hrvatski

Indirect influence of pesticides on macroinvertebrate community of constructed lakes

Synthetic pesticides are substances used to control pests of both animal and plant origins on agricultural land. These substances often find their way to aquatic ecosystems by runoff where their effect on non-targeted aquatic invertebrates, plants and fish can range from individual to community level. In constructed lakes created by damming, the risk of accumulating these harmful substances is potentially greater than in other surface waters. Pesticide runoffs occur directly in the drainage basin of the artificial water bodies and along the longitudinal drainage surface of the tributary running water(s). Our main hypothesis was that persistent exposure even to “acceptable pesticide levels” alter the aquatic macroinvertebrate community equilibrium, decreasing the abundance of specific predator groups with longer generation time (namely dragonflies and water mites), favoring thus r-type selected species. Preliminary screening samples of macroinvertebrate communities were taken in autumn of 2016 from 10 constructed lakes located in the agricultural-land-dominated Pannonian Lowland Ecoregion of Croatia. Ten subsamples at each site were collected using benthos hand net (500 μm). Monthly measurements on eight pesticide types were collected from 2010-2016 in tributary rivers close to the mouth of the constructed lakes. Significant correlations were determined between the share of agricultural land cover present in the drainage area and pesticide concentrations. A multiple linear regression model showed that r-dominance (ecological quality bioassessment metric) increased with increasing pesticide concentrations. Increased concentration of pesticides was also found to be detrimental to predator groups with longer generation time and a smaller number of offspring (K-selected species).

pesticides, macroinvertebrate community, reservoirs

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