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Due to its fundamental position in the aquatic food chain linking primary producers (phytoplankton) to higher trophic levels (fish), zooplankton has a crucial influence on the structure and function of lakes. The scientific literature shows that zooplankton is an effective indicator of eutrophication. However, according to the requirements of the Water Framework Directive, zooplankton is still not included as one of the biological components for assessing the ecological status of lakes. In Poland, the zooplankton-based method (ZIPLAs) has been developed to assess the ecological status of deep stratified lakes. Shallow lakes function differently from deep lakes, and literature data show that the response of zooplankton indices to eutrophication parameters is much weaker than in deep lakes. This paper presents the Zooplankton Index for Shallow Lakes’ Assessment (ZISLA), a new method for assessing ecological status based on zooplankton community structure. The ZISLA includes the body size index of Daphnia cucullata (BSI), the percentage share of high trophy-indicating rotifer species (IHTROT), the number of rotifer species (NROT), and the Margalef index (D). The ZISLA shows a strong, significant correlation with total phosphorus and total nitrogen (Spearman’s coefficient (R = −0.77, R = −0.74; p < 0.0001) and slightly weaker with Secchi disk visibility (R = 0.72; p < 0.0001). The ZISLA index shows a statistically significant good/moderate distinction for all water quality parameters.
Agnieszka Ochocka (Wed,) studied this question.