Impact of the fungicide carbendazim in freshwater microcosms. I. Water quality, breakdown of particulate organic matter and responses of macroinvertebrates

Effects of chronic application of the fungicide Derosal(R) (active ingredie nt carbendazim) were studied in indoor macrophyte-dominated freshwater micr ocosms. The concentrations (0, 3.3, 33, 100, 330 and 1000 mu g/l) were kept at a constant level for 4 weeks. This paper is the first of a series of tw o, and describes the fate of carbendazim and its effects on water quality p arameters, breakdown of POM, and responses of macroinvertebrates. Carbendaz im proved very persistent in the water layer. Values for t(t/2) varied betw een 6 and 25 weeks, and decreased with the treatment level. Significant eff ects on water quality parameters (DO, pH, alkalinity, conductivity) could n ot be demonstrated. After 4 weeks of incubation, the breakdown of Populus l eaves was significantly slower at the two highest carbendazim concentration s. The macroinvertebrate community was seriously affected by carbendazim ap plication, with Oligochaeta, Turbellaria, Hirudinea and some Crustacea as t he most sensitive groups. The snail Bithynia decreased in numbers, but othe r gastropods increased in numbers. Safety factors as proposed by the Unifor m Principles (European Union) for the risk assessment of pesticides, to be multiplied with toxicity data of the standard test species (Daphnia, fish, algae), appeared to ensure adequate protection of sensitive populations pre sent in the microcosms. (C) 2000 Elsevier Science B.V. All rights reserved.