The environmental risks of pollution in the Scheldt estuary
In: Netherlands Journal of Aquatic Ecology. Kluwer Academic Publishers/Netherlands Society of Aquatic Ecology: Bilthoven. ISSN 1380-8427; e-ISSN 2214-7098, meer
Ook verschenen in:Meire, P.; Vincx, M. (Ed.) (1993). Marine and estuarine gradients: ECSA 21: Proceedings of the 21st symposium of the Estuarine and Coastal Sciences Association held in Gent, 9-14 september 1991. Netherlands Journal of Aquatic Ecology, 27(2-4). Netherlands Society of Aquatic Ecology: Bilthoven. 496 pp., meer
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| Abstract |
The ecotoxicological effects of pollution in the Scheldt estuary is evaluated for several routes of exposure by comparing observed concentrations of micro-contaminants in water and tissues of biota with toxicity data in literature. Ecological risks are estimated for dissolved trace metals according to the method of VAN STRAALEN (1990) using published data on NOECs from aquatic toxicity tests concerning reproduction, mortality and growth for cold blooded marine and estuarine organisms. Of eight investigated trace metals, zinc and nickel cause the highest risks, both affecting up to 4% of the aquatic species. The occurrence of bioaccumulation of PCBs and cadmium is investigated in several trophic levels. High concentrations of PCBs are observed in tissues of biota and may indicate adverse effects on top predators (seals, terns), especially in the brackish zone. Environmental risks of other organic micro-contaminants have not been indicated due to the limited number of data on toxicity or environmental concentrations. The effects of a mixture of pollutants in sediments from the Scheldt estuary were investigated with an oyster larvae bioassay showing an increased toxicity in upstream direction. Moreover, in the upper part of the estuary, preconditions regarding the oxygen concentration are not met and overshadow the toxic effects of pollution with micro-contaminants. Especially in the less contaminated part of the estuary more ecotoxicolgical research is required to perform an integral risk evaluation. At present, still little is known about effects that may occur in the field. |
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