Introducing a zooplanktonic index for assessing water quality of natural lakes in the Mediterranean region

In the pelagic food web of lakes, zooplankton offers the linkage between phytoplankton and fish, greatly affecting but also mirroring the functionality and stability of the ecosystem. Despite the increased interest on the development of water quality indices, incorporating zooplankton data on metrics used for the assessment of natural lakes remains a challenge. Here, we used information of natural lakes hosted in Eastern Mediterranean on zooplankton abundance, biomass, body weight and cladocerans' ratio to develop a novel zooplanktonic index (Zoo-IQ). Α 5-grade classification scheme was generated (Bad ≤6, 6 < Poor ≤10, 10 < Moderate ≤14, 14 < Good ≤18, 18 < High) for water quality assessment. The Zoo-IQ was originally parametrized based on data collected from 13 natural lakes, located in Greece and successfully classified hypertrophic lakes with poor quality and deep lakes with good quality, while it identified lakes subjected to restoration actions. Using independent data from five lakes hosted in Greece, Turkey and Croatia, Zoo-IQ successfully assessed their water quality. Specifically, from the 25 sampling cases, used for the development and the evaluation of the index, Zoo-IQ identified 5 as good, 8 as moderate, 11 as poor and 1 as bad. Our results demonstrate the potential of using Zoo-IQ for the assessment of lakes water quality in the Mediterranean. The proposed index could serve as a first step towards the development of similar indices in other climatic zones.