acute toxicity, Eisenia foetida, acetylcholiesterase, Odra river basin, organophosphate pesticides

The aim of this study was to investigate the influence of anthropogenic activities on the level of toxicity of river sediments near agricultural areas under cultivation. The evaluation of the acute toxicity of samples was carried out by contact test on earthworms of the genus Eisenia foetida. Neurotoxic potentiality of organophosphate pesticides present in the samples was assessed by measuring the inhibition of the enzyme acetylcholinesterase (AChE). Sampling was from 9 watercourses in the north Moravian and the north Bohemian part of the Odra river basin. Sediments were evaluated for toxic effects on the earthworms (Eisenia foetida). The average mortality of test organisms ranged between 0 - 14.25%. The inhibition of the enzyme acetylcholinesterase activity was detected in all samples of bottom sediments from rivers. For comparison, soil samples from the bank part of the rivers and soil samples from fields that are in close proximity to watercourses were also evaluated. Results of the study indicate contamination by substances that inhibit the enzyme acetylcholinesterase activity in the monitored river sediments, and also in some soil samples from the riverbanks. Monitoring of mortality in a standard acute toxicity test appeared to be a less sensitive parameter of the evaluation, in comparison with the determination of the inhibition of the enzyme acetylcholinesterase.