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2001
Conference Paper
Titel
Effects of the use of plant protection products on aquatic species - a monitoring approach
Abstract
In order to obtain a more realistic picture of the real effects of agricultural practice and crop protection use on macroinvertebrate communities of neighbouring aquatic systems, a retrospective approach similar to the RIVPACSystem was chosen: In two agricultural regions in Germany differing in crops and cultures, ditches and small brooks were sampled for the benthic macroinvertebrate communities. Samples were collected at 40 sites of each region, differing in the predictable loads from the use of crop protection products in the drainage area. Based on these data, the sites were clustered by using the TWINSPAN approach. By multiple discriminance analyses (MDA) of the site clusters including habitat and exposure parameters, the main factors influencing species composition in autumn 1998, in spring, summer and autumn 1999, and in spring 2000 have been and will be identified. The results of the applied statistical approach are compared with results of a principle component analysis (PCA) followed by the principle response curve approach (PRC). First results from the region "Altes Land" near Hamburg, which is characterized by extremely high exposure of surface waters and a very definite exposure situation, were obtained from the autumn 1998 and spring 1999 samplings. No significant effect of land use patterns or exposure on species richness could be observed. With respect to species composition, significant effects could be observed in autumn 1998 and spring 1999. They were less significant than those by a few other influence factors (e.g. water depth), and decreased from autumn to spring. The results of the two statistical approaches have to be compared with respect to the single influencing factors. The taxa being sensitive towards the different influences will be identified. The inclusion of the summer data will clarify the extent of the acute effects, the inclusion of the next autumn and spring data will enable the quantification of the recovery. The data set of the second region will be evaluated in the same way to enable comparisons and clarify possibilities of extrapolation.