The effect of persistent pollutants on aquatic ecosystem: A complex study

Wastewaters entering receiving water bodies become one of the main factors of pollution of natural waters; since they change the water and bottom sediment chemical composition, destroy the biological balance of the self-cleaning processes and finally can cause unpredictable changes in the ecosystem. Wastewater persistent pollutants (heavy metals) are the most dangerous as they migrate and accumulate in organisms in ecosystems. Heavily, and permanently polluted aquatic ecosystems are still found in Lithuania, which is the target of a complex ecotoxicological (experimental-field and hydrochemical) investigation. Water pollution assessment by use only physico-chemical methods do not provide integrated information on the effects of pollutants on aquatic life because toxicity is a biological characteristic. Investigations should be carried out under controlled laboratory conditions on test-objects of different trophic level, phylogenesis and ontogenesis (higher plants, leeches, daphnids, and fish), taking into account the test-set of functions. The peculiarities of test-objects and their test-functions to the effect of wastewater, natural water and bottom sediment persistent pollutants as well as their distribution in natural waters and bottom sediments should be investigated. The sensitivity and specificity analysis of the test-objects and their test-functions should be performed revealing functional alteration mechanisms and organism adaptation capabilities, which ensure the survival of individuals and populations. Complex experimental-field and hydrochemical studies will enable to extrapolate obtained experimental results to natural environment and predict possible consequences of the pollutant effect on organism-population-community set. Bioindication studies of ichthyofauna populations and communities should be performed as well as permanent pollutant (heavy metals, priority) bioaccumulation in fish as the highest of organisms of the trophic chain should be established. The use of European and Lithuanian fish index (LFI) will enable to assess the ecological status of the water body studied. Complex evaluation of biotesting, bioindication and hydrochemical study results of the permanently polluted water ecosystem could allow the extrapolation of experimental data into natural environments and to predict persistent pollutant potential impact of on the individuals, their populations and communities.