The effects of pollution on benthic communities of the tidal James River, Virginia

Benthic communities in the estuarine portion of the James River are controlled mainly by salinity. Pollution effects are localized and difficult to assess because of the rigorous physical environment. Mesohaline and oligohaline communities were very similar to those in other east coast estuaries. except for the dominance of Rangia cuneata in the oligohaline zone. Communities of the tidal freshwater zone are most affected by pollution. In the areas of Richmond and Hopewell, where the major portion of the pollution load enters the river, communities are most severely depressed. Separate multivariate analyses of species distributional patterns, and pollution and physical parameters produced similar results dividing the river into mesohaline, oligohaline, and upper and lower tidal freshwater zones. Further analysis of only the tidal freshwater portion, to eliminate the effect of salinity, indicated that the distribution of benthic communities reflected the location and concentration of pollution sources along the river. The communities were dominated·by the introduced Asiatic clam, Corbicula manilensis, tubificids of the genus Limnodrilus and the chironomid larva Coelotanypus scapularis. The fauna of the freshwater zones was very eurytopic and adapted to the silty habitats that characterize the tidal freshwater James River and had great resemblance to the fauna of eutrophic lakes. The classical concept that a sharp increase in the number species occurs from the oligohaline to freshwater zones was found to be misleading. The increase does not occur until nontidal freshwater areas of greater habitat diversity are reached. Various aspects of the ecology of the poorly known tidal freshwater habitat are also discussed. This dissertation is from the Joint Program Degree from the College of William & Mary and University of Virginia and awarded by the University of Virginia