A cost-effective tool-box to assess ecological receptors at most risk in a potentially pesticide contaminated south European big man-made reservoi

Abstract

South European man-made reservoirs are essential sources of freshwater with multiple uses such as water supply, electricity, irrigation and recreation. However, pollution especially from agricultural activities is threatening the environmental quality of these water bodies. As modern agricultural practices require the usage of pesticides such herbicides, fungicides and insecticides to prevent losses by pests, possible negative impacts on ecosystems should be evaluated. In Europe, the Water Framework Directive (WFD) has assumed an active role at aiming to preserve and restore the biodiversity of inland water, wetlands, and coastal areas to achieve the “Good ecological status” of water bodies till 2015. This project aimed at (1) identifying the ecological receptors at most risk in the Alqueva reservoir – an impacted water reservoir previously shown to be contaminated with pesticides, and (2) putting forward a tool-box of short-term sub-lethal cost-effective tests to be used in future routine monitoring. Water and sediment samples from five and one sampling stations at the selected contaminated – Alqueva – and reference – Beliche – reservoirs, respectively, were collected during February 2012. Toxicity was evaluated with a battery of laboratory assays including representative species of different taxonomic and functional groups. Assay endpoints for water samples included: luminescence of the marine bacteria Vibrio fischeri, growth of the green microalgae Pseudokirchneriella subcapitata, survival of the fairy shrimp Thamnocephalus platyurus, reproduction and feeding of the planktonic cladoceran Daphnia magna, growth and feeding of the zooplanktivorous fish Danio rerio. Assay endpoints for sediment samples included: luminescence of V. fischeri, growth of the benthic ostracod Heterocypris incongruens, growth and feeding of the benthic midge Chironomus riparius. Overall, no toxicity evidence was found at the Alqueva reservoir. This fact was associated to a severe drought registered several months prior to sampling as well as changes in agricultural practices, which might have prevented the input of pesticides through runoff from agricultural fields. The weak anthropogenic pressures at Beliche together with the ecotoxicological evidence of the lack of detrimental effects supported the proposal of this reservoir as a reference site.