THE SPECIFICITY OF MEIOBENTHIC COMMUNITY RESPONSES TO DIFFERENT POLLUTANTS - RESULTS FROM MICROCOSM EXPERIMENTS

In preliminary microcosm experiments we have been able to demonstrate a clear differential response of meiobenthic assemblages to zinc, copp er and cadmium contamination. Sediment and natural meiobenthic communi ties were collected from two estuaries, the Lynher (mud with a high or ganic content) and Exe (sand with a low organic content). The sediment s were dosed separately with zinc, copper and cadmium at three differe nt dose levels. The meiobenthic community structure from both sites wa s unaffected by cadmium at any of the dose levels. The communities in the zinc and copper treatments were significantly different (ANOSIM p < 0.05) from each other and from the controls (and cadmium treatments) . Although the differential response occurred in both sediment types, its intensity was greater in the sand than the mud. The Exe sand commu nities were much more strongly affected by the contaminants, even at t he lowest dose, copper having a more severe effect than zinc. The Lynh er mud meiobenthos was most strongly affected by the zinc treatment an d there was a graded response to both zinc and copper with significant differences in the communities at different doses (ANOSIM p < 0.05). These differences between sediments could be due to the binding of met als onto organic material, thus reducing their availability to the fau na.