sediment may become more stable and the biotope transition into a more stable biotope with higher species richness, e.g. IFiSa.NcirBat.  As a result, part of the biotope might be lost.  However, the redistribution of sediments and change in hydrography may allow the biotope to extend inshore, depending on location.

There is likely to be considerable variation between sites, the relative contribution of wave action and water flow to sediment mobility, and the depth range occupied by the biotope.  Hence, it is difficult to assess the effect of the different sea-level rise scenarios.  As the biotope can occur from 0-20 m in depth, it is assumed that a sea-level rise of 50 cm, or 70 cm (middle to high emission scenarios) would have limited effect but that a 107 cm rise (the extreme scenario) might result in loss of part of the deeper extent of the biotope in some sites.  Therefore, resistance is assessed as ‘High’ under the middle and high emission scenarios so that resilience is ‘High’ and sensitivity assessed as ‘Not sensitive’.  But resistance is possibly ‘Medium’ under the extreme scenario, so that resilience is ‘Very low’ and sensitivity assessed as ‘Medium’, albeit with ‘Low’ confidence.

Sea level rise (middle)

Middle emission scenario benchmark: a 50 cm rise in average UK sea-level rise by the end of this century (2081-2100). Further detail.

Evidence

A rise in sea level increases the water depth at the shore and results in increased wave and tidal energy along the shore, due to the increase in fetch and reduction in wave attenuation (Pethick, 2001; Crooks, 2004; Fujii, 2012).  As a result, coast landforms (e.g. subtidal bedforms, intertidal flats, saltmarshes, shingle banks, sand dunes, cliffs and coastal lowlands) migrate along and parallel to the shore to maintain their position with the coastal energy gradient (Cooks, 2004; Fujii, 2012).  For example, mudflats migrate landwards to a lower energy position and may be replaced by sand flats that have themselves migrated landwards from exposed conditions (Crooks, 2004).  In effect, ‘coastal roll-over’ results as the shore moves landwards by the erosion of the landward, upper limit, of the shore and deposition at its lower limit (Crooks, 2004).  Pethick (2001) suggested that a sea-level rise rate of 6 mm/yr could result in landward movement of estuaries by 10 m/yr, long-shore migration of open coast landforms of 50 m/yr and ebb-tidal deltas to extend laterally by 300 m/yr. 

The effects of sea-level rise and increased wave action may be increase further due to storms and storms surges.  IPCC (2019) note that the frequency of extreme sea-level events (e.g. due to storms) are predicted to increase as sea-level rises, however there is no consensus on the future storm and, hence, wave climate around UK coasts (Mossman et al., 2015; Lowe et al., 2018; Palmer et al., 2018).

Sensitivity assessment.  This is a physical habitat dominated by medium to fine sand in a high energy environment, where the sand is mobilized by wave action or tidal water flow, or a mixture of both depending on location (JNCC, 2015).  It is recorded from 0 –20 m in depth.  The evidence suggests that sea-level rise could alter the hydrography and wave climate experienced by the habitat.  Wave action is reduced with increasing depth; therefore, sea-level rise may reduce the effect of wave action in the deeper examples or deeper reaches of this biotope.  Hence, where wave

exposure is the dominant factor structuring the biotope, the sediment may become more stable and the biotope transition into a more stable biotope with higher species richness, e.g. IFiSa.NcirBat.  As a result, part of the biotope might be lost.  However, the redistribution of sediments and change in hydrography may allow the biotope to extend inshore, depending on location.

There is likely to be considerable variation between sites, the relative contribution of wave action and water flow to sediment mobility, and the depth range occupied by the biotope.  Hence, it is difficult to assess the effect of the different sea-level rise scenarios.  As the biotope can occur from 0-20 m in depth, it is assumed that a sea-level rise of 50 cm, or 70 cm (middle to high emission scenarios) would have limited effect but that a 107 cm rise (the extreme scenario) might result in loss of part of the deeper extent of the biotope in some sites.  Therefore, resistance is assessed as ‘High’ under the middle and high emission scenarios so that resilience is ‘High’ and sensitivity assessed as ‘Not sensitive’.  But resistance is possibly ‘Medium’ under the extreme scenario, so that resilience is ‘Very low’ and sensitivity assessed as ‘Medium’, albeit with ‘Low’ confidence.

Temperature increase (local)

Benchmark. A 5°C increase in temperature for one month, or 2°C for one year. Further detail

Evidence

The amphipods and isopods that occur within this habitat are mobile and can avoid unfavourable conditions to some extent. The isopod Eurydice pulchra, was observed to migrate seasonally off-shore in the Dovey Estuary (Wales). Bathyporeia life cycles vary between locations and this is related to temperature (Mettam, 1989). Preece (1971) tested temperature tolerances of Bathyporeia pelagica and Bathyporeia pilosa in the laboratory.  Individuals acclimated to 15°C for 24 hours were exposed to temperature increases (water temperature raised by 0.2^oC/minute). As test  temperature were reached individuals were removed, placed in seawater at 4°C and allowed to recover for 24 hours at which point mortalities were tested. Amphipods were also allowed to bury into sediments and held at test temperatures for 24 hours of 32.5°C, 31.8°C and 29.5°C before being allowed to recover in fresh seawater at 15°C for a further 24 hours, before mortalities were assessed. Upper lethal temperatures (the temperature at which 50% of individuals died for adult males and gravid females of Bathyporeia pilosa were 37.5°C and 39.4°C respectively. Bathyporeia pelagica exhibited lower tolerances and adult males and gravid females had upper lethal temperature tolerances of 33.4 and 34.2°C respectively. These tests measures short-term exposure only and species had lower tolerance for longer-term (24 hour exposure).  No mortality occurred for Bathyporeia pilosa individuals held at 29.5^oC and 30.8^oC; however 15% of individuals exposed to water temperatures of 31.8°C and 96% at 32.5°C died. Bathyporeia pelagica exhibited lower tolerances, 11% of individuals died after 24 hr exposure to 29.5^oC and 100% mortality occurred at 30.8^oC and above (Preece, 1971).

Emery et al. (1957) reported that Nephtys spp. could withstand summer temperatures of 30-35°C so is likely to withstand the benchmark acute temperature increase. An acute increase in temperature at the benchmark level may result in physiological stress endured by the infaunal species but is unlikely to lead to mortality.

Sensitivity assessment. Typical surface water temperatures around the UK coast vary seasonally from 4-19°C (Huthnance, 2010).  A chronic increase in temperature throughout the year of 2°C may fall within the normal temperature variation and an acute increase in water temperatures from 19 to 24°C for a month may be tolerated by the characterizing species supported by deeper burrowing and/or migration. For Bathyporeia spp. temperature increases above 30°C appear to be critical based on Preece (1971). Biotope resistance is therefore assessed as ‘High’ and resilience as ‘High’ so that the biotope is assessed as ‘Not sensitive’. Increased water and air temperatures and desiccation may lead to greater synergistic effects and the loss of characterizing amphipods and isopods may result in shifts between the variant sub-biotopes. 

Temperature decrease (local)

Benchmark. A 5°C decrease in temperature for one month, or 2°C for one year. Further detail

Evidence

Crisp (1964) reported that species of amphipod and isopods seemed to be unharmed by the severe winter of 1962-1963. This may be due to burial in sediments buffering temperature or seasonal migration to deeper waters to avoid freezing.  In the winter, Eurydice pulchra , for example, migrates from the intertidal into the sublittoral zone, thus escaping extreme temperatures (Jones, 1970b) and winter migrations have also been observed for Bathyporeia spp. (Fish & Fish, 1978; Fish & Preece, 1970).

Preece (1971) tested the temperature tolerances of Bathyporeia pelagica and Bathyporeia pilosa in the laboratory.  Individuals acclimated to 15^oC for 24 hours were placed in a freezer in wet sediment. As test temperatures were reached individuals were removed and allowed to recover for 24 hours at which point mortalities were tested. Amphipods were also allowed to bury into sediments and held at test temperatures of -1^oc, -3^oC and -5^oC for 24 hours before being allowed to recover in fresh seawater at 15^oC for a further 24 hours before mortalities were assessed. Lower lethal short-term tolerances of Bathyporeia pilosa and Bathyporeia pelagica were -13.6^oC and -6.4^oC respectively.  Sensitivity to longer-term exposure is greater, especially for Bathyporeia pelagica. Bathyporeia pilosa individuals could withstand temperatures as low as -1^oC for 24 hours, while 42% of Bathyporeia pelagica died. At -3^oC 5% of Bathyporeia pilosa died (100% of Bathyporeia pelagica) but this rose to 82% at -5^oC.

Nephtys cirrosa reaches its northern limit in Scotland, and German Bight of the North Sea. A decrease in temperature is likely to result in loss of the species from the SS.SSa.SSaVS biotope in Scotland.

Sensitivity assessment. Typical surface water temperatures around the UK coast vary seasonally from 4-19 ^oC (Huthnance, 2010).  A chronic decrease in temperature throughout the year of 2^oC may fall within the normal temperature variation but an acute decrease in water temperatures from 4^oC to -1^oC at the coldest part of the year may lead to freezing and lethal effects on for a month may be tolerated by the characterizing species supported by deeper burrowing and/or migration to deeper waters. For Bathyporeia spp. seawater temperature decreases below -1^oC appear to be critical based on Preece (1971). Biotope resistance is therefore assessed as ‘Medium’ and resilience as ‘High’ so that biotope sensitivity is assessed as 'Low'.

Salinity increase (local)

Benchmark. A increase in one MNCR salinity category above the usual range of the biotope or habitat. Further detail

Evidence

This biotope is found in full salinity (30-35 ppt) habitats (JNCC, 2015), a change at the pressure benchmark is therefore assessed as a change to hypersaline conditions. Little evidence was found to assess responses to hypersalinity. However, monitoring at a Spanish desalination facility where discharges close to the outfall reached a salinity of 53, found that amphipods were sensitive to the increased salinity and that species free-living in the sediment were most sensitive. The study area did not host any of the species characterizing this biotope but the results indicate a general sensitivity (De-la-Ossa-Carretero, et al., 2016).

Sensitivity assessment.  Not assessed, ‘No evidence’.

Salinity decrease (local)

Benchmark. A decrease in one MNCR salinity category above the usual range of the biotope or habitat. Further detail

Evidence

The biotope is found in full salinity habitats (JNCC, 2015). A change at the pressure benchmark refers to a decrease from full to variable (18-35 ppt), or to reduced salinity (18-30 ppt). Eurydice pulchra was found to be relatively euryhaline (Jones, 1970b), whilst Bathyporeia pelagica migrates seaward in response to reduced salinities, the effect of which is enhanced by higher temperature (Preece, 1970). Bathyporeia pilosa is, however, more tolerant of low salinities and is capable of reproducing at salinities as low as 2 (Khayrallah, 1977). Populations of Bathyporeia pilosa within the upper reaches of the Severn Estuary experience wide fluctuations in salinity ranging from 1-22 depending on the season and tidal cycle (Mettam, 1989). The physiological stress for this environment affects size and reproduction (Mettam, 1989). Speybroeck et al. (2008) noted that Bathyporeia pilosa tends to occur subtidally in estuarine and brackish conditions. Local populations may be acclimated to the prevailing salinity regime and may exhibit different tolerances to other populations subject to different salinity conditions and, therefore, caution should be used when inferring tolerances from populations in different regions.  

A reduction in salinity at the pressure benchmark is likely to result in the loss of species and biotope reversion to the biotope SS.SSa.SSaVS.MoSaVS, which occurs in typical mobile sand conditions but in reduced salinities and lacks Nepthys cirrosa and Bathyporeia spp. (although these may be washed in from adjacent communities) (JNCC, 2015).

Sensitivity assessment. A decrease in salinity is likely to lead to changes in species abundance and richness and biotope reclassification to SS.SSa.SSaVS.MoSaVS. Biotope resistance is assessed as ‘None’ and resilience as ‘High’ (following restoration of typical habitat conditions). Sensitivity is therefore assessed as ‘Medium’. 

Water flow (tidal current) changes (local)

Benchmark. A change in peak mean spring bed flow velocity of between 0.1 m/s to 0.2 m/s for more than one year. Further detail

Evidence

Water movement is a key factor physically structuring this biotope, with sediment sorting and mobilisation by tidal streams and wave action modifying the sediments present and the level of disturbance. This biotope is recorded where tidal streams may be strong (1.5-3 m/s) or very weak (negligible) (JNCC, 2015), in areas where flows are lower, wave action may be more important in maintaining the sediment mobility that structures the biotope.  Where similar sand habitats occur in  more sheltered areas the biological structure alters in response to the decrease in sediment mobility and the biotope SS.SSa.IFiSa.NcirBat may develop. 

Sensitivity assessment. The sediments that characterize this biotope and sub-biotopes are mobile sands that range from medium to fine, a change at the pressure benchmark (increase or decrease) may lead to some changes in sediment sorting. Based on the range of water flows experienced, biotopes occurring in habitats at the middle of the range are considered to be 'Not sensitive' to an increase or decrease in flow at the pressure benchmark. Changes in water flow in areas sheltered from wave action could. however, lead to changes in biotope classification due to the increase in sediment stability.

Emergence regime changes

Benchmark.  1) A change in the time covered or not covered by the sea for a period of ≥1 year or 2) an increase in relative sea level or decrease in high water level for ≥1 year. Further detail

Evidence

Not relevant to sublittoral biotopes.​

Wave exposure changes (local)

Benchmark. A change in near shore significant wave height of >3% but <5% for more than one year. Further detail

Evidence

Water movement is a key factor physically structuring this biotope, with sediment sorting and mobilisation by tidal streams and wave action modifying the sediments present and the level of disturbance. The assessed biotope is found in habitats that are exposed to sheltered from wave action (JNCC, 2015).

Sensitivity assessment. Wave action is a key factor structuring this biotope through sediment mobility.  As the biotope occurs across three wave exposure categories (JNCC, 2015) this is considered to indicate, by proxy, that a change in wave exposure at the pressure benchmark is less than the natural range of wave heights experienced.  Biotope resistance to this pressure is therefore assessed as ‘High’ and resilience as ‘High (by default) so that the biotope is considered to be ‘Not sensitive’ at the pressure benchmark. 

Transition elements & organo-metal contamination

Benchmark. Exposure of marine species or habitat to one or more relevant contaminants via uncontrolled releases or incidental spills. Further detail

Evidence

This pressure is Not assessed but evidence is presented where available.

Levels of contaminants that exceed the pressure benchmark may cause impacts. For most metals, toxicity to crustaceans increases with decreased salinity and elevated temperature, therefore marine species living within their normal salinity range may be less susceptible to heavy metal pollution than those living in salinities near the lower limit of their salinity tolerance (McLusky et al., 1986). Jones (1973; 1975b) found that mercury (Hg) and copper (Cu) reacted synergistically with changes in salinity and increased temperature (10°C) to become increasingly toxic to species of isopod, including Eurydice pulchra.

Hydrocarbon & PAH contamination

Benchmark. Exposure of marine species or habitat to one or more relevant contaminants via uncontrolled releases or incidental spills. Further detail

Evidence

This pressure is Not assessed but evidence is presented where available.

Synthetic compound contamination

Benchmark. Exposure of marine species or habitat to one or more relevant contaminants via uncontrolled releases or incidental spills. Further detail

Evidence

This pressure is Not assessed but evidence is presented where available.

In general, crustaceans are widely reported to be intolerant of synthetic chemicals (Cole et al., 1999) and intolerance to some specific chemicals has been observed in amphipods. Powell (1979) inferred from the known susceptibility of Crustacea to synthetic chemicals and other non-lethal effects, that there would probably also be a deleterious effect on isopod fauna as a direct result of chemical application. Toxicity tests conducted by Smith (1968), indicated that survival of Eurydice pulchra after oil detergent treatment was above average for crustaceans. All were killed at about 10 ppm BP 1002 after 24 hours exposure, whilst at 5 ppm four out of five individuals survived when transferred to clean seawater. However, in the field a proportion of the Eurydice pulchra population survived exposure to lethal concentrations of BP 1002, both in the sand and water.

Radionuclide contamination

Benchmark. An increase in 10µGy/h above background levels. Further detail

Evidence

No evidence.

Introduction of other substances

Benchmark. Exposure of marine species or habitat to one or more relevant contaminants via uncontrolled releases or incidental spills. Further detail

Evidence

This pressure is Not assessed.

De-oxygenation

Benchmark. Exposure to dissolved oxygen concentration of less than or equal to 2 mg/l for one week (a change from WFD poor status to bad status). Further detail

Evidence

Information concerning the reduced oxygen tolerance of Nephtys cirrosa was not found but evidence (Alheit, 1978; Arndt & Schiedek, 1997; Fallesen & Jørgensen, 1991) indicated a similar species, Nephtys hombergii, to be very tolerant of episodic oxygen deficiency and at the benchmark duration of one week.

Laboratory studies by Khayrallah (1977) on Bathyporeia pilosa, indicated that it has a relatively poor resistance to conditions of hypoxia in comparison to other interstitial animals. However, Mettam (1989) and Sandberg (1997) suggest that Bathyporeia pilosa can survive short-term hypoxia.

Sensitivity assessment.  This biotope  is characterized by mobile sands in areas that experience strong water flows or are wave exposed. The mixing effect of wave action and water movement will limit the intensity and duration of exposure to deoxygenated waters. The species characterizing the biotope are also mobile and able to migrate vertically or shorewards to escape unsuitable conditions. Biotope resistance is therefore assessed as ‘High’ and resilience as ‘High’ (by default) so that the biotope is considered to be ‘Not sensitive’.

Nutrient enrichment

Benchmark. Compliance with WFD criteria for good status. Further detail

Evidence

In-situ primary production is limited to microphytobenthos within and on sediments and the high levels of sediment mobility may limit the level of primary production as abrasion would be likely to damage diatoms (Delgado et al., 1991). The amphipods feed on epipsammic diatoms attached to the sand grains (Nicolaisen & Kanneworff, 1969). Both these groups may benefit from slight nutrient enrichment if this enhanced primary production. 

Sensitivity assessment.  Nutrient level is not a key factor structuring the biotope at the pressure benchmark. In general, however, primary production is low and this biotope is species poor and characterizing species may be present at low abundances (depending on sediment mobility). Biotope resistance is therefore assessed as ‘High’, resilience as ‘High’ (by default) and the biotope is considered to be ‘Not sensitive’.

Organic enrichment

Benchmark. A deposit of 100 gC/m²/yr. Further detail

Evidence

The biotope occurs in mobile sand sediments where wave action leads to particle sorting, in-situ primary production is restricted to microphytobenthos although sediment mobility may restrict production levels (Delgado et al., 1991). 

Sensitivity assessment.  At the pressure benchmark organic inputs are unlikely to significantly affect the structure of the biological assemblage or impact the physical habitat, due to remobilisation and transport by wave or currents. Biotope sensitivity is therefore assessed as ‘High’ and resilience as ‘High’ (by default) and the biotope is therefore considered to be ‘Not sensitive’.

Physical loss (to land or freshwater habitat)

Benchmark. A permanent loss of existing saline habitat within the site. Further detail

Evidence

All marine habitats and benthic species are considered to have a resistance of ‘None’ to this pressure and to be unable to recover from a permanent loss of habitat (resilience is ‘Very Low’).  Sensitivity within the direct spatial footprint of this pressure is therefore ‘High’.  Although no specific evidence is described confidence in this assessment is ‘High’, due to the incontrovertible nature of this pressure.

Physical change (to another seabed type)

Benchmark. Permanent change from sedimentary or soft rock substrata to hard rock or artificial substrata or vice-versa. Further detail

Evidence

The biotope is characterized by the sedimentary habitat (JNCC, 2015), a change to an artificial or rock substratum would alter the character of the biotope leading to reclassification and the loss of the sedimentary community including the characterizing polychaetes, amphipods and isopods.

Sensitivity assessment. Based on the loss of the biotope, resistance is assessed as ‘None’, recovery is assessed as ‘Very low’ (as the change at the pressure benchmark is permanent and sensitivity is assessed as ‘High’.

Physical change (to another sediment type)

Benchmark. Permanent change in one Folk class (based on UK SeaMap simplified classification). Further detail

Evidence

The pressure benchmark refers to the simplified Folk classification developed by Long (2006) and the UK Marine Habitat Classification Littoral and Sublittoral Sediment Matrices (Connor et al., 2004). The biotope occurs on mobile sands, a change at the pressure benchmark refers to a change to sandy muds or muddy sands or to coarser gravel sediments. Experiments by Van Tomme et al. (2013) have shown that the optimal sedimentary habitats for some of he species that characterize this biotope vary slightly. Bathyporeia pilosa and Eurydice pulchra prefer the finest sediments, although at a subtidal dredge disposal site the change to a finer sediment led to a reduction in the abundance of Bathyporeia pilosa (Witt et al., 2004). Bathyporeia sarsi has a broader preference and also occurred in medium-coarse sediments (Van Tomme et al., 2013). 

Nepthys cirrosa occurs in fine to coarser sands, with greatest abundance in the Belgium part of the North Sea recorded in medium grain sizes (Degraer et al., 2006). A change to gravelly sand is unlikely to impact this species, however, a change to muddy sand may limit the species abundance as the species displays a slight preference for low mud content levels (< 10%) (Degraer et al., 2006).  

Sensitivity assessment. A change to either a finer muddy sediment or a coarser sediment, is likely to lead to changes in the abundance and identity of the characterizing species . Based on the loss of the biotope, resistance is assessed as ‘None’, recovery is assessed as ‘Very low’ (as the change at the pressure benchmark is permanent and sensitivity is assessed as ‘High’.

Habitat structure changes - removal of substratum (extraction)

Benchmark. The extraction of substratum to 30 cm (where substratum includes sediments and soft rock but excludes hard bedrock). Further detail

Evidence

Bathyporeia pelagica lives infaunally in the uppermost 3 cm of sandy substrata as does the isopod Eurydice pulchra (Fish, 1970). Extraction of the sediment to 30cm is likely to remove the characterizing polychaetes, amphipods and isopods within the footprint (although if disturbed some may be able to escape). 

Sensitivity assessment. Biotope resistance to extraction of sediment and characterizing species is assessed as ‘None. Resilience is assessed as ‘High’, as sediment recovery will be enhanced by wave action and mobility of sand. The characterizing species are likely to recover through transport of adults in the water column or migration from adjacent patches. Biotope sensitivity is therefore assessed as ‘Medium’.

Abrasion / disturbance of the surface of the substratum or seabed

Benchmark. Damage to surface features (e.g. species and physical structures within the habitat). Further detail

Evidence

This biotope group is present in mobile sands, the associated species are generally present in low abundances and adapted to frequent disturbance suggesting that resistance to surface abrasion would be high. The amphipod and isopod species present are agile swimmers and are characterized by their ability to withstand sediment disturbance (Elliott et al. 1998). Similarly, the polychaete Nephtys cirrosa is adapted to life in unstable sediments and lives within the sediment. This characteristic is likely to protect this species from surface abrasion.

Comparisons between shores with low and high levels of trampling found that the amphipod Bathyporeia pelagica is sensitive to abrasion and compaction from human trampling, other species including Pontocrates arenarius and the isopod Eurydice affinis also decreased in response to trampling but Bathyporeia pelagica appeared to be the most sensitive  (Reyes-Martínez et al., 2015).  

Sensitivity assessment. Resistance to a single abrasion event is assessed as ‘Low’ based on the evidence for trampling from Reyes-Martínez et al. (2015). Resilience is assessed as ‘High’, based on migration from adjacent populations and in-situ reproduction by surviving amphipods.  Sensitivity is therefore assessed as ‘Low’. This assessment may underestimate sensitivity to high-levels of abrasion (repeated events within a short period). The trampling evidence and the evidence for penetration from mobile gears (see below) differ in the severity (resistance) of impact. This may be due to different levels of intensity (multiple trampling/abrasion events vs single penetration/towed gear impacts) or the nature of the pressure. Abrasion from trampling also involves a level of compaction that could collapse burrows and damage species through compression. Penetration may, however, break sediments open allowing mobile species to escape or species may be pushed forwards from towed gear by a pressure wave where this is deployed subtidally (Gilkinson et al., 1998). Both risk assessments are considered applicable to single events based on the evidence and the sensitivity assessment for both pressures is the same although resistance differs. 

Penetration or disturbance of the substratum subsurface

Benchmark. Damage to sub-surface features (e.g. species and physical structures within the habitat). Further detail

Evidence

This biotope group is present in mobile sands, the associated species are generally present in low abundances and adapted to frequent disturbance suggesting that resistance to abrasion and penetration and disturbance of the sediment would be high. The amphipod and isopod species present are agile swimmers and are characterized by their ability to withstand sediment disturbance (Elliott et al. 1998).

Bergman and Santbrink (2000) found that direct mortality of gammarid amphipods, following a single passage of a beam trawl (in silty sediments where penetration is greater) was 28%. Similar results were reported from experiments in shallow, wave disturbed areas, using a toothed, clam dredge. Bathyporeia spp. experienced a reduction of 25% abundance in samples immediately after intense clam dredging, abundance recovered after 1 day (Constantino et al. 2009). Experimental hydraulic dredging for razor clams resulted in  no statistically significant differences in Bathyporeia elegans abundances between treatments after 1 or 40 days (Hall et al., 1990), suggesting that recovery from effects was very rapid. Ferns et al. (2000) examined the effects of a tractor-towed cockle harvester on benthic invertebrates and predators in intertidal plots of muddy and clean sand. Harvesting resulted in the loss of a significant proportion of the most common invertebrates from both areas. In the muddy sand, the population of Bathyporeia pilosa remained significantly depleted for more than 50 days, whilst the population in clean sand recovered more quickly. These results agree with other experimental studies that clean sands tend to recover more quickly that other habitat types with higher proportions of fine sediment (Dernie et al., 2003).

Sensitivity assessment. Based on the evidence above it is considered that Bathyporeia spp. and other characterizing species will have ‘Medium’ resistance (mortality <25%) to abrasion, their small size, infaunal position and mobility enabling a large proportion of the population to escape injury. Recovery is assessed as ‘High’ and sensitivity is therefore categorised as ‘Low’.The trampling evidence (see above) and the evidence for penetration from mobile gears  differ in the severity (resistance) of impact. This may be due to different levels of intensity (multiple trampling/abrasion events vs single penetration/towed gear impacts) or the nature of the pressure. Abrasion from trampling also involves a level of compaction that could collapse burrows and damage species through compression. Penetration may, however, break sediments open allowing mobile species to escape or species may be pushed forwards from towed gear by a pressure wave where this is deployed subtidally (Gilkinson et al., 1998). 

Changes in suspended solids (water clarity)

Benchmark. A change in one rank on the WFD (Water Framework Directive) scale e.g. from clear to intermediate for one year. Further detail

Evidence

The characterizing species live within the sand and are unlikely to be directly affected by an increased concentration of suspended matter in the water column. Within the mobile sands habitat storm events or spring tides may re-suspend or transport large amounts of material and therefore species are considered to be adapted to varying levels of suspended solids.

 Bathyporeia spp. feed on diatoms within the sand grains (Nicolaisen & Kanneworff, 1969), an increase in suspended solids that reduced light penetration could alter food supply. However, diatoms are able to photosynthesise while the tide is out and therefore a reduction in light during tidal inundation may not affect this food source , depending on the timing of the tidal cycle.  The isopod Eurydice pulchra feeds on the amphipod and polychaete characterizing species and, it may, therefore, be indirectly affected by changes in food supply if other species are impacted by changes in suspended solids. Nephtys cirrosa is also a carnivore.

Amphipods and isopods may be regular swimmers within the surf plankton, where the concentration of suspended particles would be expected to be higher (Fincham, 1970a). Furthermore, during the winter, when Bathyporeia pelagica extends its distribution into the mouths of estuaries the species may encounter concentrations of suspended sediment measurable in grams per litre (benchmark is mg/l) (Cole et al. 1999).  

Sensitivity assessment. Increased inorganic suspended solids may increase abrasion but it is likely that the infaunal species would be unaffected. The biotope is considered to be ‘Not sensitive’ to a decrease in suspended solids that does not affect sediment transport and supply to the biotope. Biotope resistance is assessed as ‘Medium’ as some effects on feeding and diatom productivity may occur from increases in suspended solids, resilience is assessed as ‘High’, following a return to usual conditions and sensitivity is assessed as ‘Low’. This more precautionary assessment is presented in the table.  Indirect effects such as deposition, erosion and associated sediment change that may result from changes in suspended solids in the long-term are assessed separately. 

Smothering and siltation rate changes (light)

Benchmark. ‘Light’ deposition of up to 5 cm of fine material added to the seabed in a single discrete event. Further detail

Evidence

Evidence for the effects of siltation by thick layers of added sediment from beach nourishment is described for the heavy deposition pressure below. The pressure benchmark for light deposition refers to the addition of a relatively thin layer of deposits in a single event.  Species adapted to coarse sediments may not be able to burrow through fine sediments, or experienced reduced burrowing ability. For example, Bijkerk (1988, results cited from Essink, 1999) found that the maximal overburden through which Bathyporeia could migrate was approximately 20 cm in mud and 40 cm in sand.  No further information was available on the rates of survivorship or the time taken to reach the surface.

Sensitivity assessment.  As the biotope is associated with wave exposed habitats or those with strong currents, some sediment removal will occur, mitigating the effect of deposition. The mobile polychaete Nephtys cirrosa, amphipods and the isopod Eurydice pulchra are likely to be able to burrow through a 5cm layer of fine sediments. Biotope resistance is therefore assessed as ‘High’ and resilience as ‘High’ (by default). The biotope is therefore considered to be ‘Not sensitive’ to this pressure.  Repeated deposits or deposits over a large area or in sheltered systems that were shifted by wave and tidal action may result in sediment change (see physical change pressure).

Smothering and siltation rate changes (heavy)

Benchmark. ‘Heavy’ deposition of up to 30 cm of fine material added to the seabed in a single discrete event. Further detail

Evidence

Studies have found that beach ‘replenishment’ or ‘nourishment’ that involves the addition of sediments on beaches can have a number of impacts on the infauna (Peterson et al., 2000, Peterson et al., 2006). Impacts are more severe when the sediment added differs significantly in grain size or organic content (Nelson et al., 1989, Peterson et al., 2000).  For example, Maurer et al. (1981) found that the amphipod Parahaustorius longimerus which occurs intertidally in clean, well-sorted sands and is an active, effective burrower was able to regain the surface after being buried by sand far more easily than when buried under silt/clay mixtures.

A thick layer of sediment has a smothering effect and in most instances buried species will die although some polychaetes can escape up to 90cm of burial In response to nourishment (Speybroek et al., 2007, references therein). Peterson et al. (2000) found that the dominant macrofauna were reduced by 86-99% 5-10 weeks after the addition of sediment that was finer than the original sediments but with a high shell content.

Little empirical information was found for the ability of characterizing species to reach the surface after burial. Bijkerk (1988, results cited from Essink, 1999) found that the maximal overburden through which Bathyporeia could migrate was approximately 20 cm in mud and 40 cm in sand.  No further information was available on the rates of survivorship or the time taken to reach the surface and no information was available for other characterizing species.

Leewis et al. (2012) investigated the recovery of Eurydice pulchra and Bathyporeia sarsi, following beach nourishment by comparing beaches that had been exposed at different times. The lengths of beach nourished varied from 0.5 kn to > 7 km.  Recovery to original abundances appeared to occur within one year for the characterizing species which were in agreement with other studies (Leewis et al., 2012 and references therein).  

Repeated events are not considered at the pressure benchmark but it is noted that annual beach nourishment can alter beach sediments (see physical change pressure) and result in suppression of macroinvertebrate populations (Manning et al., 2014).

Sensitivity assessment. The thickness of sediment applied during beach nourishment is likely to exceed the 30cm pressure benchmark but the results from studies on the activity are informative, particularly with regard to recovery rate. Sediment removal by wave action could mitigate the level of effect but overall smothering by fine sediments is likely to result in mortality of characterizing amphipods and isopods and possibly Nephtys cirrosa. Biotope resistance is therefore assessed as ‘Low’ and resilience as 'High' (based on Leewis et al., 2012), biotope sensitivity is therefore assessed as ‘Low’.

Litter

Benchmark. The introduction of man-made objects able to cause physical harm (surface, water column, seafloor or strandline). Further detail

Evidence

This pressure is not assessed. Amphipods may also consume microplastics although no negative effects have been documented. Ugolini et al. ( 2013) found that Talitrus saltator could consume polyethylene microspheres.  Most microspheres were expelled in 24 h. and were totally expelled in one week. microsphere ingestion on the survival capacity in the laboratory. Analyses carried out on faeces of freshly collected individuals revealed the presence of polyethylene and polypropylene, confirming that microplastic debris could be swallowed by Talitrus saltator in natural conditions. The talitrid Orchestia gammarellus has also been recorded as ingesting microplastics in the size range 20-200µm (Thompson et al., 2004).

Electromagnetic changes

Benchmark. A local electric field of 1 V/m or a local magnetic field of 10 µT. Further detail

Evidence

No evidence for the characterizing species was found to assess this pressure. For some amphipods there is evidence for geomagnetic orientation being inhibited or disrupted by the presence of electromagnetic fields or by changing magnetic fields. Arendse & Barendregt (1981) manipulated magnetic fields to alter orientation of the talitrid amphipod Orchestia cavimana. 

Deep-water amphipods Gondogenia arctica have been shown to be sensitive to even weak electromagnetic fields which cancel magnetic orientation (Tomanova & Vacha, 2016). Loss of orientation was observed at a radiofrequency electromagnetic field of 2 nT (0.002  µT) (Tomanova & Vacha, 2016).

Underwater noise changes

Benchmark. MSFD indicator levels (SEL or peak SPL) exceeded for 20% of days in a calendar year. Further detail

Evidence

Not relevant.

Introduction of light or shading

Benchmark. A change in incident light via anthropogenic means. Further detail

Evidence

As this feature is not characterized by the presence of primary producers it is not considered that shading would alter the character of the habitat. No specific evidence was found to assess the sensitivity of the characterizing species to this pressure. Changes in light level may, however, affect activity rhythms of the invertebrates. Amphipods within the biotope prefer shade and therefore an increase in light may inhibit activity, particularly at night when they emerge from the sediment and are most active (Jelassi et al., 2015; Ayari, 2015). Hartwick (1976) found that artificial lighting interfered with learning or orientation cues by Talitrids.  

Orientation by light has been well studied for intertidal amphipods (particularly Talitrus saltator). Intertidal amphipods orientate themselves by a range of factors that include (but are not limited to) visual cues based on solar or astronomic cues such as the moon and the geomagnetic field (Scapini, 2014). Activity patterns are also linked to internal biological clocks that respond to diel, tidal, lunar and seasonal cycles, so that animals are active during the most suitable time of day or night (Scapini, 2014).  The introduction of light or an increase in shading could, therefore, alter behavioural patterns and navigation.

Changes in light and level of shade may indirectly affect the characterizing Bathyporeia spp. through changes in  behaviour and food supply via photosynthesis of diatoms within sediments. Benthic microalgae play a significant role in system productivity and trophic dynamics, as well as habitat characteristics such as sediment stability (Tait & Dipper, 1998). Shading could prevent photosynthesis leading to death or migration of sediment diatoms altering sediment cohesion and food supply to the grazing amphipods.

Sensitivity assessment. Changes in light are not considered to directly affect the biotope however, some changes in behaviour or food supply for Bathyporeia spp could result. Sensitivity is assessed as ‘Medium’ and resilience is assessed as ’High’. Biotope sensitivity is, therefore, assessed as ‘Low’.

Barrier to species movement

Benchmark. A permanent or temporary barrier to species movement over ≥50% of water body width or a 10% change in tidal excursion. Further detail

Evidence

As the amphipods and isopods that characterize this biotope have benthic dispersal strategies (via brooding), water transport is not a key method of dispersal over wide distances, as it is for some marine invertebrates that produce pelagic larvae such as the characterizing Nephtys cirrosa.  Barriers that limit tidal excursion and flushing may reduce connectivity or help to retain larvae.

Sensitivity assessment. The biotope (based on the biological assemblage) is considered to have ‘High’ resistance to the presence of barriers that lead to a reduction in tidal excursion, resilience is assessed as ‘High’ (by default) and the biotope is considered to be ‘Not sensitive’.

Death or injury by collision

Benchmark. Injury or mortality from collisions of biota with both static or moving structures due to 0.1% of tidal volume on an average tide, passing through an artificial structure. Further detail

Evidence

Not relevant’ to seabed habitats.  NB. Collision by grounding vessels is addressed under ‘surface abrasion.

Visual disturbance

Benchmark. The daily duration of transient visual cues exceeds 10% of the period of site occupancy by the feature. Further detail

Evidence

The characterizing species are likely to be able to detect light and some movement but are unlikely to have any visual acuity and are considered to not be sensitive to this factor. The amphipods emerge from the sediments at night and are unlikely to be disturbed although like many species they may flee from movements.

Genetic modification & translocation of indigenous species

Benchmark. Translocation of indigenous species or the introduction of genetically modified or genetically different populations of indigenous species that may result in changes in the genetic structure of local populations, hybridization, or change in community structure. Further detail

Evidence

Key characterizing species within this biotope are not cultivated or translocated. This pressure is therefore considered ‘Not relevant’ to this biotope group.

Introduction or spread of invasive non-indigenous species

Benchmark. The introduction of one or more invasive non-indigenous species (INIS). Further detail

Evidence

The American slipper limpet Crepidula fornicata was introduced to the UK and Europe in the 1870s from the Atlantic coasts of North America with imports of the eastern oyster Crassostrea virginica. It was recorded in Liverpool in 1870 and the Essex coast in 1887-1890. It has spread through expansion and introductions along the full extent of the English Channel and into the European mainland (Blanchard, 1997, 2009; Bohn et al., 2012, 2013a, 2013b, 2015; De Montaudouin et al., 2018; Helmer et al., 2019; Hinz et al., 2011; McNeill et al., 2010; Powell-Jennings & Calloway, 2018; Preston et al., 2020; Stiger-Pouvreau & Thouzeau, 2015).

Crepidula fornicata is recorded from shallow, sheltered bays, lagoons and estuaries or the sheltered sides of islands, in variable salinity (18 to 40) although it prefers ca 30 (Tillin et al., 2020). Larvae require hard substrata for settlement. It prefers muddy gravelly, shell-rich, substrata that include gravel, or shells of other Crepidula, or other species e.g., oysters, and mussels. It is highly gregarious and seeks out adult shells for settlement, forming characteristic ‘stacks’ of adults. But it also recorded in a wide variety of habitats including clean sands, artificial substrata, Sabellaria alveolata reefs and areas subject to moderately strong tidal streams (Blanchard, 1997, 2009; Bohn et al., 2012, 2013a, 2013b, 2015; De Montaudouin et al., 2018; Hinz et al., 2011; Powell-Jennings & Calloway, 2018; Preston et al., 2020; Stiger-Pouvreau & Thouzeau, 2015; Tillin et al., 2020).

The availability of hard substrata (e.g., gravel) may only restrict initial colonization as higher densities of Crepidula function as substrata for subsequent colonization (Thieltges et al., 2004; Blanchard, 2009). However, Bohn et al. (2015) noted that Crepidula occurred at low density or was absent in areas of homogenous fine sediment and areas dominated by boulders. Bohn et al. (2015) suggested that wave action (exposure) probably prevented the establishment of large numbers of Crepidula in high-energy areas. Blanchard (2009) noted that sandy areas in the Bay of Saint-Mont Michel were not colonized by Crepidula because of surface sand mobility. Thieltges et al. (2003) also noted that storm events removed some clumps of mussels and presumably Crepidula onto tidal flats where they disappeared, which caused their abundance to fluctuate. Similarly, Crepidula was absent from sandy substrata in Swansea Bay but was most abundant in the shelter of the breakwater at the Swansea east site (Powell-Jennings & Calloway, 2018). Powell-Jennings & Calloway (2018) noted that Crepidula is killed by sudden burial and possibly burial due to deposition, which could mitigate Crepidula density.

The North American amphipod Gammarus tigrinus was detected in the north-eastern Baltic Sea in 2003 and has rapidly expanded into European waters since (Jänes et al., 2015). Native gammarids, such as Gammarus salinus have almost disappeared from some habitats of the northeastern Baltic Sea and the competition for space between the invasive Gammarus tigrinus and the native Gammarus salinus has been a contributing factor in certain habitats (Kotta et al., 2011). Competition for space alone did not explain the mass disappearance of Gammarus salinus as Gammarus tigrinus did not out-compete Gammarus salinus in all Baltic Sea habitats, limiting confidence in the evidence. However, Gammarus tigrinus has been identified in many UK estuaries and coasts and appears likely to influence species composition in the biotope (NBN Gateway 2016). This species prefers lower salinities and is typical of brackish waters (Kotta et al., 2013) and is therefore not considered a threat to this biotope where salinities are unaltered from the usual full salinity conditions.

Sensitivity assessment. The sediments characterizing this biotope are mobile and frequent disturbance limits the establishment of marine and coastal invasive non-indigenous species. The habitat conditions are unsuitable for most species, including Crepidula fornicata, which is unlikely to become established due to the mobility of the sediment. The unsuitable habitat conditions are exemplified by the low species richness characterizing this biotope. Therefore, this biotope is considered to have 'High' resistance to this pressure and 'High' resilience (by default) and is assessed as 'Not sensitive' to this pressure. 

Introduction of microbial pathogens

Benchmark. The introduction of relevant microbial pathogens or metazoan disease vectors to an area where they are currently not present (e.g. Martelia refringens and Bonamia, Avian influenza virus, viral Haemorrhagic Septicaemia virus). Further detail

Evidence

 Amphipods may also be infected by a number of parasites or pathogens that alter population numbers through changes in host condition, growth, behaviour and reproduction (Green Extabe & Ford, 2014). Infection by acanthocephalan larvae, for example, may alter behaviour and responses of gammarid amphipods (Bethel & Holmes, 1977). 

No evidence was found for pathogen/parasite outbreaks that may result in mass-mortalities in the characterizing species and this pressure is not assessed.

Removal of target species

Benchmark. Removal of species targeted by fishery, shellfishery or harvesting at a commercial or recreational scale. Further detail

Evidence

Intertidal populations of Nepthys cirrosa may be targeted by bait diggers.  There is limited information on the effect of digging directly on Nephtys cirrosa populations, however there is evidence on effects on another Nephtys species: Nephtys hombergii. Nephtys hombergii is directly removed through commercial bait digging and by recreational anglers and abundance significantly decreased in areas of the Solent, UK, where bait digging (primarily for Nereis virens) had occurred (Watson et al. 2007). Recovery of Nephtys hombergii has been assessed to be very high as re-population would occur initially relatively rapidly via adult migration and later by larval recruitment. Dittman et al. (1999) observed that Nephtys hombergii was amongst the macrofauna that colonized experimentally disturbed tidal flats within two weeks of the disturbance that caused defaunation of the sediment. However, if sediment is damaged recovery is likely to be slower, for instance Nephtys hombergii abundance was reduced by 50% in areas where tractor towed cockle harvesting was undertaken on experimental plots in Burry inlet, south Wales, and had not recovered after 86 days (Ferns et al., 2000).

Sensitivity assessment. Although Nephtys cirrosa may be targeted by bait differs where this species occurs intertidally, subtidal populations are not considered to be impacted unless there was a change in emergence regime. This pressure is, therefore considered to be 'Not relevant' to the assessed biotope.

Removal of non-target species

Benchmark. Removal of features or incidental non-targeted catch (by-catch) through targeted fishery, shellfishery or harvesting at a commercial or recreational scale. Further detail

Evidence

The loss of the key characterizing species through unintentional removal would alter the character of the biotope. The ecosystem services such as secondary production and food for higher trophic levels would be lost. The polychaete Nephtys cirrosa and the amphipods are predated on by flat fish and other invertebrate predators during tidal inundation (Speybroeck et al., 2007; Van Tomme et al., 2014).

Sensitivity assessment. Biotope resistance to loss of the characterizing species is assessed as ‘Low’ as the burrowing lifestyle and mobility of species mean that a proportion of the population may escape incidental removal. Resilience is assessed as ‘High’ based on in-situ recovery and migration from adjacent populations and sensitivity is therefore assessed as ‘Low’. Despite the loss of a high proportion of the characterizing species the biotope would probably still be classified as belonging to SS.SSa.IFiSa.IMoSa biotope as some examples, particularly those that are very exposed to wave action, contain few species at low abundance (JNCC, 2015).