The main aim of the study was to analyze diurnal changes in the composition and dynamics of the cladoceran community among three stations located along a horizontal transect that included the central part of a Myriophyllum verticillatum bed at the perimeter of a macrophyte stand and the open water zone of neighboring vegetated stations. Typically littoral species distinctly dominated the material examined. Ceriodaphnia quadrangula significantly influenced the total crustacean community. The maximum abundance of littoral species was noted in the middle part of the plant stand while the minimum was in the open water. These species revealed a similar pattern of diurnal distribution, irrespective of the station, with the highest numbers at night and the lowest during the day and morning. A similar pattern of diurnal distribution was also observed for pelagic species that exhibited significant differences in the open water zone between the day (the lowest numbers) and night (the highest) samplings. It was suggested that the diurnal distribution of cladoceran representatives between the macrophyte bed and the open water zone of Lake Wielkowiejskie might have been influenced by young fish predation (pelagic species) and by typical adaptations of particular species to living within the heterogeneous habitat of a macrophyte stand (littoral species).
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The main aim of this study was to analyze the diel distribution of zooplankton communities within the zones of Nymphaea albae, Myriophyllum verticillatum, and Typha angustifolia, and, compared to that, in the open water area of a lake. It also aimed to analyze the relationship between zooplankton densities and the concentration of physicochemical factors and chlorophyll a content. A total of 149 zooplankton taxa were noted, and, despite the narrow range of the research in the analyzed lake, some rare species were noted, among which two - Colurella sinistra and Lecane inopinata – were recorded for the first time among Polish fauna. The rush zone was taxonomically the richest, while the open water area was the poorest. The highest number of individuals was observed in the Myriophyllum bed, while the lowest was noted in the zone dominated by Nymphaea alba. The highest densities of zooplankton occurred at dusk, while the lowest occurred during the day, irrespective of the sampling station. Because Lake Wielkowiejskie is a shallow and macrophyte-dominated water body, the differences in the diurnal distribution of zooplankton communities may suggest horizontal migrations between the pelagic zone and the phytolittoral, as well as between particular macrophyte stands. A positive correlation between the densities of some zooplankters and the concentration of chlorophyll a was found, while a negative relationship with the concentration of nitrites was recorded for Lecane quadridentata and Alonella nana.