Long-term Effects of Bioaccumulation in Ecosystems

Abstract

Extensive damage to organisms and declines in wildlife populations have been observed together with long-term bioaccumulation and biomagnification of persistent xenobiotic chemicals. Heavy metals, especially organic or biomethylated mercury, lead, cadmium and organic tin compounds have caused environmental damage through bioaccumulation on a local scale. Effects on wildife caused by bioaccumulation of persistent organochlorine compounds are more widespread. However, the causal relationship between a biomagnified compound and the long-term effects have been established in only a few cases. Metabolic transformations, and occurrence of several toxic contaminants together in many cases, complicate evaluations of the sources of long-term effects. Environmental fate, exposure of biota and biomagnification of a chemical can be predicted by modelling from its properties and from ecological, geological and climatic conditions of the recipient environment. Model predictions can be refined by experimental factors obtained from results of the field studies. Empirical estimates of hazardous bioaccumulation or biomagnification are obtained from field analyses of different trophic levels. Trend analyses of biomagnified contaminants and their effects can be utilized in prognosis of future development and in evaluation of the need for further action to protect the environment and human health. List of List of Symbols and Abbreviations IntroductionMan-made chemicals have caused deaths of wildlife populations due to serious dumpings, industrial discharges and accidental spills. In many cases the causal linkage between certain toxic chemical and damage has been obvious. In many other cases epidemic deaths of animal populations or vegetation has been suspected to be caused by an acute exposure to chemicals but not verified. Ecological damage from chronic exposure is even more difficult to explain. Long-term studies on the occurrence of anthropogenic chemicals in the environment, their effect potencies and their monitoring in connection with specific episodes have, however given some specific answers. These results justify the conclusion that some persistent anthropogenic chemicals are causing eco- Long-term Effects of Bioaccumulation in Ecosystems203 logical damage such as the decline of populations through breeding losses or developmental damage as a result of bioaccumulation and biomagnification in the environment. Observed Effects from Bioaccumulation MercuryMercury is mobilized in the environment mainly from sources related to human activities [1,2]. Its ecotoxic effects were first observed in Sweden during the period 1948-65, where excess mortality of seed-eating birds was found to be caused by methyl mercury used as seed dressing fungicide [3,4]. Serious human mass poisonings from seafood in the early 1950s in Minamata and the early 1960s in Niigata were due to alkylmercury discharged from chemical manufacturing plants being bioaccumulated in fish and crustacea consumed by people [5]. Symptoms, e.g. visual field impairment, ...

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