MORTALITY AND A DRIFT-RELATED RESPONSE OF THE FRESH-WATER AMPHIPOD GAMMARUS-PULEX (L) EXPOSED TO NATURAL SEDIMENTS, ACIDIFICATION AND COPPER

The mortality and a drift-related response of juvenile Gammarus Pulex (L.) exposed for 10 days to natural sediments and to copper treatments in the presence of a sediment were recorded. Tests were performed under non-acidified and acidified conditions. Mortality of G. pulex exposed under non-acidified conditions was not greater than 20%. Acidification caused an increase in mortality related to the buffering capacity of the sediments and the test concentrations of copper. Sediment type affected the drift response under non-acidified and acidified conditions. Gammarids in systems ultimately causing the highest mortality spent the most time in the water column for each 'sub-lethal' exposure period. The behavior of G. pulex was affected by the copper treatments in a dose-related manner, and responses in the 702, 942 and 1343 mug l-1 initial test copper concentrations were significantly higher than in the control. Acidification accentuated behavioral differences and gammarids in the 136 mug l-1 initial copper test concentration had a significantly higher drift response than control animals after 168 h of exposure. The findings are discussed with respect to the buffering capacities of test systems, the fate of copper under non-acidified and acidified conditions, and the potential of drift for assessing the hazard of chemicals.