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(33-05) Cadmium effects on species interactions: responses of an experimental aquatic food web. Riddell, David*,1, Baird, Donald1, Culp, Joseph2, 1 University of Stirling, Stirling, UK2 National Water Research Institute, Saskatoon, Canada ABSTRACT- This study seeks to develop an approach to effects testing employing behavioural endpoints which can be used to resolve subtle, yet potentially important responses to environmental contamination. The foraging and predator-avoidance behaviours of mayfly (Baetis tricaudatus) nymphs and predator-prey interactions were investigated under differing combinations of toxicant concentration and predation risk. Predators consisted of stonefly (Kogotus nonus) nymphs, juvenile brook trout (Salvelinus fontinalis) and longnose dace (Rhinichthys cataractae), either alone or in combination. Organisms were exposed to 0, 0.5 and 5.0 Key words: food web, aquatic, behaviour, metal |
g l-1 cadmium for 7 days (invertebrates) or 30 days (vertebrates) prior to observation in artificial stream channels. Behavioural observations were of 20-min duration. Mayfly feeding rate was assessed by image analysis of grazed diatom mats cultured on ceramic tiles. Cadmium exposure significantly reduced the proportion of time stoneflies were active and reduced mayfly grazing at the higher concentration, but otherwise had little effect on invertebrate behaviour. Contrastingly, the presence of predators significantly affected invertebrate behaviour. Mayfly drift rate increased in the presence of stoneflies and decreased in the presence of trout. Trout and dace also significantly decreased both number of mayflies present on tile surfaces and time spent active by stoneflies. Compared to controls, 5.0