Impairment of mysid (Neomysis integer) swimming ability: an environmentally realistic assessment of the impact of cadmium exposure.
Neomysis integer (Crustacea: Mysidacea), a euryhaline member of the hyperbenthos of the upper reaches of European estuaries, has been identified as a suitable animal for assessing the impacts of chemical pollutants on these estuarine regions. In this study, the effect of a 7 day pre-exposure to environmentally relevant concentrations of cadmium (0.5 and 1.0 microg l(-1)) on the swimming behaviour of N. integer was examined using an annular flume. Cadmium speciation at two salinities (1 and 10 per thousand) that dominate these upper estuarine regions was modelled to ensure mysids were exposed to the same concentration of the toxic free-ion at each salinity. There was no significant difference in the swimming behaviour of mysids exposed to the same free-ion cadmium concentration at the two different salinities. At each salinity, exposure to 0.5 microg Cd2+ (aq) l(-1)resulted in fewer mysids moving forward into the current (normal behaviour) at free stream velocities typical of their natural habitat (e.g. 3-9 cm s(-1)) than non cadmium-exposed mysids. At these low current speeds, cadmium-exposed mysids were either able to maintain position or were swept by the current. The same general responses were recorded for mysids exposed to 1.0 microg Cd2+ (aq) l(-1)except that more mysids showed disrupted swimming ability compared with 0.5 microg Cd2+ (aq) l(-1). At higher current speeds (>12 cm s(-1)), current velocity was the dominant factor affecting mysid swimming behaviour and there was no effect of cadmium on mysids maintaining position. Exposure to cadmium also caused significant disruption of the hyperbenthic behaviour of N. integer and more cadmium-exposed individuals were in the water column than control mysids; this result was more variable at 10 per thousand than 1 per thousand. Results indicate that exposure to cadmium concentrations of 0.5 microg Cd2+(aq) l(-1)would result in displacement of N. integer from its optimum region within the estuarine environment. This conclusion would not be achieved from standard LC(50) tests (e.g. 7 day LC50 = 2.95 microg Cd2+ (aq) l(-1)), highlighting the value of behavioural disruption as a sensitive indicator of environmental chemical contamination.
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Plymouth Environmental Research Centre (Department of Biological Sciences), University of Plymouth, Drake Circus, PL4 8AA, Plymouth, Devon, UK.
Widdows
J
J
Jones
M B
MB
D000818:Animals; D002104:Cadmium / Q000493:pharmacokinetics; D002105:Cadmium Poisoning / Q000503:physiopathology / Q000662:veterinary*; D003445:Crustacea / Q000378:metabolism / Q000502:physiology; D013550:Swimming; D014877:Water Pollution, Chemical / Q000009:adverse effects
D002104:Cadmium