The Marine Life Information Network

Temperature increase (local)

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

Evidence

There is no information on the response of the biotope to an increase in temperature. The important or key characteristic species are widely distributed in the north east Atlantic, with Parvicardium ovale occurring from Iceland to the Mediterranean and Canary Islands (Hayward & Ryland, 1995b). No specific information regarding the distribution of Ampharete falcata was found, but the congener Ampharete acutifrons occurs from the Artic to the Mediterranean (Hayward & Ryland, 1995b).

Schückel et al. (2010) investigated the temporal variability of macrofauna communities in the northern North Sea in relation to changes in temperature and/or changes in hydrography. The authors observed a significant negative correlation between total macrofaunal abundance, including of Ampharete falcata, and mean surface temperature (SST). Mean surface temperatures recorded varied between 13.4-16.6°C. Mean bottom temperatures remained more stable and varied between 6.7-7.6°C. The authors observed a strong decrease in mean abundance as a result of increased SST where increased SST mainly enhanced stratification, and contributed to a decrease in food availability for the benthic community at the site. 

Parvicardium ovale was recorded in Norway in waters with annual temperatures varying between 1-11°C (Gulliksen & Bahr, 2001). Holte et al. (2005) investigated the variations in soft bottom macrofauna from stratified Norwegian basins. Pavicardium ovale occurred at the study sites, which experienced temperatures between 0.5-14°C.

Sensitivity assessment: The characterizing species of the biotope are widely distributed and likely to occur both north and south of the British Isles, where typical surface water temperatures vary seasonally from 4-19°C (Huthnance, 2010). Although no information was found on the maximum temperature tolerated by the characterizing species, it is likely that Ampharete falcata and Parvicardium ovale are able to resist a long-term increase in temperature of 2°C. However, the biotope occurs in the margins of stratified seas (Connor et al., 2004), so an increase in temperature could result in enhanced stratification and consequently in restriction of food availability for the biotope community. Although stratification is not an instantaneous process, it may develop over time scales of hours in coastal waters (Nunes Vaz, 1990) so a short-term increase of 5°C may result in some adverse implications for the characterizing species. Resistance is therefore assessed as Medium (loss <25%), but with a Low confidence. Resilience is likely to be High so the biotope is considered to have Low sensitivity to an increase in temperature at the pressure benchmark level.

Temperature decrease (local)

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

Evidence

There is no information on the response of the biotope to a decrease in temperature. Species are widely distributed in the north east Atlantic, with Parvicardium ovale occurring from Iceland to the Mediterranean and Canary Islands (Hayward & Ryland, 1995b). No specific information regarding the distribution of Ampharete falcata was found, but the congener Ampharete acutifrons occurs from the Artic to the Mediterranean (Hayward & Ryland, 1995b).

Schückel et al. (2010) investigated the temporal variability of macrofauna communities in the northern North Sea in relation to changes in temperature and/or changes in hydrography. The authors observed a significant negative correlation between total macrofaunal abundance, including of Ampharete falcata, and mean surface temperature (SST). Mean surface temperatures recorded varied between 13.4-16.6°C. Mean bottom temperatures remained more stable and varied between 6.7-7.6°C. The authors observed a strong decrease in mean abundance as a result of increased SST where increased SST mainly enhanced stratification, and contributed to a decrease in food availability for the benthic community at the site. And also that cold-temperate species, such as Ampharete falcata, are favoured by thermoclines and water mixing at different depths may affect small spatial patterns of macrofaunal species independent of increasing SST.

Méndez (2007) investigated the distribution of deep-water polychaete fauna in the Gulf of California according to varying environmental parameters, including depth, temperature, dissolved oxygen. The authors found that dominant species, including Ampharete spp. occurred within limited ranges of environmental parameters, not occurring at temperatures below 2°C.

Parvicardium ovale was recorded in Norway in waters with annual temperatures varying between 1-11°C (Gulliksen & Barh, 2001). Holte et al. (2005) investigated the variations in soft bottom macrofauna from stratified Norwegian basins. Pavicardium ovale occurred at the study sites, which experienced temperatures between 0.5-14°C.

Sensitivity assessment: The characterizing species of the biotope are widely distributed and likely to occur both north and south of the British Isles, where typical surface water temperatures vary seasonally from 4-19°C (Huthnance, 2010). Although no information was found on the minimum temperature tolerated by the characterizing species, it is likely that Ampharete falcata and Parvicardium ovale are able to resist a long-term decrease in temperature of 2°C or 5°C in the short-term. Furthermore, the biotope occurs in the margins of stratified seas (Connor et al., 2004), so a decrease in temperature could result in reduced stratification and consequently enhanced food availability for the biotope community. Resistance and resilience are therefore assessed as High and the biotope is judged as Not Sensitive.

Salinity increase (local)

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

Evidence

SS.SMu.OMu.AfalPova is found within fully marine subtidal locations and it is highly unlikely that the biotope would experience hypersaline conditions. Although the study did not involve hypersaline conditions, Zettler et al. (2007) compared indices of ecological quality of benthic biodiversity along salinity gradients in the Baltic Sea, and suggested that Parvicardium ovale was not able to deal with wide variations in salinity.

Sensitivity assessment: There is little direct evidence of the effects of hypersaline conditions on the characterizing species of this biotope, Ampharete falcata and Parvicardium ovale. However, it is unlikely that the biotope community would be able to resist an increase in salinity to >40 psu, resulting in mortality of the characterizing species. Resistance is therefore assessed as Low (loss of 25-75%) but with low confidence. Once normal conditions are resumed, resilience is probably High so that sensitivity is therefore assessed as Low.

Salinity decrease (local)

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

Evidence

SS.SMu.OMu.AfalPova is found within fully marine subtidal locations and it is highly unlikely that the biotope would experience conditions of hyposalinity. However, it is likely that key components of the biotope community would not be resistant of a decrease in salinity. For example, Zettler et al. (2007) compared indices of ecological quality of benthic biodiversity along salinity gradients in the Baltic Sea, where salinities varied from 1.5-27.8 psu. Parvicardium ovale was considered not able to deal with the wide variations in salinity that occur in the study site. However, Parvicardium ovale was recorded in the Baltic Sea at near bottom salinity of 12-18 PSU (Gogina et al., 2010).

Sensitivity assessment: Based on the evidence presented, it is likely that characterizing species Parvicardium ovale would resist a decrease in salinity from full to reduced conditions. No direct evidence of the effects of hyposaline conditions on characterizing species Ampharete falcata was found. Based on the species offshore preferences of between 30-90 m (Heath, 2005) it is unlikely that Ampharete falcata would be adapted and the community is unlikely to resist a decrease in salinity at the pressure benchmark level. As Ampharete is considered a key characterizing and structuring species of this biotope, loss of this species would result in the biotope being lost. Resistance is therefore assessed as Low (loss of 25-75%) but with low confidence. Once prior conditions resume, resilience is probably High so that sensitivity is, therefore, assessed as Low.

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

The hydrographic regime is an important structuring factor in sedimentary habitats. The most damaging effect of increased flow rate (above the pressure benchmark) could be the erosion of the substratum as this could eventually lead to loss of the habitat. Increased water flow rates are likely to change the sediment characteristics in which the species live, primarily by re-suspending and preventing deposition of finer particles (Hiscock, 1983). Tube building species Ampharete falcata is likely to depend on the weak (<0.5 m/s) tidal streams that characterize the biotope (Connor et al., 2004), as it allows development of the fine sediment habitat. Additionally, the consequent lack of deposition of particulate matter at the sediment surface would reduce food availability. Decreased water movement would result in increased deposition of suspended sediment (Hiscock, 1983). An increased rate of siltation resulting from a decrease in water flow may result in an increase in food availability for the characterizing species and therefore growth and reproduction may be enhanced, but only if food was previously limiting.

Cooper et al. (2007) investigated recovery of the seabed following marine aggregate dredging on the south east coast of England. The maximum spring tidal current velocity was ca. 1.3 m/s. The authors confirmed that the sediment became coarser with increased dredging intensity and that the seabed appeared extremely uneven, with these effects appearing to persist at least 8 years after cessation of dredging activities. Ampharete spp. were recorded from the study site characterized by high intensity of dredging activities soon after cessation, possibly because of the opportunistic life habits of this taxa.

On the other hand, Parvicardium ovale has been recorded in Norway in waters with current velocities up to 1.7 m/s (Gulliksen & Barh, 2001).

Furthermore, the biotope occurs near margins of stratified seas (Connor et al., 2004). Changes in water flow are likely to affect the mixing of waters in the area and influence the extent of the stratified waters, consequently having an impact on the biotope. Increased flow rates may enhance mixing and allow expansion of the biotope’s boundaries where suitable substratum occurs.

Sensitivity assessment: Sand particles are most easily eroded and likely to be eroded at about 0.20 m/s (based on Hjulström-Sundborg diagram, Sundborg, 1956). Although having a smaller grain size than sand, silts and clays require greater critical erosion velocities because of their cohesiveness. SS.SMu.OMu.AfalPova occurs in weak tidal streams (0.5 m/s) in localised areas on a crucial point on a depositional gradient between areas of tide-swept mobile sands and quiescent stratifying muds (Connor et al., 2004). Based on the evidence presented, it is likely that characterizing species Parvicardium ovale would resist changes in water flow, and no direct evidence of the maximum flow velocity tolerance of characterizing species Ampharete falcata was found. Although changes in water flow (above the benchmark) would be likely to change the sedimentary regime in the biotope and consequently have implications on tube building Ampharete falcata, the cohesive nature of the sandy muds that characterize the biotope is likely to provide some protection to changes in water flow at the pressure benchmark. Resistance and resilience are therefore assessed as High and the biotope considered Not Sensitive to a change in water flow at the pressure benchmark level.

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

Changes in emergence are Not Relevant to the biotope, which is restricted to fully subtidal/circalittoral conditions. The pressure benchmark is relevant only to littoral and shallow sublittoral fringe 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

Potentially the most damaging effect of increased wave heights would be the erosion of the fine sediment substratum as this could eventually lead to loss of the habitat. Furthermore, changes in wave exposure may influence the supply of particulate matter for tube building and feeding activities of the characterizing species. Decreases in wave exposure may influence the supply of particulate matter because wave action may have an important role in re-suspending the sediment that is required by the species to build its tubes. Food supplies may also be reduced, affecting growth and fecundity of the species.

Sensitivity assessment: No direct evidence of the specific tolerances of the characterizing species to changes in wave exposure was found. The depth of the biotope (>50 m) is likely to protect the biotope from anything other than the most severe change in wave action. Hiscock (1983) suggested that a Force 8 Gale could result in oscillatory wave induced water flow at 80 m of 0.09 m/s or ca 0.4 m/s at 50 m. A change in significant wave height of 3-5% is roughly equivalent to a change form from force 3-4. Therefore, it is unlikely to be significant in deep water biotopes. Resistance and resilience are therefore assessed as High, and the biotope is considered Not Sensitive at the benchmark level, but with low confidence.

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.

There is no information on the resistance of the key species in the biotope. Experimental studies with various species suggests that polychaete worms are quite tolerant of heavy metals (Bryan, 1984).

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

The biotope is considered to be 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

The biotope is considered to be This pressure is Not assessed but evidence is presented where available.

Radionuclide contamination

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

Evidence

No Evidence is available on which to assess this pressure.

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

The biotope is dominated by opportunistic small bivalves and polychaetes near margins of stratified seas, which suggests that the biological community is likely to be adapted to the adverse effects of stratification. Variations in environmental conditions may cause the stratification boundaries to shift, potentially resulting in episodes on hypoxia in the biotope.

Méndez (2007) investigated the distribution of deep-water polychaete fauna according to varying environmental parameters, including dissolved oxygen. The author found that dominant species, including Ampharete spp. occurred within limited ranges of environmental parameters, not occurring at oxygen levels below ca 0.8 mg/l. Gogina et al. (2010a) suggested that Parvicardium ovale showed a strong positive correlation with dissolved oxygen. Holte et al. (2005) recorded Parvicardium ovale from stratified Norwegian basins with minimum oxygen values in deep water as low as 2.2 mg/l. Rosenberg et al. (1991) exposed benthic species from the NE Atlantic to oxygen concentrations of around 1 mg/l for several weeks, including species of small bivalves. After 11 days in hypoxic conditions, bivalve individuals were still alive, although individuals showed increased stretching of syphon out of the sediment. It is possible the Parvicardium ovale would deal with low oxygen in a similar way.

Sensitivity assessment: Direct evidence regarding the effect of de-oxygenation on the key species in the biotope or the biotope as a whole is limited. Cole et al. (1999) suggest possible adverse effects on marine species below 4 mg/l and probable adverse effects below 2 mg/l. Based on the evidence presented, the characterizing species are likely to only be affected by severe deoxygenation episodes. Resistance to de-oxygenation at the pressure benchmark level is likely to be High. Resilience of the biotope is likely to also be High and the biotope is therefore considered Not Sensitive to exposure to dissolved oxygen concentration of less than or equal to 2 mg/l for 1 week.

Nutrient enrichment

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

Evidence

Increased nutrients are most likely to affect abundance of phytoplankton which may include toxic algae (OSPAR, 2009). This primary effect resulting from elevated nutrients will impact upon other biological elements or features (e.g. toxins produced by phytoplankton blooms or de-oxygenation of sediments) and may lead to ‘undesirable disturbance’ to the structure and functioning of the ecosystem. With enhanced primary productivity in the water column, organic detritus that falls to the seabed may also be enhanced, which may be utilized by the deposit feeders in the community.

Parvicardium exiguum and Ampharete grubei are both found in areas rich in silt and organic content (Lastra et al., 1993; Holme, 1949) and so the key species are likely to be similar. Hiscock et al. (2005a) suggested that Ampharete spp. might be favoured by nutrient enrichment, but the overall species diversity is likely to decline.

Sensitivity assessment: The community, and hence the biotopes, may change to one dominated by nutrient enrichment resistant species, in particular polychaete worms. However, the biotope is considered to be Not Sensitive at the pressure benchmark that assumes compliance with WFD good status.

Organic enrichment

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

Evidence

Borja et al. (2000) Ampharete spp. and Parvicardium ovale to their Ecological Group I ‘Species very sensitive to organic enrichment and present under unpolluted conditions (initial state)’. These results confirm suggestions that Parvicardium ovale has a strong negative correlation with total organic content (Gogina et al., 2010a). Furthermore, Holte et al. (2005) investigated the variations in soft bottom macrofauna from stratified Norwegian basins. Parvicardium ovale showed preferences for open areas and was recorded in highest abundances at sites where total organic carbon (TOC) was relatively low (10 mg/g) compared to sites where it was absent with TOC as high as 69 mg/g. However, Parvicardium ovale has been recorded in intertidal mudflats supporting high primary production in France, with an annual total primary production input of 466 gC/m²/yr, of which only 157 gC/m²/yr was exported (Leguerrier et al., 2003). These results suggest that the community under study had approx. 300 gC/m²/yr available, but it was not clear of the exact proportion of organic matter reaching the seafloor.

Sensitivity assessment: SS.SMu.OMu.AfalPova is found in areas of fine sediment where organic content will generally be higher than coarse sediments. Parvicardium exiguum and Ampharete grubei are both found in areas rich in silt and organic content (Lastra et al., 1993; Holme, 1949) and so the key species are likely to be similar. However, the evidence presented is not directly comparable to the pressure benchmark. It is however likely that some mortality of the characterizing species is likely to occur as a result of organic enrichment. Resilience is therefore assessed as Low (25-75% loss), but with low confidence. Resilience is likely to the High and the overall sensitivity of the biotope judged as Low.

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

If the sediment that characterizes this biotope were replaced with rock substrata, this would represent a fundamental change to the physical character of the biotope. The characterizing species would no longer be supported and the biotope would be lost and/or re-classified.

Sensitivity assessment: Resistance to the pressure is considered None, and resilience Very Low, given the permanent nature of this pressure. Sensitivity has been assessed as 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 sediment type)

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

Evidence

SS.SMu.OMu.AfalPova is only recorded from cohesive sandy muds (Connor et al., 2004), and characterizing species Ampharete falcata exhibits specific preferences for fine sediment substrata that provides the material for tube building activities. In the Baltic Sea, Parvicardium ovale has been shown to have a strong positive correlation with medium grain size (Gogina et al., 2010a).

Sensitivity assessment: In SS.SMu.OMu.AfalPova, change in Folk class from mud and sandy mud to sand or muddy sand (based on the Long, 2006 simplification)  would mean a change from mud and sandy mud to sand or muddy sand, or to gravelly mixed sediment. The characterizing species are unlikely to be resistant of such a change in sediment type, no longer being supported, and hence lost from the biotope. The biotope is likely to be lost, so resistance is therefore assessed as None and resilience as Very Low, given the permanent nature of this pressure. The biotope is considered to have High sensitivity to a change in seabed type by one Folk class.

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

Sedimentary communities are likely to be highly intolerant of substratum removal, which will lead to partial or complete de-faunation, expose underlying sediment which may be anoxic and/or of a different character and lead to changes in the topography of the area (Dernie et al., 2003). Any remaining species, given their new position at the sediment/water interface, may be exposed to unsuitable conditions. Newell et al. (1998) state that removal of 0.5 m depth of sediment is likely to eliminate benthos from the affected area. Some epifaunal and swimming species may be able to avoid this pressure. Removal of 30 cm of sediment will remove species that occur at the surface and within the upper layers of sediment, such as the characterizing species of this biotope. For example, dredging operations were shown to affect large infaunal and epifaunal species, decrease sessile polychaete abundance and reduce the numbers of burrowing heart urchins (Eleftheriou & Robertson, 1992). For example, Cooper et al. (2007) investigated recovery of the seabed following marine aggregate dredging on the south-east coast of England. The authors confirmed that the sediment became coarser with increased dredging intensity and that the seabed appeared extremely uneven, with these effects appearing to persist at least 8 years after cessation of dredging activities. Ampharete spp. were recorded from the study site characterized by high intensity of dredging activities soon (<1 year) after cessation of dredging.

Sensitivity assessment: Extraction of 30 cm of sediment will remove the characterizing biological component of the biotope so resistance is assessed as None. Newell et al. (1998) indicate that local hydrodynamics (currents and wave action) and sediment characteristics (mobility and supply) strongly influence the recovery of soft sediment habitats. The biotope occurs in low energy environments, so resilience is therefore judged as Medium (see resilience section). Sensitivity has been 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

SS.SMu.OMu.AfalPova can be affected by fishing activity in areas such as the northern Irish Sea, where the community may also contain Nephrops norvegicus (Connor et al., 2004). Fauna that inhabit or construct tubes, such as characterizing species Ampharete falcata are likely to be particularly vulnerable to damage or disturbance by beam trawls (Kaiser & Spencer, 1996). Furthermore, Parvicardium ovale lives infaunally in soft sediment, usually within a few centimetres of the sediment surface. Physical disturbance, such as dredging or dragging an anchor, would be likely to penetrate the upper few centimetres of the sediment and cause physical damage to the small bivalves.

Ball et al. (2000a) investigated the long- and short-term consequences of a Nephrops trawl fishery on benthos and environment of the Irish Sea comparing samples taken before and after fishing activity. Of the two inshore and offshore sites analysed, that both occurred in similar fine sand and silt-clay sediment, the offshore station occurs at a depth and sediment type similar to that of this biotope and a sparse benthic macrofauna was observed dominated by small polychaetes and a few crustaceans and bivalves. Ampharete falcata was among the species present at the control site but absent from the fished grounds at both inshore and offshore sites. However, Ampharete acutifrons was among the species found at the fished grounds but not at the control sites. Overall, the authors found that the numbers of species, species richness and biomass had all dropped after trawling.

Kaiser et al. (2006) undertook a meta-analysis of different fishing gears on a range of habitats. The authors concluded that the footprint of the impact and the recovery of communities varied with gear and habitat types. For example, mud habitats were shown to have substantial initial impacts by otter trawling but the effects tended to be short lived with an apparent long-term positive post-trawl disturbance response from the increase of small bodied fauna.

Furthermore, SS.SMu.OMu.AfalPova occurs in cohesive sandy muds (Connor et al., 2004). Abrasion events caused by a passing fishing gear, or scour by objects on the seabed surface are likely to have marked impacts on the substratum and cause turbulent resuspension of surface sediments. When used over fine muddy sediments, trawls are often fitted with shoes designed to prevent the boards digging too far into the sediment (M.J. Kaiser, pers. obs., cited in Jennings & Kaiser, 1998). The effects may persist for variable lengths of time depending on tidal strength and currents and may result in a loss of biological organization and reduce species richness (Hall, 1994; Bergman & Van Santbrink, 2000; Reiss et al., 2009) (see change in suspended solids and smothering pressures).

Sensitivity assessment: The characterizing species are considered likely to be damaged and removed by abrasion, particularly the turf of Ampharete falcata as these protrude from the muddy sediments and are not physically robust. Resistance to abrasion is therefore assessed as None. Resilience of the biotope is likely to be Medium given that the low energy of the biotope may impede immediate recolonization by the characterizing species (see resilience). The biotope is therefore considered to have Medium sensitivity to abrasion or disturbance of the surface of the seabed.

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

Activities that disturb the surface of the mat and penetrate below the surface would remove a significant proportion of the turf of Ampharete falcata, as well as remove/damage infaunal species such as Parvicardium ovale within the direct area of impact.

Furthermore, penetrative events caused by a passing fishing gear are also likely to have marked impacts on the substratum and cause turbulent re-suspension of surface sediments (see abrasion pressure). When used over fine muddy sediments, trawls are often fitted with shoes designed to prevent the boards digging too far into the sediment (M.J. Kaiser, pers. obs., cited in Jennings & Kaiser, 1998). The effects may persist for variable lengths of time depending on tidal strength and currents and may result in a loss of biological organization and reduce species richness (Hall, 1994; Bergman & Van Santbrink, 2000; Reiss et al., 2009) (see change in suspended solids and smothering pressures).

Sensitivity assessment: The biotope could be lost or severely damaged, depending on the scale of the activity (see abrasion pressure). Therefore, a resistance of None is suggested. Resilience is probably Medium, and therefore the biotope’s sensitivity to this pressure ifslikely to be Medium.

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 biotope occurs in sheltered areas, in fine sediments, subject to high suspended sediment loads. Therefore, the important characteristic species are unlikely to be impacted by an increase in suspended sediments. Suspended sediment and siltation of particles are likely to be important for tube building in Ampharete falcata, so a decrease in suspended solids may reduce material available for tube building. For most benthic deposit feeders, food is suggested to be a limiting factor for body and gonad growth, at least between events of sedimentation of fresh organic matter (Hargrave, 1980; Tenore, 1988). Consequently, increased organic matter in suspension that is deposited may enhance food supply on the seabed. A decrease in the suspended sediment and hence siltation may reduce the flux of particulate material to the seabed. Since this includes organic matter, the supply of food to the biotopes would probably also be reduced.

Sensitivity assessment: An increase in suspended solids at the pressure benchmark level is unlikely to affect the characterizing species of this offshore biotope. Although a decrease in suspended matter in the biotope could result in limitation of material for tube building activity of Ampharete falcata, the species is not likely to suffer mortality due to its ability to also use sand for tube building. Resistance and resilience of the biotope are assessed as High, so the biotope is considered Not Sensitive to a change in suspended solids at the pressure benchmark level.

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

Smothering by 5 cm of sediment is likely to lead to the death of some of the organisms in the biotope. Ampharete falcata is a small polychaete worm up to 18 mm in length (Heath, 2005). The populations of this tube dwelling polychaete will probably be unable to feed or respire resulting in some mortality. Some individuals may be able to reborrow through the sediment but survival is probably dependent on the speed at which new tubes can be built, otherwise mortality may occur due to predation. Some of the burrowing fauna, such as the small bivalve Parvicardium ovale, is unlikely to be affected by smothering beyond re-establishing burrow openings or moving up through the sediment. Although, there is evidence of synergistic effects on burrowing activity of marine benthos and mortality with changes in time of burial, sediment depth, sediment type and temperature (Maurer et al., 1986).

Sensitivity assessment: No direct evidence was found regarding the ability of the characterizing species to deal with this pressure. However, some mortality of characterizing species Ampharete falcata is likely to occur as a result of a ‘light’ deposition of fine sediment in a discrete event. Resistance is therefore assessed as Low (loss 25-75%), with low confidence. However, resilience is likely to be High and the biotope is considered to have Low sensitivity at the pressure benchmark level.

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

Smothering by 30 cm of sediment is likely to lead to the death of some of the organisms in the biotope. Ampharete falcata is a small polychaete worm up to 18 mm in length (Heath, 2005). The populations of this tube dwelling polychaete will probably be unable to feed or respire resulting in some mortality, although, polychaete species have been reported to migrate through depositions of sediment greater than the benchmark (30 cm of fine material added to the seabed in a single discrete event) (Maurer et al., 1982). It is unclear whether the small bivalve Parvicardium ovale would be able to migrate vertically through the deposited sediment to re-establishing burrow openings.

Sensitivity assessment: No direct evidence was found regarding the ability of the characterizing species to deal with this pressure. However, some mortality of both characterizing species Ampharete falcata and Parvicardium ovale is likely to occur as a result of a ‘heavy’ deposition of fine sediment in a discrete event. Resistance is therefore assessed as Low (loss 25-75%), with low confidence. Resilience is however likely to be High and the biotope is considered to have Low sensitivity at the pressure benchmark level.

Litter

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

Evidence

Not assessed.

Electromagnetic changes

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

Evidence

No Evidence is available on which to assess this pressure.

Underwater noise changes

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

Evidence

Ampharete falcata, Parvicardium ovale and some of the other species in the biotope may respond to vibrations from predators or excavation by retracting their palps into their tubes. However, the characterizing species are unlikely to be affected by noise pollution and so the biotope is assessed as Not Sensitive.

Introduction of light or shading

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

Evidence

SS.SMu.OMu.AfalPova is a circalittoral biotope (Connor et al., 2004) and therefore not directly dependent on sunlight. 

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

Not Relevant to biotopes restricted to open waters.

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 biotope occurs in deep water where available light is very low. Of the characterizing species, Parvicardium ovale lives infaunally and Ampharete falcata has only two simple eyespots, so have no or poor visual perception and unlikely to be affected by visual disturbance such as shading. Therefreo, this pressure is probably 'Not relevant' to this biotope.

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

The key characterizing species in the biotope are not cultivated or likely to be translocated. This pressure is therefore considered Not Relevant.

Introduction or spread of invasive non-indigenous species

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

Evidence

Although several non-native species of polychaete and mollusc have invaded British waters there are none that are likely to affect SS.SMu.OMu.AfalPova. Although there is always the potential for this to occur, this pressure is considered Not Relevant.

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

A record of the parasitic polychaete Heamatocleptes terebellidis, normally associated with lamella-worm Terebellides stroemmii, has also been recorded from Ampharete falcata in the Irish Sea (O’Reilly, 2016). The authors recognized that the parasite is likely to be under-recorded but probably widely distributed due to its clandestine habits, as it has only been recorded from Sweden, where it was originally recorded. The parasite is known to live inside the coelom of Terebellides stroemmii, and other polychaetes. No further information of the potential impacts on the polychaetes’ health and survival were provided.

Sensitivity assessment: No direct evidence of the biotopes being affected by the introduction of microbial pathogens was found as with which to assess this pressure.

Removal of target species

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

Evidence

It is extremely unlikely that any of the species indicative of sensitivity would be targeted for extraction. Even in areas where Nephrops norvegicus is present, trawlers are likely to avoid clogging of the nets by the high densities of Ampharete tubes. This pressure is therefore considered Not Relevant.

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

SS.SMu.OMu.AfalPova can be affected by fishing activity in areas such as the northern Irish Sea, where the community may also contain Nephrops norvegicus (Connor et al., 2004). Fauna that inhabit or construct tubes, such as characterizing species Ampharete falcata are likely to be particularly vulnerable to damage or disturbance by beam trawls (Kaiser & Spencer, 1996). Direct, physical impacts are assessed through the abrasion and penetration of the seabed pressures, while this pressure considers the ecological or biological effects of by-catch. Species in this biotope, including the characterizing species Ampharete falcata and Parvicardium ovale, may be damaged or directly removed by static or mobile gears that are targeting other species (see abrasion and penetration pressures). Loss of the Ampharete falcata turf, along with the dense community of Parvicardium ovale, would alter the character of the biotope resulting in re-classification, and would alter the physical structure of the habitat resulting in the loss of the ecosystem functions such as secondary production performed by these species.

Sensitivity assessment: Removal of the characterizing species would result in the biotope being lost or re-classified. Thus, the biotope is considered to have a resistance of None to this pressure and to have Medium resilience, resulting in the sensitivity being judged as Medium.