This project will develop, standardise and validate
a number of relatively simple laboratory multi-species toxicity tests for freshwater. Tests will be developed for pelagic and benthic organisms representing different trophic levels. The predictive value of these tests will be determined in field
experiments with lentic and lotic mesocosms.
To date the hazard assessment of chemicals has been
largely based on concentration-effect determinations in acute tests with a few test species. To enlarge the very restricted number of validated chronic toxicity tests a joint research
project (EEC contract EV4V-0110-UK (Development and validation of single species methods for evaluating chronic ecotoxicity to freshwater ecosystems)) is underway in 5 laboratories of
different EEC countries. However, single species toxicity tests do not give information on effects on species inter-relationships which determine functional and structural processes in ecosystems The effects of chemicals on these inter-relationships can be investigated using aquatic multi-species toxicity tests. There is therefore a need to develop ecologically relevant and reproducible laboratory multi-species tests; which are sufficiently simple and cost-effective for regular use by specialised laboratories.
Whereas acute toxicity tests with single species focus
mainly on mortality and single species chronic toxicity tests on mortality, growth and reproduction, the multi-species tests to be developed will use effects on species interactions as
endpoints e.g. effects on predation and competition.
Ecologically important species pairs, representing different trophic levels of the pelagic and benthic compartments, will be examined for their potential as test systems. Pelagic
systems will utilise micro-algae as primary producers and
rotifers and crustaceans as primary and secondary consumers. Benthic tests will examine epi and infaunal macro-invertebrate interactions using sediment based systems where appropriate. The initial phase of the laboratory programme will be the
selection of test species and establishment of appropriate
conditions for culture maintenance and testing. This will be followed by testing of reference chemicals with a wide variety of toxic effects and for which an extensive body of data from acute and chronic single species toxicity tests are available. Those chemicals being used in the ongoingstudy of single species chronic toxicity tests may prove acceptable.
Validation of the threshold toxicity values obtained in the
laboratory will require the use of field mesocosms with pelagic and benthic components in which the species interactions
utilised in the laboratory tests are of significance (e.g.
artificial streams, ponds and "aquatic lysimeters").
Effects monitored in the field mesocosms will not be limited to those interactions assessed in the laboratory tests but will be extended to cover a wide variety of sensitive and ecologically Significant parameters at the population, community and ecosystem levels. In the benthic test systems particular attention will be paid to the role of sediment in mediating toxic effects - an area of particular importance when working with chemicals of low water solubility or a high adsorbtion coefficient.
Funding SchemeCSC - Cost-sharing contracts
CF1 3TL Cardiff