Abstract
The European Water Framework Directive implements the policies to achieve a good ecological status of all European waterbodies. To determine the ecological potential in freshwater environments, abiotic (morphology, physical and chemical variables) and biotics (algae, fishes, etc.) metrics are used. Despite their importance in trophic web, zooplankton was not included as one of the Biological Quality Elements (BQE) to determine the water quality. In the present research, we studied the zooplankton species that can be considered as indicators of trophic status and ecological potential for more than 60 water reservoirs. The data were obtained from more of 300 samples collected during 10 years from reservoirs at Ebro River watershed, which is the largest basin in Spain. According to their physicochemical and biological elements, the trophic status and ecological potential of these reservoirs were established. More than 150 zooplankton species were identified during the study. The results from this research indicate that species that are related with low water quality are: Acanthocyclops americanus, Ceriodaphnia spp., Daphnia cucullata, Daphnia párvula, Diaphanosoma brachyurum, Brachionus angularis, Keratella cochlearis and Phompolyx sulcata. An indicator of moderate quality was Bosmina longirostris, while Daphnia longispina, Ascomorpha ovalis and Ascomorpha saltans were considered as indicators of good water quality. The data obtained suggest that zooplankton species can be used as a valuable tool to determine the water quality status and should be considered, in a near future, as one more of the BQE within the WFD metrics.
Highlights
There is an ever-increasing pressure on water resources and freshwater cultural eutrophication (Schindler 2012)
The aim of this study was to determine the species of the three main zooplankton groups that are good indicators or are related to different trophic states in the reservoirs located in the Ebro watershed, using a robust data set collected during the last ten years in 66 reservoirs involving more than 300 sampling occasions
An integrative water sample was collected from the photic zone of each reservoir using a 25-mm-inner-diameter ballasted PET tube, and when photic zone was lower than 6 m deep, an integrative water sample was collected from the water surface until this depth or to the bottom (Vicente et al 2005)
Summary
There is an ever-increasing pressure on water resources and freshwater cultural eutrophication (Schindler 2012) This cultural eutrophication is due to the increase in nutrient input (mainly nitrogen and phosphorus) directly into lakes, reservoirs, rivers or inside the catchment basin area. The BQE algae is one of the most used and accepted indicators to evaluate the ecological potential using plankton data. Zooplankton, despite their fundamental position in food webs (Haberman and Haldna 2014) in freshwater ecosystems, was surprisingly not included (Moss 2007) and without a scientifically sound explanation for their omission (Caroni and Irvine 2010; Jeppesen et al 2011; Moustaka-Gouni et al 2014)
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