Limnetica 40
The neglected zooplankton communities as indicators of ecological water quality of Mediterranean lakes
The exclusion of zooplankton as a biological quality element from the Water Framework Directive, led to the decreased monitoring of zooplankton communities all over Europe, including Greece. Patterns of abundance, biomass and size structure were investigated in 13 natural Greek lakes covering the whole trophic spectrum and representing various aspects of ecological water quality (high, good, moderate, poor), to identify metrics representing zooplankton community structure and size for ecological water quality assessment in the Mediterranean area. In the studied lakes, rotifers had generally the highest contribution in zooplankton abundance, while copepods had the highest contribution in zooplankton biomass. Small-bodied zooplankton probably dominated due to intense fish predation and prolonged cyanobacterial blooms. Based on the variation of abundance, biomass and the size structure five zooplankton metrics, i.e. total abundance (AZoo), total dry biomass (BZoo), zooplankton ratio (RZoo), mean zooplankton weight (MWZoo) and cladocerans ratio (RClad), were tested against phytoplankton biomass as the eutrophication state variable and PhyCoI as the phytoplankton ecological water quality index. All five zooplankton metrics were significantly correlated with phytoplankton biomass and/or identified different trophic state classes and were also correlated with ecological water quality. The five studied zooplankton metrics were found to be promising indicators for ecological water quality assessment and as such we propose them to be included in the monitoring programs of natural Mediterranean lakes.
