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

Gammarus salinus lives in a variety of locations within the estuarine environment: amongst algae and other vegetation, as well as generally over the sediment surface and beneath stones. Gammarus salinus is a mobile species capable of a rapid escape response and therefore likely to be able to local substratum loss. Nevertheless, a proportion of the population is likely to be removed with the substratum. Therefore, an intolerance assessment of intermediate has been made. Recoverability is likely to be very high (see additional information below.

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

Gammarus salinus lives in a variety of locations within the estuarine environment: amongst algae and other vegetation, as well as generally over the sediment surface and beneath stones. It is a mobile species capable of a rapid escape response (back flip) if disturbed, however in the event of suddenly being smothered by 5 cm of sediment individuals resting on the surface may be killed, particularly so if the materials are viscous or impermeable. Intolerance has been assessed to be intermediate. Recovery has been assessed to be very high owing to the production of an new generation within the year (see additional information below).

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

As an estuarine species Gammarus salinus probably experiences fluctuations in the concentration of suspended sediment, which in the estuarine environment may be measurable in grams per litre (benchmark is mg per litre). Consequently the benchmark increase for the duration of one month is unlikely to affect Gammarus salinus and it has been assessed to be tolerant.

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

As an estuarine species Gammarus salinus probably experiences fluctuations in the concentration of suspended sediment, which in the estuarine environment may be measurable in grams per litre (benchmark is mg per litre). Consequently the benchmark decrease for the duration of one month is unlikely to affect Gammarus salinus and it has been assessed to be tolerant.

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

Desiccation events are unlikely to prove a lethal factor to a species with a rapid escape response and ability to find cover. Consequently, the species is probably sufficiently mobile to avoid prolonged exposure if stranded and intolerance has been assessed to be low. Recovery is likely to be immediate upon finding cover.

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

In the estuarine environment Gammarus salinus may experience regular periods of immersion and emersion. At low tide it probably seeks shelter amongst vegetation, under pebbles / rock or burrows loosely into the surface of the substratum in order to avoid the effects of desiccation. Gammarus salinus is a relatively slow crawler, swimming using the three pairs of pleopods is much faster. However, the speciality of amphipods is the tail-flip, a rapid escape response whereby the abdomen flicks the animal away after the uropods are dug into the ground. Consequently, the species is probably sufficiently mobile to avoid prolonged exposure resulting from an increase in emergence and intolerance has been assessed to be low. Recovery is likely to be immediate upon finding cover.

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

In the estuarine environment Gammarus salinus may experience regular periods of immersion and emersion. An increased period of immersion may favour fish which prey upon Gammarus salinus such as sprats, Sprattus sprattus. However, although normally abundant in the environment, Gammarus salinus was ingested in disproportionately small quantities by other fish, perhaps reflecting its concealment amongst floating weeds and a selection made by larger fish against small (< 1 cm) prey items (Moore & Moore, 1976). Intolerance has been assessed to be low and recoverability likely to be very high (see additional information, below).

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

Spooner (1947) stated that species of Gammarus are relatively indifferent to the nature of the substratum to a remarkable degree, provided that there is some kind of object to provide them with shelter/cover. However, an increase in the water flow rate would increase scour which, over the period of a year (see benchmark) may create the problem of retaining a position in the estuarine environment, against conditions of net seaward transport. Therefore intolerance has been assessed to be high as the population may be washed from the estuary. Recovery and repopulation are likely to occur within a year (see additional information, below).

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

A decrease in water flow rate, in the absence of wave action determining particle grain size, would favour the accretion of finer silts and clays. Such deposition would alter not only the physical properties of the substratum, but also the chemical properties, especially the degree of oxygenation. Spooner (1947) stated that species of Gammarus are relatively indifferent to the nature of the substratum to a remarkable degree, provided that there is some kind of object to provide them with shelter/cover and such changes are unlikely to be of consequence to Gammarus salinus. Therefore, an assessment of tolerant has been made.

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

Gammarus salinus lives in brackish waters and experiences a variety of temperature and salinity changes. Furch (1972) exposed Gammarus salinus to both constant (8 °C, 14 °C & 20 °C) and fluctuating (daily fluctuations between 8 °C to 20 °C) temperatures. The species revealed significant differences in heat resistance, which became apparent within 12 hours. Gammarus salinus was able to endure long term exposure (2 to 4 weeks) to fluctuating temperatures, although fast temperature changes (every hour) were less well tolerated by it than slower temperature fluctuations (2 hours). Intolerance has been assessed to be low, as acute temperature changes may cause additional stress but did not result in mortality. Recovery from rapid fluctuations was apparent within a matter of hours, therefore recovery has been assessed to be immediate. Parasitized specimens may be more intolerant of acute temperature increases.

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

Gammarus salinus lives in brackish waters and experiences a variety of temperature and salinity changes. The distribution of Gammarus salinus extends to the north of the UK, into the Baltic Sea, so the species would probably tolerate a chronic decrease of 2 °C. Acute temperature decreases may cause death of vulnerable individuals, such as those that are parasitized owing to additional stress, and intolerance has been assessed to be intermediate.

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

Gammarus salinus may feed upon macroalgae as well as detritus, which is dependant on light availability for photosynthesis. An increase in turbidity for the duration of a year would reduce light penetration and therefore probably the abundance of macroalgae as a food resource which may consequently affect the species viability. Therefore intolerance to increased turbidity has been assessed to be low. The species is likely to have a very high capacity for recovery (see additional information below).

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

Gammarus salinus is not likely to be directly sensitive to 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

Gammarus salinus normally inhabits relatively well sheltered estuarine environments. It is likely to be washed away as a result of increased wave exposure owing to turbulence displacing it from shelter. The algae on which it feeds may also become detached, reducing its food source. Consequently intolerance has been assessed to be high.

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

Decreased wave exposure is likely to result in changes to the composition of the estuarine substratum e.g., the accretion of finer particulate matter, settling out as a result of reduced turbulence. However, Spooner (1947) considered that species of Gammarus were relatively indifferent to the nature of the substratum to a remarkable degree, provided that they could find cover and it has been assessed as tolerant of a decrease in wave exposure.

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

Gammarus salinus may respond to vibrations caused by noise, but it is unlikely to be directly sensitive to noise 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

Gammarus salinus is unlikely to have the visual acuity to detect the presence of boats, machinery present in its environment, and it has been assessed not to be sensitive to the factor.

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

Gammarus salinus is small, a highly mobile and likely to be able to avoid physical disturbance or to pass through passing fishing gear. Therefore, it has been assessed to be tolerant of physical disturbance.

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

Gammarus salinus is a mobile species and therefore an intolerance assessment for displacement was not considered to be relevant.

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 specifically concerning the effects of synthetic chemicals upon Gammarus salinus was found. However, in the closely related Gammarus duebeni, reproductive behaviour in the male is evoked by its detection of a chemical cue from the female. The cue is perceived by receptors on the second antennae and its function is to synchronize mating with the suitable phase of ecdysis in the female. Low concentration of the surfactant TWEEN 80 were shown to interfere with the reception of the females chemical cues, resulting in a decrease in mating success (Lyes, 1979).
Lawrence & Poulter (2001) examined the effect of pentachlorophenol (PCP) and benzo[a]pyrene (B[a]P) on the embryogenesis, and swimming stamina of Chaetogammarus marinus against a pump driven head of water. Swimming stamina was significantly impaired at a concentration of 40 µg PCP/l and 20µg B[a]P/l, whilst development of in vitro cultured embryos was significantly impaired by 20 µg /l of both PCP and B[a]P.
intolerance has been assessed to be low owing to evidence of sub-lethal effects and reduced reproductive potential. Gammarus salinus is likely to have a very high capacity for recovery (see additional information below), assuming deterioration of the contaminants.

Heavy metal contamination

Evidence

• No information specifically concerning the effects of heavy metals upon Gammarus salinus was found. However, a closely related species Gammarus zaddachi occurred in the brackish water upper reaches of Restronguet Creek, Fal Estuary, Cornwall, and over the creeks entire length there was a continuous population of gammarids, which was composed of several species of a typical succession (Bryan & Gibbs, 1983). Water entering Restronguet Creek from the Carnon River was acidic (pH 3.8) and contained high concentrations of soluble Fe (18500µg/l), Zn (12030µg/l), Mn (2974µg/l) and Cu (474µg/l) (Table 1, Site 1, Bryan & Gibbs, 1983). However, there was no further information concerning specific effects of such heavy metal concentrations on the gammarids, except to say that the flora and fauna in general in Restronguet Creek was less obviously affected than might be predicted from toxicity data in the literature. Possible reasons being development of metal-tolerant strains and/or the ability of species to migrate into other less contaminated areas of the Fal System (Bryan & Gibbs, 1983).
• 
  Lawrence & Poulter (2001) examined the effect of copper on the embryogenesis and swimming stamina of Chaetogammarus marinus against a pump driven head of water. Swimming stamina was significantly impaired at a concentration of 15 µg Cu/l, whilst development of in vitro cultured embryos was significantly impaired by 20 µg Cu/l. Copper exposure extended the period of embryogenesis by 4 to 8 days and specific stages in the embryos' development were affected. These two assays were also responsive at environmental concentrations periodically experienced at some locations on the Humber Estuary, UK (Lawrence & Poulter, 2001).
• 
  Ritz (1980) examined the tolerance of two intertidal amphipods, Gammarus duebeni and Marinogammarus marinus to copper under static conditions. For Marinogammarus marinus the LT₅₀ varied from 106 hours in 0.04 ppm Cu, to 3 hours in 4 ppm Cu. Mortality in 0.04 ppm Cu was not significantly different to that in the control. For Gammarus duebeni the corresponding LT₅₀ values were > 5 days at 0.04 ppm Cu and 3 hours at 4 ppm Cu. At concentrations of 0.04 ppm and below, the copper was not acutely toxic to Gammarus duebeni.

intolerance has been assessed to be low owing to evidence of only sub-lethal effects of heavy metals and influence upon embryogenesis in another closely related species. Gammarus salinus is likely to have a very high capacity for recovery (see additional information below), assuming deterioration of the contaminants.

Hydrocarbon contamination

Evidence

Amphipods have been reported to be sensitive to oil (Suchanek, 1993).

• Ponat (1975) observed the narcotic effect of crude oil on Gammarus salinus, which reduced the species oxygen consumption to 40 % of normal levels.
• Lindén (1976) also observed narcosis in Gammarus oceanicus, a species related to Gammarus salinus, exposed to concentrations of oil between 5 and 20 mg/l, which caused an initial period of hectic swimming and then deterioration in crawling ability. Furthermore sub-lethal concentrations of crude oil (1-40µg /l) proved to be responsible for a reduction in the numbers of sexually mature adults of Gammarus oceanicus entering precopula, a requirement of successful fertilization (Lindén, 1976b).
• Penetration of the substratum by oil released from the Amoco Cadiz translated into massive mortality of amphipods of the genus Ampelisca in the fine sand of the Bay of Morlaix, north-west Brittany, France (Cabioch et al., 1978).

intolerance of Gammarus salinus to hydrocarbon contamination has been assessed to be high. Despite a very high capacity for recovery (see additional information below), recovery from hydrocarbon contamination has been assessed to be high rather than very high owing to the probable persistence of oil in sediments and the likelihood that juveniles are especially susceptible.

Radionuclide contamination

Evidence

Insufficient
information.

Changes in nutrient levels

Evidence

Gammarus salinus is a both a detritivore and herbivore, consequently it may benefit form nutrient enrichment that stimulates the productivity of phytoplankton and macroalgae. Anger (1977) listed Gammarus salinus as an indicator species for slight organic pollution. Furthermore, Gammarus salinus has demonstrated a negative rheotaxic response to lethal and sublethal concentrations of oxygen (see oxygenation) which may result as a consequence of eutrophication. Therefore it has been assessed to be tolerant* to nutrient enrichment.

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

Gammarus salinus is a euryhaline species relatively tolerant of salinities as low as 2 psu and as high as 30 psu, but it is most abundant at 10 psu. It is likely that the species would experience some physiological stress following an acute increase in salinity (see decrease in salinity below), intolerance has therefore been assessed to be low and, as an euryhaline species, it is likely to recover relatively rapidly.

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

Gammarus salinus is a euryhaline species relatively tolerant of salinities as low as 2 psu and as high as 30 psu, but it is most abundant at 10 psu. Bulnheim (1984) recorded the respiratory response of Gammarus salinus in response to an acute salinity change, from 30 psu to 10 psu, respiration rate moderately increased after an initial shock like response and initially specimens were quiescent as they acclimated to the decreased salinity but recovered within 24 hours. Intolerance has therefore been assessed to be low and recovery immediate.

Changes in oxygenation

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

Evidence

Gammarids are occasionally found in locations with reduced O₂ tensions, especially on soft substratum, in stagnant pools and in polluted waters. In deeper waters oxygen deficiency may be accompanied by the formation of hydrogen sulphide. Bulnheim (1984) examined the survival rates of five gammarid species held in brackish water with poor oxygenation. The LT ₅₀ for Gammarus salinus held at 15 °C, 10 psu with a depleted oxygen level of 0.5 ml O₂/l was 6.5 hours, 100% mortality occurred after 15 hours. Gammarus salinus being more tolerant than Gammarus locusta and Gammarus oceanicus. Gammarus salinus had an LT₅₀ of 4 hours in brackish-water (10 psu) with oxygen depletion in the presence of hydrogen sulphide (< 0.2 ml O₂/l + 50 mg Na₂S.9H₂O/l) at 15 °C . However, Vobis (1973) used an experimental vessel to observe the behaviour of gammarids in various water current speeds and oxygen concentrations. In adequately oxygenated waters, Gammarus salinus demonstrated a moderate positive rheotaxis (swimming into the current). Lethal and sublethal oxygen concentrations, however, led to negative rheotaxis (swimming away from the current). Oxygen deficiency caused Gammarus salinus to swim downstream at 2.5 mg O₂ per litre. An intolerance assessment of low has been made, as the species can avoid the factor. The species is likely to repopulate areas as soon as the oxygen concentration of the water becomes optimal and recovery has been assessed to be immediate.

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

Gammarus salinus, Gammarus zaddachi and Gammarus oceanicus were found to be important host species for the transmission of parasites (Voigt, 1991). Larval stages of 4 fish parasites (1 Nematoda, 2 Acanthocephala and 1 Digena) as well as larval stages of 4 bird parasites (1 Nematoda, 1 Acanthocephala, 1 Digena and 1 Cestoda) were found. However, there was insufficient information concerning the effect that such parasitization may have on the species viability.

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

No information concerning non-native species that might affect the abundance or survival of Gammarus salinus was found.

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

Gammarus salinus is not a species targeted for extraction.

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

No information concerning the extraction of other species that might affect the abundance or survival of Gammarus salinus was found.