North Sea benthos: A review of field investigations into the biological effects of man's activities

This paper reviews English-language publications on the benthic fauna of the North Sea, with particular reference to those studies aimed at assessing the effects of man's activities. Coverage includes estuaries and coastal waters of the eastern United Kingdom, Belgium, The Netherlands, the Federal Republic of Germany, and the western coastlines of Denmark, Sweden, and Norway, as well as offshore areas. There are regional differences in the amount of evidence available for linking changes in the coastal benthos with anthropogenic influences, reflecting not only differences in the nature and magnitude of activities, but also variations in coastal topography and prevailing hydrographic conditions which may or may not ameliorate the effects. Where such effects have been clearly demonstrated, these have invariably been confined to areas of limited water exchange, or in the vicinity of discharge points. Offshore, the weight of evidence favours the view that no significant benthic changes appear to occur as a result of waste discharge, excepting close to known sources of input, e.g, oil production platforms. However, these changes are very localized and are of little significance relative to the sea area as a whole. Recently, attention has been focused on the possible consequences for the marine ecosystem of an increasing trend of nutrient inputs to certain coastal areas from anthropogenic sources. Regarding the benthos, some comparisons with historical data have been possible, though as yet there is no unequivocal evidence to link changes - where observed - with eutrophication. A persistent concern in benthic studies is the ability to account for, and hence distinguish between, natural effects and those which may be attributable to low-level contamination. This is especially true in inshore environments where marked seasonal or year-to-year changes in abundance and biomass of short-lived species are commonly recorded. In the longer term, benthic communities may also respond to cyclical changes in climate on a variety of time scales. These factors emphasize the general value of extended time-series data in the evaluation of ecosystem changes, and also the importance of “control” sites in monitoring trends in the biota in relation to contaminant inputs.