TA8 Field-Based Effects Measures
A105 & A106
8:00 AM - 12:00 PM, Tuesday

() Linking in situ bioassay responses with ecological effects in aquatic food webs.

Baird, Donald1, Maltby, Lorraine2, 1 National Water Research Institute (Environment Canada), Fredericton, NB, Canada2 Department of Animal & Plant Sciences, University of Sheffield, Sheffield, UK

ABSTRACT- The use of in situ bioassays in the assessment of effluent impacts on river communities involves more than just the deployment of laboratory test methods within the receiving environment. The use of relevant local organisms, drawn from a range of invertebrate functional categories (e.g. shredders, grazers) can offer the potential for increased understanding of the ecological effects of complex effluents with a minimal environmental footprint. The use of combined endpoints of mortality and feeding rate can permit the data obtained to be incorporated in ecological models (e.g. dynamic mass-budget physiological simulation models, matrix population models) permitting scenarios of altered stressor interactions to be assessed, and can deliver improved ecological focus for the regulatory assessment of anthropogenic discharges. Moreover, this coupling of data and models can be used to predict both the direct and indirect ecological consequences of stress along the ecological pathways of aquatic food webs. Using examples drawn from our own research, together with other studies carried out in Europe and North America, we address the issue of the ecological relevance of these techniques: can the data generated from bioassay organisms placed in river reaches used as a proxy for the ecological status of the surrounding river ecosystem? From the regulatory standpoint, we also address two key questions: What is the potential for these new methdologies to be incorporated into traditional aquatic ecosystem assessment techniques, and can their use improve our ability to diagnose causal agents in complex stress situations?

Key words: ecological relevance, in situ bioassay, food webs

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