Inhaltszusammenfassung

Information about the effects of agriculturally derived insecticide input on the aquatic fauna in the field is sparse. Runoff- related insecticide input and the resulting toxicological effects on the aquatic fauna (abundance, drift, emergence) at three sampling sites at different distances (450-1150 m) from the input location of contaminated edge-of-field runoff (erosion rill) were investigated. By means of event-triggered sampling it was shown that the transient (about 1 h) insecticide conta...Information about the effects of agriculturally derived insecticide input on the aquatic fauna in the field is sparse. Runoff- related insecticide input and the resulting toxicological effects on the aquatic fauna (abundance, drift, emergence) at three sampling sites at different distances (450-1150 m) from the input location of contaminated edge-of-field runoff (erosion rill) were investigated. By means of event-triggered sampling it was shown that the transient (about 1 h) insecticide contamination in the stream was very high (e.g. 6 mug l-1 parathion-ethyl in water, 302 mug kg-1 fenvalerate in suspended particulates). The rates of loss of applied substance calculated on the basis of the application rate, the concentrations measured in the stream, and discharge data for both insecticides were below 0.1reported in the literature. The measured insecticide contamination in the stream had a strong negative effect on the aquatic macroinvertebrate community. Eight of the 11 common species vanished from 19 May on for a period of 3-6 months, although their life cycles include much longer aquatic stages. The remaining three species were significantly (P < 0.001) reduced in their population density, although in their normal life cycle the population density would increase due to summer reproduction. These effects were observed for the entire longitudinal stream section investigated (up to 1150 m from the edge-of-field runoff location). In contrast, the increase of drift rate (mainly G. pulex) and of the mortality in the drift (mainly caddisfly species), declined with increasing distance from the runoff site. The comparison of runoff events with and without insecticide contamination substantiates the crucial importance of the insecticide contamination for the observed effects. There was no correlation between the hydraulic component (discharge), turbidity or nutrient content and the observed toxicological effects (decrease in number of species, increased drift; increased mortality in the drift) on the aquatic fauna. Considering all these facts, it can be concluded that agricultural insecticide input may play an important role in the dynamics of macroinvertebrate communities in agricultural streams.» weiterlesen» einklappen

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