The Marine Life Information Network

Substratum loss

Benchmark. All of the substratum occupied by the species or biotope under consideration is removed. A single event is assumed for sensitivity assessment. Once the activity or event has stopped (or between regular events) suitable substratum remains or is deposited. Species or community recovery assumes that the substratum within the habitat preferences of the original species or community is present. Further details

Evidence

Pisidia longicornis occurs on a variety of substrata especially in the subtidal. Although at least some individuals will be destroyed by the removal of substratum, displaced individuals are likely to find alternative homes. The crabs are mobile and have a planktonic larva so that recolonization/recovery is likely to be fairly rapid.

Smothering

Benchmark. All of the population of a species or an area of a biotope is smothered by sediment to a depth of 5 cm above the substratum for one month. Impermeable materials, such as concrete, oil, or tar, are likely to have a greater effect. Further details.

Evidence

Pisidia longicornis, being mobile, may escape from smothering events but siltation may remove suitable habitats by clogging underboulders and undergrowth. The crabs are mobile and have a planktonic larva so that recolonization/recovery is likely to be fairly rapid.

Increase in suspended sediment

Benchmark. An arbitrary short-term, acute change in background suspended sediment concentration e.g., a change of 100 mg/l for one month. The resultant light attenuation effects are addressed under turbidity, and the effects of rapid settling out of suspended sediment are addressed under smothering. Further details

Evidence

Pisidia longicornis most likely feeds as a scavenger and active carnivore so that increase in levels of suspended sediment are unlikely to affect it. However, settlement of suspended silt is addressed in 'Smothering'.

Decrease in suspended sediment

Benchmark. An arbitrary short-term, acute change in background suspended sediment concentration e.g., a change of 100 mg/l for one month. The resultant light attenuation effects are addressed under turbidity, and the effects of rapid settling out of suspended sediment are addressed under smothering. Further details

Evidence

Pisidia longicornis most likely feeds as a scavenger and active carnivore so that decrease in levels of suspended sediment are unlikely to affect it.

Desiccation

1. A normally subtidal, demersal or pelagic species including intertidal migratory or under-boulder species is continuously exposed to air and sunshine for one hour.
2. A normally intertidal species or community is exposed to a change in desiccation equivalent to a change in position of one vertical biological zone on the shore, e.g., from upper eulittoral to the mid eulittoral or from sublittoral fringe to lower eulittoral for a period of one year. Further details.

Evidence

Pisidia longicornis lives in habitats that are protected from desiccation and would most likely, because of its mobility, be able to escape desiccation situations such as boulder turning. However, if exposure to air occurs, desiccation effects are likely to be severe. The crabs are mobile and have a planktonic larva so that recolonization/recovery is likely to be fairly rapid.

Increase in emergence regime

Benchmark. A one hour change in the time covered or not covered by the sea for a period of one year. Further details

Evidence

Pisidia longicornis lives in shaded damp habitats on the mid to lower shore. If emergence regime changes so that crabs are exposed for longer to dry conditions, the vertical extent of habitat suitable for the crab is likely to be reduced although individual crabs will survive by moving further downshore. The crabs are mobile and have a planktonic larva so that recolonization/recovery is likely to be fairly rapid.

Decrease in emergence regime

Benchmark. A one hour change in the time covered or not covered by the sea for a period of one year. Further details

Evidence

Pisidia longicornis is a species that lives in damp places and fully submerged habitats so that decrease in emergence will favour the species.

Increase in water flow rate

A change of two categories in water flow rate (view glossary) for 1 year, for example, from moderately strong (1-3 knots) to very weak (negligible). Further details

Evidence

Pisidia longicornis lives in habitats where water flow rate may be from very strong to weak. However, as a cryptic species protected by bryozoan turf, kelp holdfasts etc in the sublittoral, it is unlikely to be affected by 'wash out' which might however occur from under boulders. The crabs are mobile and have a planktonic larva so that recolonization/recovery is likely to be fairly rapid.

Decrease in water flow rate

A change of two categories in water flow rate (view glossary) for 1 year, for example, from moderately strong (1-3 knots) to very weak (negligible). Further details

Evidence

The communities in which Pisidia longicornis live are particularly well developed in areas subject to strong tidal flow or strong wave action. In the absence of strong wave action, decrease in water flow rate will lead to siltation of habitats and reduction of the bryozoan turf that Pisidia longicornis favours. A decline in abundance would therefore be expected. The crabs are mobile and have a planktonic larva so that recolonization/recovery is likely to be fairly rapid.

Increase in temperature

1. A short-term, acute change in temperature; e.g., a 5°C change in the temperature range for three consecutive days. This definition includes ‘short-term’ thermal discharges.
2. A long-term, chronic change in temperature; e.g. a 2°C change in the temperature range for a year. This definition includes ‘long term’ thermal discharges.

For intertidal species or communities, the range of temperatures includes the air temperature regime for that species or community. Further details

Evidence

Pisidia longicornis occurs in a wide range of temperature regimes from Norway to Angola and it is not therefore expected that crabs would be adversely affected by increase in temperature at the level of the benchmark.

Decrease in temperature

1. A short-term, acute change in temperature; e.g., a 5°C change in the temperature range for three consecutive days. This definition includes ‘short-term’ thermal discharges.
2. A long-term, chronic change in temperature; e.g. a 2°C change in the temperature range for a year. This definition includes ‘long term’ thermal discharges.

For intertidal species or communities, the range of temperatures includes the air temperature regime for that species or community. Further details

Evidence

Long-clawed porcelain crabs were adversely affected by the 1962-63 winter in Britain. Crisp (1964) records that many hundreds were found dead on the strandline at Oxwich, south Wales. In other locations, they were not found on the shore (although could have migrated offshore). Overall, it seems that some mortality is likely and an intolerance of Intermediate is suggested. The crabs are mobile and have a planktonic larva so that recolonization/recovery is likely to be fairly rapid.

Increase in turbidity

1. A short-term, acute change; e.g., two categories of the water clarity scale (see glossary) for one month, such as from medium to extreme turbidity.
2. A long-term, chronic change; e.g., one category of the water clarity scale (see glossary) for one year, such as from low to medium turbidity. Further details

Evidence

Pisidia longicornis is a scavenger and is only likely to be adversely affected by increased turbidity through visual impairment. The crabs are mobile and have a planktonic larva so that recolonization/recovery is likely to be fairly rapid.

Decrease in turbidity

1. A short-term, acute change; e.g., two categories of the water clarity scale (see glossary) for one month, such as from medium to extreme turbidity.
2. A long-term, chronic change; e.g., one category of the water clarity scale (see glossary) for one year, such as from low to medium turbidity. Further details

Evidence

Pisidia longicornis is a scavenger and is unlikely to be adversely affected by decreased turbidity.

Increase in wave exposure

A change of two ranks on the wave exposure scale (view glossary) e.g., from Exposed to Extremely exposed for a period of one year. Further details

Evidence

Pisidia longicornis lives in locations where it could be displaced by strong water movement. The crabs are mobile and have a planktonic larva so that recolonization/recovery is likely to be fairly rapid.

Decrease in wave exposure

A change of two ranks on the wave exposure scale (view glossary) e.g., from Exposed to Extremely exposed for a period of one year. Further details

Evidence

Pisidia longicornis lives underboulders, in kelps holdfasts and amongst bryozoan turfs especially. A decrease in wave exposure may allow silt to settle thus removing suitable habitats by clogging underboulders and undergrowth. The crabs are mobile and have a planktonic larva so that recolonization/recovery is likely to be fairly rapid.

Noise

1. Underwater noise levels e.g., the regular passing of a 30-metre trawler at 100 metres or a working cutter-suction transfer dredge at 100 metres for one month during important feeding or breeding periods.
2. Atmospheric noise levels e.g., the regular passing of a Boeing 737 passenger jet 300 metres overhead for one month during important feeding or breeding periods. Further details

Evidence

Pisidia longicornis is unlikely to react to noise as it has no appropriate organs. It will most likely react to vibrations resulting from noise but is probably tolerant at the benchmark level.

Visual presence

Benchmark. The continuous presence for one month of moving objects not naturally found in the marine environment (e.g., boats, machinery, and humans) within the visual envelope of the species or community under consideration. Further details

Evidence

Crabs scuttle away when boulders are overturned - most likely as a response to increased light levels but also, since they have eyes, visual presence. The crabs are mobile so that recolonization/recovery is likely to be very rapid.

Abrasion & physical disturbance

Benchmark. Force equivalent to a standard scallop dredge landing on or being dragged across the organism. A single event is assumed for assessment. This factor includes mechanical interference, crushing, physical blows against, or rubbing and erosion of the organism or habitat of interest. Where trampling is relevant, the evidence and trampling intensity will be reported in the rationale. Further details.

Evidence

The crabs are easily crushed by abrasion by mobile cobbles and larger substrata or by mooring chains. The crabs are mobile and have a planktonic larva so that recolonization/recovery is likely to be fairly rapid.

Displacement

Benchmark. Removal of the organism from the substratum and displacement from its original position onto a suitable substratum. A single event is assumed for assessment. Further details

Evidence

Displacement is unlikely to adversely affect Pisidia longicornis unless it is trapped in a new unsuitable location. The species can move to a suitable area.

Synthetic compound contamination

Sensitivity is assessed against the available evidence for the effects of contaminants on the species (or closely related species at low confidence) or community of interest. For example:

• evidence of mass mortality of a population of the species or community of interest (either short or long term) in response to a contaminant will be ranked as high sensitivity;
• evidence of reduced abundance, or extent of a population of the species or community of interest (either short or long term) in response to a contaminant will be ranked as intermediate sensitivity;
• evidence of sub-lethal effects or reduced reproductive potential of a population of the species or community of interest will be assessed as low sensitivity.

The evidence used is stated in the rationale. Where the assessment can be based on a known activity then this is stated. The tolerance to contaminants of species of interest will be included in the rationale when available; together with relevant supporting material. Further details.

Evidence

No information has been found specifically on Pisidia longicornis but crustaceans in general are fairly tolerant. Bryan & Gibbs (1991) report that crabs appear to be relatively resistant to TBT although some deformity of regenerated limbs has been observed. In the early 1960's in Washington, experimental application of a broad range of pesticides was tested for use on shrimp-infested oyster grounds identified carbaryl (1-napthol n-methyl carbamate; sold under the trade name Sevin) to be an effective method to control burrowing shrimp (Feldman et al., 2000). Carbaryl, a non-persistent organocarbamate pesticide that is extremely toxic to arthropods, was applied at 9kg/ha to remove shrimps from oyster grounds. In view of the equivocal results from different studies and with different chemicals, an intolerance of intermediate is suggested with a very low confidence. The crabs are mobile and have a planktonic larva so that recolonization/recovery is likely to be fairly rapid.

Heavy metal contamination

Evidence

No information has been found specifically on Pisidia longicornis but crustaceans in general are fairly tolerant. Crompton (1997) reports that the concentrations above which mortality of crustaceans can occur is 0.01-0.1mg/l for mercury, copper and cadmium, 0.1-1mg/l for zinc, arsenic and nickel and 1-10mg/l for lead and chromium. Crustaceans are generally regarded as being more intolerant of cadmium than other groups (McLusky, 1986).The crabs are mobile and have a planktonic larva so that recolonization/recovery is likely to be fairly rapid.

Hydrocarbon contamination

Evidence

No information has been found specifically on Pisidia longicornis but crustaceans in general are fairly tolerant. The crabs are mobile and have a planktonic larva so that recolonization/recovery is likely to be fairly rapid.

Radionuclide contamination

Evidence

No information has been found for radionuclides adversely affecting crustaceans.

Changes in nutrient levels

Evidence

No information has been found for nutrients adversely affecting crustaceans.

Increase in salinity

1. A short-term, acute change; e.g., a change of two categories from the MNCR salinity scale for one week (view glossary) such as from full to reduced.
2. A long-term, chronic change; e.g., a change of one category from the MNCR salinity scale for one year (view glossary) such as from reduced to low. Further details.

Evidence

Long-clawed porcelain crabs are apparently not recorded in low salinity conditions but do occur in the lower reaches of estuaries suggesting that they require full or variable salinity. Mortality may therefore occur in events where salinity falls significantly. The crabs are mobile and have a planktonic larva so that recolonization/recovery is likely to be fairly rapid.

Decrease in salinity

1. A short-term, acute change; e.g., a change of two categories from the MNCR salinity scale for one week (view glossary) such as from full to reduced.
2. A long-term, chronic change; e.g., a change of one category from the MNCR salinity scale for one year (view glossary) such as from reduced to low. Further details.

Evidence

Long-clawed porcelain crabs are apparently not recorded in low salinity conditions but do occur in the lower reaches of estuaries suggesting that they require full or variable salinity. A reduction in salinity, especially if it occurs in already estuarine conditions, is likely therefore to have a significant adverse effect. The crabs are mobile and have a planktonic larva so that recolonization/recovery is likely to be fairly rapid.

Changes in oxygenation

Benchmark.  Exposure to a dissolved oxygen concentration of 2 mg/l for one week. Further details.

Evidence

The crabs live in areas which are well oxygenated so that decrease in oxygen levels below ambient may be adverse. The crabs are mobile and have a planktonic larva so that recolonization/recovery is likely to be fairly rapid.

Introduction of microbial pathogens/parasites

Benchmark. Sensitivity can only be assessed relative to a known, named disease, likely to cause partial loss of a species population or community. Further details.

Evidence

Insufficient
information

Introduction of non-native species

Sensitivity assessed against the likely effect of the introduction of alien or non-native species in Britain or Ireland. Further details.

Evidence

Insufficient
information

Extraction of this species

Benchmark. Extraction removes 50% of the species or community from the area under consideration. Sensitivity will be assessed as 'intermediate'. The habitat remains intact or recovers rapidly. Any effects of the extraction process on the habitat itself are addressed under other factors, e.g. displacement, abrasion and physical disturbance, and substratum loss. Further details.

Evidence

Extraction of this species is not known to occur. The crabs are mobile and have a planktonic larva so that recolonization/recovery is likely to be fairly rapid.

Extraction of other species

Benchmark. A species that is a required host or prey for the species under consideration (and assuming that no alternative host exists) or a keystone species in a biotope is removed. Any effects of the extraction process on the habitat itself are addressed under other factors, e.g. displacement, abrasion and physical disturbance, and substratum loss. Further details.

Evidence

Insufficient
information