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

Intertidal species are exposed to extremes of high and low air temperatures during periods of emersion. They must also be able to cope with sharp temperature fluctuations over a short period of time during the tidal cycle. In winter air temperatures are colder than the sea, conversely in summer air temperatures are much warmer than the sea. Species that occur in the intertidal are therefore generally adapted to tolerate a range of temperatures, with the width of the thermal niche positively correlated with the height of the shore that the animal usually occurs at (Davenport & Davenport, 2005).

No empirical evidence was found to assess the tolerant of Echinogammarus incertae sedis planicrurus to temperature increases. Bell (1995) summarised the distribution of Echinogammarus incertae sedis planicrurus (as Pectenogammarus planicrurus) based on previous studies. Both Stock (1982) and Lincoln (1979) identified Echinogammarus incertae sedis planicrurus as a southern species and described its distribution as a ‘west-Mediterranean Lusitanian type’ and ‘Mediterranean type’ respectively.  The south and west coasts of Britain and Ireland form the northern limit of distribution. Populations in different areas are likely to have acclimated to the prevailing conditions and so the distributions are interpreted cautiously and confidence in this assessment is ‘Low’. During the summer, the population turnover of Echinogammarus incertae sedis planicrurus is high; a female might typically live for four weeks whilst those that survive and overwinter may live as long as eight months (Bell, 1992) and changes in temperature may result in increased reproductive outoput during warmer periods.

Sensitivity assessment. Echinogammarus incertae sedis planicrurus has a southern distribution and can be found on the upper shore where they are likely to experience wide temperature fluctuations during the tidal cycle. The sediments are coarse and porous so that little protection may be gained from sediment buffering. Acute temperature increases (5^oC for one month) may exceed tolerances in the summer months or in the winter a sudden increase in temperature may also affect cold acclimated individuals. Exposure to warmer waters during the tidal cycle will, however, be brief (particularly for upper shore populations) and animals may migrate either downwards within sediments or up the shore to avoid unfavourable conditions. Resistance to both an acute and chronic increase in temperature (2^oC for one year)  is therefore assessed as ‘High’ and resilience as ‘High’ so that the biotope is assessed as ‘Not sensitive’.

Temperature decrease (local)

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

Evidence

Records of Echinogammarus incertae sedis planicrurus have not been reported to the north of the British Isles. Bell (1995) suggested that the northerly limit to the distribution of Echinogammarus incertae sedis planicrurus (as Pectenogammarus planicrurus) is defined by the lowest temperature at which its semi-annual life history of producing small broods with early maturation is possible. A chronic decrease of 2°C may, therefore, affect the viability of the species. Furthermore, in the intertidal acute decreases in temperature, e.g. during a severe winter, may cause freezing of the species within the substratum.

Amphipods are mobile and can escape local unfavourable conditions by migrating into sediments or by moving within the habitat. The species may, therefore, be able to escape from colder waters during tidal emersion by migrating up the shore (as long as sediments are not frozen). During the summer, the population turnover of Echinogammarus incertae sedis planicrurus is high; a female might typically live for four weeks whilst those that survive and overwinter may live as long as eight months (Bell, 1992). decreases in temperature may, therefore, reduce reproductive outputs and population size.

Sensitivity assessment. Echinogammarus incertae sedis planicrurus is considered sensitive to both a chronic and acute decrease in temperature, which may affect reproduction and population viability. Resistance is, therefore, assessed as ‘Low’ as the population may decrease in response to both pressure benchmarks. Resilience is assessed as ‘High’ as populations are likely to recover by in-situ reproduction (assuming some individuals survive) within two years following exposure, given the absence of competitors and predators in the habitat. The biotope is, therefore, judged to have low sensitivity to this pressure.

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, therefore, is assessed as a change to hypersaline conditions. No evidence was found to assess salinity tolerances of the key characterizing species Echinogammarus incertae sedis planicrurus. In its habitat, the species is unlikely to encounter hypersaline water (e.g. as a consequence of evaporation of 'pooled' surface water) as the coarse sand/gravel substratum is permeable and free draining.

Sensitivity assessment. ‘No evidence’ was found on which to base an assessment.

Salinity decrease (local)

Benchmark. A decrease 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), and the key characterizing species Echinogammarus incertae sedis planicrurus can withstand variable salinity (JNCC, 2015). Experimental evidence suggests that Echinogammarus incertae sedis planicrurus can withstand immersion in water of reduced salinity (20 psu) for 36 hours and freshwater for >18 hours (Morgan, 1970). Gravel sediments inhabited by Echinogammarus incertae sedis planicrurus are often associated with brackish waters and freshwater inputs (Stock, 1982; Bell, 1995). Thus it is likely that the important characterizing species of the biotope would survive periodic tidal flushing of the sediment with brackish or freshwater. As a mobile species, it would also probably move from conditions which it found intolerable.

Sensitivity assessment. Based on salinity tolerance of the key characterizing species Echinogammarus incertae sedis planicrurus biotope resistance is assessed as ‘High’ and resilience as ‘High’ (by default) so that the biotope is assessed as ‘Not sensitive’.

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

A typical feature of this habitat is its occurrence in the lee of obstacles such as rocky outcrops and groynes (JNCC, 2015) where it receives some protection from water flows.  The gravel habitat is non-cohesive and changes in water flow may increase or decrease movement of particles. Gravel shores are typically unstable and a decrease in water flow and/or wave exposure may lead to deposition of finer particles altering the sedimentary habitat and the associated biological assemblage. Increased water flow may increase instability and abrasion within sediments as the particles are moved, the shore profile may also change.

Sensitivity assessment. It should be noted that substrate coupled with wave action, rather than water flow, are likely to be key factors structuring the biotope. At the benchmark level, the change in water flow may result in some changes in sediment stability but these are not considered to significantly alter the biotope. Resistance is therefore assessed as ‘High’ and resilience as ‘High’ (by default) so that the biotope is assessed as ‘Not sensitive’.

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

This biotope is found on the mid and upper shore (JNCC, 2015). The coarse particles that characterize this biotope are free-draining and an increase in emergence could lead to desiccation On sandy shores (as in rocky shores) zonation of species occurs in relation to tidal height, talitrid amphipods tend to occur higher on the shore where sediments dry out at low tide while lower down the shore suspension feeding bivalves are more abundant in the damper sediments (McLachlan et al., 1995).

Echinogammarus incertae sedis planicrurus lives interstitially within the coarse sand/gravel and is probably sufficiently mobile within it to avoid adverse effects of a change in emergence regime. For instance, it can burrow deeper to avoid dryer surface layers. Some lateral migration is also possible to avoid unsuitable conditions. A change in emergence is likely to alter habitat suitability for examples of this biotope at the upper and lower shore height range. Biotopes at the upper end may be replaced by supralittoral strandline communities such as those dominated by macroalgal debris and talitrid amphipods if emergence increases, conversely decreased emergence may reduce habitat suitability for mid-shore biotopes and may lead to increased predation by fish during periods when the biotope is submerged (this may be compensated by reduced bird predation).

Sensitivity assessment. Overall resistance is assessed as ‘Medium’ as substratum rather than timing and duration of emergence is a key factor structuring the biotope changes in emergence may, however, lead to decreased habitat suitability for upper and lower shore examples. Resilience is assessed as ‘High’ based on migration from adjacent populations and biotope sensitivity is assessed as ‘Low’.

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

This biotope is found in habitats that are estimated to be moderately exposed to wave action (JNCC, 2015). A typical feature of this habitat is its occurrence in the lee of obstacles such as rocky outcrops and groynes (JNCC, 2015) where it receives some protection from wave action.  Wave exposure is an important physical factor determining the composition of the substratum and its stability which in turn changes suitability for the associated biological assemblage. Changes in wave exposure in the long-term result in changes in particle size and sorting and associated sediment properties and beach profile (Little, 2000).Where wave action is lower beaches tend to contain coarser sediments and to have steeper profiles and to dry out faster, whereas beaches exposed to higher levels of wave action consist of finer particles and are flatter (Little, 2000).

Sensitivity assessment. At the pressure benchmark, the biotope is considered to be unaffected, resistance is assessed as ‘High’ and resilience as ‘High’ (by default) so that the biotope is assessed as ‘Not sensitive’.

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.

No information concerning heavy metals and specific effects on Echinogammarus incertae sedis planicrurus was found. 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).

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.

Echinogammarus incertae sedis planicrurus is likely to have a high intolerance to hydrocarbon pollution. Oil penetrates deep in to coarse sand/gravel substratum. For example, the largest amount and least weathered oil arising from the Exxon Valdez oil tanker spill in Prince William Sound, Alaska was found eight years after the incident on gravel beaches at a depth between 25 and 50 cm (Hayes & Michel, 1999). Moderate wave exposure and unstable substratum characteristic of the biotope probably aid the penetration of oil in to the sediment. The smothering effect of oil is likely to cause mortality of Echinogammarus incertae sedis planicrurus in advance of toxic effects. Oil would coat the substratum particles, lessening the interstitial voids through which the amphipod moves and to which it would probably stick.

Small amounts of oil that can persist for decades in the intertidal zone of coarse-sediment beaches have been documented in a few well-studied cases (Owens et al., 2008). Oil that survives attenuation over the short-term (weeks to months) will persist until there is a change in the environmental conditions, as might occur where there is a seasonal storm-wave climate or as a beach undergoes long-term (erosional) changes. Oil residues can persist on the beach surface as tar mats, asphalt-like pavements, or as veneers on sediment particles or hard surfaces. Subsurface oil residues can persist in similar forms or as fill or partial fill of the pore spaces between coarse-sediment particles. Oil penetrates until it reaches fine-grained sediment, the water table, bedrock, or other penetration-limiting layers. Amounts of persistent oil are very small fractions of the volumes that were originally stranded and these protected residues can continue to biodegrade as they become thinner and more discontinuous.

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.

No information concerning synthetic chemical and specific effects on the important characterizing species Echinogammarus incertae sedis planicrurus was found. However, areas of the intertidal adjacent to industrialised and urbanised estuaries and coastlines may receive effluent discharges which contain a variety of synthetic contaminants. Bioaccumulation of conservative contaminants may occur within the infauna, but in coarse sand/gravel beaches contaminants are unlikely to accumulate owing to a relative absence of organic matter.

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

In its intertidal habitat, Echinogammarus incertae sedis planicrurus is inundated by the tide and subject to emergence that the species respires in both air and water. Within the interstitial environment of clean (low organic matter), coarse sand/gravel oxygen is unlikely to become limiting. The coarseness of the particles, bestows a high permeability, so that water percolates rapidly through and owing to the relative lack of organic matter, little oxygen is utilized for oxidization or respiration by micro-organisms (bacteria populations in sediments with a mean diameter greater than 0.2 mm typically support fewer bacteria (Dale, 1974). Sediments are, therefore, re-oxygenated during the ebb tide when sediments are exposed to air. Oxygen depletion tends to be a severe problem at all states of the tide on much finer grained beaches which support larger populations of bacteria (Hayward, 1994). At the benchmark level (a reduced dissolved oxygen concentration of 2 mg/l for 1 week) the characteristics of the sedimentary habitat make conditions of limiting oxygen unlikely. The important characterizing species Echinogammarus incertae sedis planicrurus, is also sufficiently mobile to migrate up-shore and avoid conditions that it finds inhospitable.

Sensitivity assessment. Biotope resistance is assessed as ‘High’, resilience is assessed as ‘High’ by default and the biotope is considered to be ‘Not sensitive’.

Nutrient enrichment

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

Evidence

The community is unlikely to be directly affected by an increase in the concentration of dissolved nutrients in the water column, as the food resource that the community utilizes is in the form of macroalgal debris. This pressure is therefore considered ‘Not relevant’.

Organic enrichment

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

Evidence

The biotope occurs in coarse sediments where wave action leads to particle sorting and fine sediments and organic matter are likely to be either flushed through the sediment owing to its porosity or re-suspended and removed. An input of organic matter at the pressure benchmark is therefore unlikely to alter the habitat type. Organic detritus may be used by Echinogammarus incertae sedis planicrurus as food (Bell, 1995) and thus this species may benefit from some input.

Sensitivity assessment. Biotope sensitivity is  assessed as ’High’ and resilience as ‘High’, so that the biotope is assessed as ‘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 oligochaetes that live buried within the sediment.

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

This biotope is found in gravel and very coarse sands (JNCC, 2015), a change between these sediment types would not alter habitat suitability for the key characterizing species or the habitat classification.  However, the biotope would be sensitive to a change to fine sands or sediments with high-levels of fine sediments, as these impair the burrowing ability of the key characterizing species Echinogammarus incertae sedis planicrurus (as Pectenogammarus planicrurus) (Morgan, 1970).

Sensitivity assessment. A change to a fine sediment would result in the biotope becoming unsuitable for the key characterizing species, which would be lost, with a change in biotope classification. Resistance is therefore assessed as ‘None’ and recovery as ‘Very low’ as a change at the pressure benchmark is permanent. Sensitivity is, therefore 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

The amphipod Echinogammarus incertae sedis planicrurus lives interstitially in the spaces between coarse sand/gravel particles. It is mobile within the substratum but would be removed along with the substratum if this was extracted to a depth of 30cm.

Sensitivity assessment. Removal of the sediment to 30 cm would remove the key characterizing species and its habitat. Resistance is therefore assessed as ‘None’. Resilience is assessed as ‘High’ if adjacent populations are present to support recolonization through adult migration and reproduction, so that sensitivity is assessed as ‘Low’. However, if populations were removed over a wide area recovery could be prolonged and is assessed as ‘Medium’, so that sensitivity s assessed as ‘Medium’. The less precautionary assessment is considered more representative but the caveats outlined in the resilience section should be considered and this assessment may underestimate sensitivity.

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

No evidence was found for abrasion impacts on the key characterizing species Echinogammarus incertae sedis planicrurus. However, a number of studies have assessed the effects of trampling on other intertidal amphipods and these assessments are used as a proxy. 

Comparisons between shores with low and high levels of trampling found that the amphipod Bathyporeia pelagica is sensitive to human trampling (Reyes-Martínez et al., 2015).  Changes in abundance of talitrid amphipods on urban beaches subject to high levels of recreational use was also observed by Bessa et al. (2014), this study compared abundances between samples taken ten years apart and thus the trends observed were not directly attributable to trampling vs beach cleaning or other pressures although they illustrate a general trend in density patterns as recreational use increases. Ugolini et al. (2008) carried out a controlled trampling experiment on Talitrus saltator. Plastic cylinders of 110 cm diameter (area 0.95 m²) were placed in the sand and all individuals trapped and counted, and 400 steps were made in a cylinder in 15 minutes after the amphipods had reburied. The trampling rate was based on observed number of beach users and therefore represents a realistic level of exposure. Alive sandhoppers were counted at the end of the experiment and 24 hours after. Trampling significantly reduced abundance of the amphipods and after 24 hours the percentage of surviving amphipods dropped to almost zero, while survival rates of control (untrampled) amphipods were unaffected. Abrasion and compaction can therefore kill buried amphipods within sediments.

Sensitivity assessment. The trampling experiment (Ugolini et al., 2008) represents a high intensity of abrasion with multiple steps on the sediment within a short time period. The experiment, does however, demonstrate that amphipods are sensitive to abrasion and compaction of the sediment and these results are observed by comparisons between heavily and lightly used areas (Reyes-Martínez et al., 2015; Bessa et al., 2014). Resistance to a single abrasion event is therefore assessed as ‘Low’ based on the characterizing species Echinogammarus incertae sedis planicrurus. 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).

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

No evidence was found for penetration and disturbance impacts on the key characterizing species Echinogammarus incertae sedis planicrurus. Based on the abrasion assessment, penetration and abrasion is considered likely to result in high-levels of mortality. Resistance is therefore assessed as ‘None;’ and resilience as ‘High’ so that sensitivity is assessed as ‘Medium’. Resilience may be lower where the pressure affects an entire population in areas with low population connectivity so that recovery is prolonged.

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

Echinogammarus incertae sedis planicrurus lives in the interstitial spaces within coarse sand/gravel and is unlikely to be directly affected by an increased concentration of suspended matter in the water column. The species feeds on macroalgal debris and other detritus and may be capable of feeding on suspended particles (J.D. Fish & L. Rickard, personal communication to M.C. Bell and cited in Bell, 1995).

Sensitivity assessment. Increased organic solids in suspension may provide food to the key characterizing species Echinogammarus incertae sedis planicrurus. Increased inorganic suspended solids may increase abrasion but it is likely that Echinogammarus incertae sedis planicrurus would withdraw into burrows or avoid areas of unsuitable conditions during tidal emersion and would be largely unaffected. Biotope resistance is assessed as ‘Medium’ as some effects on feeding and other behaviours may occur, resilience is assessed as ‘High’, following a return to usual conditions and sensitivity is assessed as ‘Low’. Indirect effects such as deposition and sediment change that may result as a result from increased suspended solids in the long-term are assessed separately. Indirect reduction of macroalgal productivity in adjacent impacted habitats resulting in reduced supply of macroalgae debris is possible but not assessed. 

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

As this biotope occurs in sheltered areas in the lee of obstacles (JNCC, 2015) a deposit of fine sediment may remain in-situ rather than being rapidly removed by wave action. If the deposited fine sediments are cohesive this can also prolong removal times .Deposited fine sediments may also become incorporated within coarse sands and gravels, reducing interstitial spaces and altering the sediment type.  Echinogammarus incertae sedis planicrurus is likely to be highly intolerant of smothering by 5 cm of fine sediment. There is a critical relationship between the size of interstitial spaces in the substratum through which the species can pass and the size of Echinogammarus incertae sedis planicrurus (Morgan, 1970). In selection experiments, the species demonstrated a clear preference for a sediment grades between 3-6 mm in diameter. Its passage through finer grades of substratum (<3 mm) was impaired and mortalities occurred as a consequence of suffocation (Morgan, 1970).   Similarly, 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. 

Sensitivity assessment.  A deposit of 5 cm fine sediment will prevent burrowing by Echinogammarus incertae sedis planicrurus, individuals within the sediment will not be able to reach the surface to feed and will suffocated, while individuals stranded on the surface will not be able to retreat into sediment and will become vulnerable to predation by birds. Resistance is therefore assessed as ‘None’. Resilience is assessed as ‘High’ if adjacent populations are present to support recolonization through adult migration and reproduction, so that sensitivity is assessed as ‘Low’. However, if populations were removed over a wide area recovery could be prolonged and is assessed as ‘Medium’, so that sensitivity s assessed as ‘Medium’. The less precautionary assessment is considered more representative but the caveats outlined in the resilience section should be considered and this assessment may underestimate sensitivity.

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

As this biotope occurs in sheltered areas in the lee of obstacles (JNCC, 2015), a deposit of fine sediment may remain in-situ rather than being rapidly removed by wave action. If the deposited fine sediments are cohesive this can also prolong removal times. Deposited fine sediments may also become incorporated within coarse sands and gravels, reducing interstitial spaces and altering the sediment type. Echinogammarus incertae sedis planicrurus is likely to be highly intolerant of smothering by 30 cm of fine sediment. There is a critical relationship between the size of interstitial spaces in the substratum through which the species can pass and the size of Echinogammarus incertae sedis planicrurus (Morgan, 1970). In selection experiments, the species demonstrated a clear preference for a sediment grades between 3-6 mm in diameter. Its passage through finer grades of substratum (<3 mm) was impaired and mortalities occurred as a consequence of suffocation. Similarly, 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. 

Sensitivity assessment. A deposit of 30 cm fine sediment will prevent burrowing by Echinogammarus incertae sedis planicrurus, individuals within the sediment will not be able to reach the surface to feed and will suffocated, while individuals stranded on the surface will not be able to retreat into sediment and will become vulnerable to predation by birds.  Resistance is therefore assessed as ‘None’. Resilience is assessed as ‘High’ if adjacent populations are present to support recolonization through adult migration and reproduction, so that sensitivity is assessed as ‘Low’. However, if populations were removed over a wide area recovery could be prolonged and is assessed as ‘Medium’, so that sensitivity s assessed as ‘Medium’. The less precautionary assessment is considered more representative but the caveats outlined in the resilience section should be considered and this assessment may underestimate sensitivity.

Litter

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

Evidence

Not assessed. No evidence was found for Echinogammarus incertae sedis planicrurus, however, the talitrid Orchestia gammarellus ingests microplastics in the size range 20-200 µm (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 information was found on orientation using geomagnetic fields by Echinogammarus incertae sedis planicrurus. However, 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).

No assessment was made of the sensitivity of Echinogammarus incertae sedis planicrurus due to the lack of evidence for this species. 

Underwater noise changes

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

Evidence

No evidence was found to assess this pressure.

Introduction of light or shading

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

Evidence

No specific evidence was found to assess sensitivity of Pectenogamarus planicrurus to this pressure. However, it is noted that orientation by light has been well studied for other intertidal amphipods (particularly the strandline dwelling species, 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 and the geomagnetic field (Scapini et al., 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 et al., 2014).  The introduction of light or an increase in shading could therefore alter behavioural patterns and navigation. As responses may be species specific or vary according to local factors or individual needs such as feeding, mating, it is not possible to provide a simple assessment for this species. Some sensitivity is however likely if incident light levels were altered. This will depend, however,  on the footprint and intensity of impact. Fanini et al., (2014) found no difference in abundance of Talitrus saltator between Greek beaches that frequently hosts small scale beach-parties with lights at night and those that were not used in this way.

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 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.  The biotope (based on the biological assemblage) is therefore 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

No specific evidence for Echinogammarus incertae sedis planicrurus was found. Intertidal amphipods such as talitrids have eyes (eyelessness is more commonly associated with deep-sea species, Thurston & Bett, 1993). Visual perception by talitrids is used to detect predators and orientate using landscape and other cues (Hartwick, 1976). it is likely that the amphipods could detect movement and would react by burrowing or escaping. This disturbance may interrupt feeding and other behaviour but may not lead to lethal effects. Biotope resistance based on Echinogammarus incertae sedis planicrurus is assessed as 'High' and resilience as 'High', so that the biotope is assessed as 'Not sensitive'.

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.

Introduction or spread of invasive non-indigenous species

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

Evidence

The sediments characterizing this biotope are coarse, mobile and free-draining, this limits the establishment of marine and coastal invasive non-indigenous species as the habitat conditions are unsuitable for most species, as exemplified by the low species richness characterizing this biotope. Invasion of rivers and freshwaters by invasive non-indigenous amphipods has been documented, but no potential invasive species were identified for the habitat this biotope occurs in. Overall, there is no evidence of this biotope being adversely affected by non-native species. 

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 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).  The amphipod Orchestia gammarellus is host to the parasitic protist Marteilia sp. which has a feminizing effect on populations, with higher rations of females and intersex males in infected, estuarine populations (Ginsburger-Vogel & Desportes, 1979).

No evidence was found for pathogen/parasite outbreaks that may result in mass-mortalities in Echinogammarus incertae sedis planicrurus 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

No species within the biotope are targeted by commercial or recreational fishers or harvesters. 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

The loss of the key characterizing species through unintentional removal would alter the character of the biotope and may lead to reclassification to a similar, species-poor biotope such as LS.LSa.MoSa.BarSa. The ecosystem services such as secondary production and food for higher trophic levels such as birds provided by the amphipods would be lost.

Sensitivity assessment. Biotope resistance to loss of the characterizing species is assessed as ‘Low’ as the burrowing lifestyle and mobility of Echinogammarus incertae sedis planicrurus means that a proportion of the population may escape removal. Resilience is assessed as ‘High’ based on in-situ recovery and migration from adjacent populations: sensitivity is therefore assessed as ‘Low’.