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

Neomysis integer is a free-swimming mysid shrimp, which may rest on the surface of the substratum, but does not live within it. Therefore it has been assessed to be tolerant of substratum loss.

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

Neomysis integer is a free-swimming mysid shrimp, which may rest on the surface of the substratum, but does not live within it and it is sufficiently mobile to avoid the deposition of smothering materials. Therefore Neomysis integer has been assessed to be not sensitive to smothering at the benchmark level.

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

Neomysis integer is omnivorous and employs one or both of two distinct methods of feeding. It may filter phytoplankton and suspended detrital material or feed as an active carnivore on zooplankton or benthic invertebrates. Consequently, increased concentrations of suspended matter in the water column may be indicative of an enhanced food supply and the species has been assessed not 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

Neomysis integer is omnivorous and employs one or both of two distinct methods of feeding. It may filter phytoplankton and suspended detrital material or feed as an active carnivore on zooplankton or benthic invertebrates. A reduction in the concentration of suspended matter in the water column may reduce the species viability as a consequence of reduced food supply. Therefore intolerance has been assessed to be low. On return to prior conditions, recovery is likely to be immediate as the shrimp commences optimal feeding.

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

Neomysis integer is likely to be very intolerant of continual exposure to air and sunshine for one hour and any individuals washed ashore would undoubtedly die. But the estuarine environment its endogenous swimming rhythm, coupled with a rheotaxic behaviour serves to prevent stranding on the substratum at low tide (Hough & Naylor, 1992) (see general adult biology). Therefore, dessication is probably not relevant.

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

Neomysis integer is a free-swimming mysid shrimp, which is sufficiently mobile to avoid a change in the emergence regime in its estuarine environment. Therefore an intolerance assessment was not considered to be relevant.

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

Neomysis integer is a free-swimming mysid shrimp, which is sufficiently mobile to avoid a change in the emergence regime in its estuarine environment. Therefore an intolerance assessment was not considered to be relevant.

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

In the field, where flows in the open channel over the tidal cycle were greater than that which Neomysis integer can swim against or maintain position, Lawrie et al., (1999) observed Neomysis integer to aggregate in low-flow areas, such as in the lee of rocks and macroalgal clumps, in the shallowest edge waters and at the 'boundary layer' (sediment-water interface), where water flow rates were not in excess of 10 cm/sec (0.2 of a knot). Intolerance of Neomysis integer to the benchmark increase in water flow rate has been assessed to be intermediate. The species would be exposed to flow rates of between 0.5-1.5 m/sec and in the absence of objects behind which to shelter the species would be washed rapidly seawards. Some individuals may die following exposure to fully saline conditions (see increase in salinity) but the abundance of the population is more likely to be reduced as other coastal currents disperse the population and fewer may be washed back into the estuary on the flood tide. On return to prior conditions the species is likely to have a very high capacity for recovery (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

The benchmark decrease in water flow rate would create areas where water flow was negligible and the species may be better able to maintain position in open water, potentially enabling enhanced periods of feeding with reduced risk of displacement from the estuarine environment. 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

Environmental temperature exerts an influence on many of the physiological processes of mysid shrimps (Mauchline, 1980). However, the tolerance of mysid shrimps to changes in environmental temperatures varies between species and, to a lesser extent, between populations of the same species in different environments (Mauchline, 1980). Very little information concerning environmental temperatures and the distribution of mysid shrimps is available. However, the distribution of Neomysis integer extends to the south of the UK, along the Atlantic coast of Spain, so the species may be able to tolerate a chronic change of 2 °C. Kinne (1955) found that juveniles of Neomysis integer had a different tolerance to temperature changes than adults. Kuhlman (1984) also found that over-wintering and summer generations of Neomysis integer demonstrated distinct differences to increasing temperature, the upper tolerance of the winter generation being 10-12 °C in comparison to 20-25 °C for the summer generation. Consequently, an acute increase in temperature may be more damaging to the population during the spring, when the over wintering population commences breeding, than at other times and intolerance has been assessed to be intermediate. Following a decrease in population, Neomysis integer is likely to recover within a few weeks or at most six months following summer recruitment and probable migration between suitable habitats, therefore recoverability has been assessed to be very high.

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

The distribution of Neomysis integer extends to the north of the UK, along the Arctic coast of Norway, so the species may be able to tolerate a chronic change of 2 °C. Acute decreases in temperature may cause death of some vulnerable individuals, such as those that are parasitized owing to additional stress and intolerance has therefore been assessed to be intermediate. Following a decrease in population, Neomysis integer is likely to recover within a few weeks or at most six months following summer recruitment and probable migration between suitable habitats, therefore recoverability has been assessed to be very high.

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

In general, mysids are attracted to weak sources of light, but avoid bright light (Mauchline, 1980). Bright light often inhibits swimming activity. Normal diurnal light levels are inhibitory and produce a negatively phototactic response in most species and the 24 hour cycle of change in ambient light intensity is the dominant factor controlling the diel vertical migration of mysids. The nocturnal period of darkness stimulates the upward migration into the pelagic zone (Beeton, 1960; McNaught & Hasler, 1966; Heubach, 1969; Teraguchi et al., 1975; cited in Mauchline, 1980). Increased turbidity may serve to extend the nocturnal vertical migration period of Neomysis integer during dawn and dusk, as turbidity inhibits light penetration. As diel migration is a normal behavioural pattern of Neomysis integer an increase in turbidity is unlikely to affect the species. Furthermore, increased turbidity may hinder predatory fish which feed upon Neomysis integer.

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

In general, mysids are attracted to weak sources of light, but avoid bright light (Mauchline, 1980). Bright light often inhibits swimming activity. Normal diurnal light levels are inhibitory and produce a negatively phototactic response in most species and the 24 hour cycle of change in ambient light intensity is the dominant factor controlling the diel vertical migration of mysids. The nocturnal period of darkness stimulates the upward migration into the pelagic zone (Beeton, 1960; McNaught & Hasler, 1966; Heubach, 1969; Teraguchi et al., 1975; cited in Mauchline, 1980). Decreased turbidity may serve to reduce the extent of the nocturnal vertical migration of Neomysis integer, as light penetration of the water column increases, and possibly limit feeding. Furthermore, fish may exploit populations of Neomysis integer more effectively as Neomysis integer probably becomes more easily distinguishable. Intolerance has been assessed to be low and on return to prior conditions recovery is likely to be very high (see additional information below).

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

Wave action in the littoral region affects the distribution of many intertidal species and for mysids in particular it tends to depress their vertical range on the shore, they move offshore into deeper water in order to avoid the effects of breaking waves (Mauchline, 1980). Neomysis integer avoids water flow rates against which it cannot maintain position by sheltering in the lee of rock, macroalgal clumps and in the 'boundary layer' (see increased water flow rate). Increased wave exposure would increase the turbulence of water flow around objects used for shelter and may displace the object. Furthermore, mysids such as Neomysis integer demonstrate rheotaxis (orientate in flowing water, facing into the current) and such behaviour may become energetically exhausting if caught in the wash and back-wash of waves. Intolerance has therefore been assessed to be high. Recovery, following loss of the population is likely to be very high (see additional information, below).

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

The estuarine environment inhabited by Neomysis integer is typically very/extremely wave sheltered and an assessment for a decrease in wave exposure was not considered relevant.

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

Neomysis integer 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

Neomysis integer 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

Neomysis integer is a free-swimming mysid shrimp and not likely to be damaged by a passing scallop dredge as it will probably avoid its effects. (see benchmark). Therefore, an intolerance assessment was not considered to be relevant.

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

Neomysis integer is a free-swimming mysid shrimp and therefore cannot be physically displaced from the substratum. An intolerance assessment was considered not 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

Several synthetic chemicals have been reported to have a toxic effect on Neomysis integer:

• Davies et al., (1997) investigated the acute toxicity of Ivermectin (22, 23-dihydroavermectin B1), a proposed chemotherapeutant for the treatment of farmed salmon infested with sea lice, to Neomysis integer. The 96 hour LC₅₀ of Ivermectin to Neomysis integer was 70 ng/l , with 95% confidence limits of 44 ng/l and 96 ng /l. However, in assessing the potential risk to the marine environment from dissolved Ivermectin from use on fish farms, results indicated that the ratios of the 'Predicted Environmental Concentration' to the 'Predicted No Effect Concentrations' (PEC/PNEC) were small, and the authors suggested that direct toxic effects are unlikely.
• Following 7-day exposure to 0.038 µg chlorpyrifos/l, an organophosphate pesticide, Neomysis integer became hyperactive and more swam forward into a slow current (3 cm m^-1) than control mysids (Roast et al., 2000b). However despite the hyperactivity, chlorpyrifos-exposed Neomysis integer were unable to swim faster than 15 cm m^-1, whereas control specimens were able to swim faster than 18 cm m^-1. In addition to changes in swimming behaviour, fewer pesticide exposed specimens were unable to maintain a position in the annular flume test tank, in comparison with control specimens, and 'swam' in higher current velocities (> 18 cm s^-1), a behaviour which is inconsistent with that in the field. Lawrie et al., (1999) observed Neomysis integer to aggregate in low-flow areas, such as in the lee of rocks, macroalgal clumps and in the shallowest edge waters, where water flow rates were not in excess of 10 cm s^-1. Roast et al., (2000b) suggested that such disruption to the swimming behaviour of Neomysis integer would reduce its ability to maintain position in the natural estuarine environment and populations would probably be lost. Furthermore, the swimming behaviour of Neomysis integer was affected at a pesticide concentration lower than the seven day LC₅₀ concentration of 0.084 µg chlorpyrifos per litre.

intolerance has been assessed to be intermediate. Sub-lethal effects (disruption of swimming) are experienced at low concentrations but are likely to cause the loss or reduce the abundance of estuarine populations owing to the inability of Neomysis integer to maintain position following contaminant exposure. The species is likely to have a very high capacity for recovery (see additional information, below) assuming the decay of the synthetic contaminant.

Heavy metal contamination

Evidence

Roast et al., (2000a) examined the effects of cadmium (Cd) on the swimming behaviour of Neomysis integer. Mysid shrimps such as Neomysis integer, maintain their optimum position in their habitat independent of the forces of river flow and tides; therefore any disruption of swimming behaviour will have significant implications for their survival and position maintenance (Roast et al., 2000a). Following 7 day exposure cadmium, swimming behaviour (ability and orientation) in Neomysis integer was disrupted at 0.5 µg Cd _(aq)²⁺ per litre, a significantly lower cadmium concentration than that causing mortality (7 day LC₅₀ of 2.58 µg Cd _(aq)²⁺ per litre).
Furthermore, toxicity of cadmium to Neomysis integer also varies with salinity. Wildgust & Jones (1998) found that mortalities resulting from free cadmium ion exposure were greater at salinities of 28 and 12 psu than at 20 psu. Wildgust & Jones (1998) thought that the reduction in toxicity of cadmium at a salinity of 20 psu was attributable to an interaction between the cadmium ion and some physiologically active mechanism of Neomysis integer. As the isosmotic point of Neomysis integer (19 psu) is close to 20 psu, the authors interpreted the results to implicate osmoregulation in mediating the uptake, and hence the toxicity, of cadmium to this euryhaline species.
intolerance has been assessed to be intermediate. Sub-lethal effects (disruption of swimming) are experienced at low concentrations but are likely to cause the loss or reduce the abundance of estuarine populations owing to the inability of Neomysis integer to maintain position following heavy metal exposure. Neomysis integer is likely to have a very high capacity for recovery (see additional information, below) assuming the loss of the heavy metal from the environment.

Hydrocarbon contamination

Evidence

Following the sinking of the tanker 'Sefir' during February, 1981, in the Baltic Sea, extreme mortality of littoral fauna, including mysids, was observed after the light fuel oil had washed ashore (Lindén et al., 1983). Laughlin & Linden (1983) exposed Neomysis integer to water-soluble fractions (WSF) of light fuel oil under two different regimes. The first, a chronic exposure scheme, employed concentrations of between 200-500 ng WSF per litre and lasted two weeks. The second, acute exposure, employed concentrations of between 200 and 1000 µg WSF per litre, concentrations that the authors thought representative of oil escaping from a sunken ship or in the vicinity of a spill, especially in sheltered conditions. During the acute exposures, physiological parameters of oxygen consumption, ammonium excretion rate and oxygen : nitrogen ratios were calculated. Exposure of Neomysis integer to WSF oil at concentrations between 200-1000 µg per litre produced increases in oxygen consumption and decreases in ammonia excretion, which were strongly influenced by temperature. Oil exposure had greatest effect on the species at higher temperature, especially 21.5 °C. In contrast, changes in the physiological parameters did not occur to such an extent during the chronic exposure, Laughlin & Linden (1983) considered that the oil doses were probably too low. Furthermore, Laughlin & Linden (1983) suspected that during the chronic exposures, increased temperature alone exerted an effect on Neomysis integer (mortality at time of moults) and the chronic effects of WSF were not measurable. However, in contrast, at temperature < 10 °C, the WSF did qualitatively affect the mysid shrimp. Intolerance has been assessed to be intermediate as some mortality arising from hydrocarbon exposure was reported in the field, and that the species may experience sub-lethal stress in physiological parameters. Neomysis integer is likely to have a very high capability for recovery following degradation of the oil in the environment (see additional information below).

Radionuclide contamination

Evidence

Insufficient
information.

Changes in nutrient levels

Evidence

Neomysis integer is normally resident in estuarine and lagoon environments with comparatively higher nutrient concentrations than that of the open coast. Nutrient enrichment that stimulates phytoplankton productivity may benefit Neomysis integer, as it is omnivorous and suspension feeds on both phytoplankton and suspended detrital material. Furthermore, Neomysis integer is sufficiently mobile to avoid inhospitable conditions that may result from eutrophication, and therefore it has been assessed to be tolerant*.

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

Neomysis integer is a euryhaline species which typically occurs in brackish water habitats, and occasionally in freshwater habitats, but more rarely in fully marine conditions. In laboratory experiments, Kuhlman (1984) found the upper salinity tolerance of Neomysis integer to be between 20 psu to 25 psu, and mortality increased significantly at 30 psu. Under normal circumstances the species is typically found in waters of up to 20 psu, both the acute and chronic benchmark increases in salinity would expose Neomysis integer to a salinity to which it is intolerant. Therefore intolerance has been assessed to be high.

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

Neomysis integer is a euryhaline species which typically occurs in brackish water habitats, and occasionally in freshwater habitats which were once connected to the sea. For instance, Neomysis integer adapted successfully to the transition from brackish lagoon to freshwater lagoon in the case of Loch Mor Barvas, Isle of Lewis, Scotland (Barnes, 1994). In laboratory experiments, Kuhlman (1984) reported the lowest salinity tolerance of the species to be lower than 5 psu, and in other texts it is suggested that Neomysis integer tolerates salinities down to 0.5 psu (Koepcke & Kausch, 1996; Barnes, 1994). Therefore Neomysis integer has been assessed as not sensitive at the benchmark leve decrease in salinity.

Changes in oxygenation

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

Evidence

In laboratory experiments, Kuhlman (1984), lowered the oxygen saturation of seawater in which specimens of Neomysis integer were held over two days, to 20 % (approximately 6.5 mg /O₂ per litre with no negative influence on behaviour or survival. A narrow sublethal and lethal threshold was determined between 20% (6.5 mg /O₂ per litre) and 13 % (4.23 mg/O₂ per litre) saturation (Kuhlman, 1984). However, the species is sufficiently mobile to avoid sub optimal concentrations of oxygen and therefore an intolerance assessment of not relevant has been made.

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

Astthorsson (1980) found specimens of Neomysis integer collected from the Ythan Estuary, Scotland, to be parasitized by the third larval stage of the nematode Thynnascaria adunca. The nematodes were found in both the thorax and the abdomen, usually coiled. In some instances, the total length of the Thynnascaria adunca larvae was almost the same length as the Neomysis integer hosting it. Astthorsson (1980) suspected that the larvae would probably have an influence on the internal physiology of the host, but there is insufficient information concerning any effect upon the population that such parasitization may have.

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 Neomysis integer 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

Neomysis integer is not a species targeted for extraction. However, other mysid species have been harvested for human consumption and in Japan there is a commercial fishery of several species e.g. Neomysis intermedia, Neomysis japonica, Acanthomysis mitsukurii (Astthorsson, 1980).

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 Neomysis integer was found.