Abstract
Grazing potential (GP, in % day−1) was estimated for the plankton communities of 13 Greek lakes covering the trophic spectrum, in order to examine its sensitiveness in discriminating different classes of ecological water quality. Lakes with high GP values exhibited high zooplankton biomass dominated by large cladocerans or/and calanoids while lakes with low GP values had increased phytoplankton biomass and/or domination of small-bodied zooplankton indicating intensive fish predation. GP successfully distinguished among ecological water quality classes (estimated using the phytoplankton water quality index PhyCoI) indicating its potential use as a metric for ecological water quality assessment. As a next step, PhyCoI index was modified to include GP as a metric in order to enhance the phytoplankton-based ecological status classification of lakes incorporating zooplankton as a supporting factor. The PhyCoIGP successfully assessed the ecological water quality in accordance with PhyCoI classification whereas it was significantly correlated with the eutrophication proxy TSISD based on Secchi Depth. Thus, we propose to use the modified phytoplankton index PhyCoIGP for monitoring the ecological water quality of lakes.
Highlights
Over the last two decades, different legislation acts such as the Water Framework Directive (WFD)and the Marine Strategy Framework Directive (MSFD) in Europe, the Water Act in Australia, the USClean Water Act (CWA) and the South African National Water Act, all having as a main goal to maintain and enhance the ecological integrity of freshwater and marine ecosystems, focus on the assessment of the ecological water quality of water bodies [1]
We have shown that the grazing potential (GP) index applied to zooplankton and phytoplankton communities of lakes can identify different classes of ecological water quality based on the functional traits of both plankton communities weighting copepods as partially inefficient grazers and some phytoplankton groups of poorly edible algae
Lakes with high GP values have high zooplankton biomass dominated by large cladocerans or/and calanoids while lakes with low GP
Summary
Over the last two decades, different legislation acts such as the Water Framework Directive (WFD)and the Marine Strategy Framework Directive (MSFD) in Europe, the Water Act in Australia, the USClean Water Act (CWA) and the South African National Water Act, all having as a main goal to maintain and enhance the ecological integrity of freshwater and marine ecosystems, focus on the assessment of the ecological water quality of water bodies [1]. The Marine Strategy Framework Directive (MSFD) in Europe, the Water Act in Australia, the US. 2000/60/EC [2] introduced the ecological status classification of water bodies based on biological quality elements (BQEs), i.e., phytoplankton, benthic macroinvertebrates, fish, aquatic macrophytes and phytobenthos. The EU Member States and other participating countries have developed and adopted legislation for the assessment of the ecological integrity of surface waters with the intercalibration of 230 evaluation systems and the development of numerous indices/metrics for each BQE (e.g., benthic macroinvertebrates: Lake Acidification Macroinvertebrate Metric (LAMM), ETO (Ephemeroptera, Trichoptera and Odonata) taxa richness and Chironomid pupal exuvial technique (CPET) index; fish: Abundance index of alien species, mean catch per unit effort in terms of number (NPUE) of the guiding. The Common Implementation Strategy (CIS) acknowledging the need of monitoring the top-down control indicates zooplankton as a ‘supportive/interpretative parameter’
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