Response of benthic fauna to different pollutants: Some case studies and relevance of benthos to environmental impact assessment

Abstract

With rapid rate of urbanization, industrial growth and varieties of anthropogenic changes, the use of biological parameters as monitors of environment is being increasingly appreciated. As compared to plant, the animal communities have been used to a greater extent in toxicity tests and pollution monitoring programme. Biological monitoring thus precisely aims at locating adverse effects in terms of damage done to biota as a consequence to environmental deterioration caused by pollutants. Thus understanding of the mechanisms of ecological functions/parameters responsible for seasonal fluctuations in biological communities is an essential prerequisite in marine ecological monitoring programme. It has been stated that monitoring fluctuation is easy, but without an understanding of causal mechanism only the most obvious effects of pollution will be observed. Once accepted the importance of monitoring, it is necessary to decide about the suitable parameters to be monitored. If a large part of the variance of parameter is found in the high frequencies of space and / or time, that parameter in general is unfit for monitoring. Benthos is a distinct entity among the biological components of marine ecosystem, directly related with bottom sediment. The distinction of benthic organisms lies in the sedentary and sessile life. Benthic fauna is represented by almost all invertebrate phyla. Seasonality in shallow water benthic fauna is a common feature, whereas the subtidal benthos shows more uniformity and steady distribution unlike planktonic and nektonic forms. This is possible because of more or less stable subtidal benthic environment. Therefore, the qualitative and quantitative abundance in space and time will be suitable parameters to understand ecological functioning and monitoring of environments. Benthos has a good history as bonafide community of environmentally disturbed ecosystems. They are the first casuality of any environmental disturbances. Benthic community structure is therefore being widely used in pollution monitoring programmes but often with equivocal results. This paper summarizes results of some case studies of benthos under different stress conditions and suggests the distinctness of benthic data as tool in environmental impact assessment studies