Long-term in situ toxicity bioassays of the Reconquista River (Argentina) water with Cyprinus carpio as sentinel organism

The toxicity of the Reconquista River water at Cascallares, a relatively low polluted point, was determined by means of bioassays with juvenile Cyprinus carpio as a test organism. During the summer of 1995-1996, three 30 days-long in situ caged fish tests were conducted. Changes in the activities of branchial (Na+, K+)- and Mg++-ATPases and brain AchE of fish were studied. The chemical profile of the river water showed that heavy metals and phenols were the main pollutants. Gill ATPases activities were altered, while brain AchE activity resulted inhibited in one of the assays. (Na+, K+)-dependent activity was inhibited approximately 20% as compared with controls; in two assays Mg++-ATPase activity was stimulated. The condition factor of caged fish did not differ from controls. Since the protein content of gills was slightly altered, the detected changes in the enzyme activity should not be linked to alterations in the protein synthesis.