ABSTRACT
In breeding experiments with euryoecious macrozoobenthos species, it was demonstrated that both embryonic and juvenile development were less impaired by hypoxic conditions than by chemical factors that may occur in a benthic environment under such conditions. These factors include increased nitrite concentrations in nitrate loaded sediments, or sulphide in the anoxic zone of eutrophic lakes. Laboratory experiments demonstrated that for the species Chironomus piger, Theodoxus fluviatilis, Bithynia tentaculata, Radix peregra, Limnodrilus hoffmeisteri, and Tubifex tubifex development is still possible even in low oxygen concentrations. However, the development of Chironomus larvae became impaired by nitrite concentrations above 1 mg/L, and Limnodrilus hoffmeisteri similarly by sulphide concentrations of about 1 mg/L. When studying the effects of pesticides on freshwater indicator species, the ecophysiological consequences of nitrate, nitrite and sulphide concentrations also have to be investigated carefully, as well as other abiotic conditions such as oxygen, temperature and pH.
