Blackwell Publishing Journal Backfiles 1879-2005
SUMMARY. The freshwater littoral meiofauna along a temperature gradient in Par Pond (a cooling reservoir receiving thermal effluents from a nuclear reactor) was sampled from September 1975 to October 1976. Monthly samples were taken at three stations; ‘hot-water’ (15–40°C), ‘warm-water’ (13–37°C) and ambient or ‘cold-water’ (8–37°C) sites. Total numbers of individuals at the ambient site ranged from 971 to 3674 per 10 cm2 (mean = 2263), approximating the density reported from productive estuarine environments. Nematodes, rotifers, ostracods, cladocerans and mites comprised 80% of overall density. When compared to the ambient site, thermally affected sites demonstrated reduced faunal density.Contrary to other environmental perturbation studies, the Shannon-Weaver diversity index (H') did not reflect alteration of structural complexity within the rotifer taxocene when hot-water, warm-water and cold-water sites were compared. Though there was a significant reduction in number of species at the thermally altered sites, high ‘equitability’ among the reduced species resulted in H’ values comparable to those in natural communities. Distinct winter-spring and summer-autumn assemblages were evident in the ambient community while no seasonal clustering was apparent at the thermally affected sites. It is hypothesized that the maintenance of temperatures above ambient normals masks environmental cues that normally would elicit seasonal changes in the rotifer fauna at those two sites.
Type of Medium: