Effects of chronic ammonium and nitrite contamination on the macroinvertebrate community in running water microcosms

In the present study, during a three-month exposure lethal and sublethal ef fects of ammonium and its products on typical brook organisms (Gammarus pul ex, Amphipoda; Radix ovata, Gastropoda; Limnephilus lunatus, Trichoptera) w ere monitored in microcosms approximating field conditions. Every 24 h duri ng this period the microcosms were contaminated with ammonium at five diffe rent nominal concentrations, which by chemical reactions produced a mixture of the toxic products ammonia and nitrite. G. pulex proved the most sensit ive to the ammonia and nitrite contamination resulting from the ammonium lo ad. In contrast, L. lunatus and R. ovata exhibited clearly effects only at concentrations 10 times higher. It is appropriate to investigate ammonium p ollution with its reaction products as a mixture, because in natural bodies of water receiving ammonium input (e.g., from sewage-treatment plants) the substances ammonium/ammonia and nitrite are likewise present simultaneousl y. (C) 2001 Elsevier Science Ltd. All rights reserved.