Jana Paidere, Agnija Skuja, Laura Grīnberga, Dāvis Ozoliņš, Ilga Kokorīte, Aija Brakovska, Rasma Tretjakova
Seasonal zooplankton community structure in the littoral and pelagic zones of a shallow lake
Abstract The largest part of shallow lakes in Latvia, including the focal Lake Saukas, corresponds to the European Union importance habitat
Natural eutrophic lakes with Magnopotamion or Hydrocharition-type vegetation. The state of these Latvian lakes is assessed as unfavourable-inadequate, particularly regarding their structure and function. Therefore, the study aimed to determine the seasonal structure of functional groups in the zooplankton community, as an important part of freshwater food webs, in shallow Lake Saukas in relation to the littoral and pelagic zones. The study was conducted in the littoral and pelagic zones from May to November in 2020. The basic structure of zooplankton in Lake Saukas was formed by functional groups of cladocerans and copepods, with a low biomass (ranging from 0.81 to 0.26 g m
-3). Life history effects, seasonal succession, top-down control, and lake trophic state are possible contributors to changes in zooplankton functional groups in Lake Saukas. The lowest rotifers guild ratio values were recorded in pelagic zones, dominated by microfilters, and the highest in littoral zones, dominated by raptors. Alterations in the guild ratio of rotifers were driven by the season and by competition with cladocerans in the pelagic zones. The zooplankton communities resemble a meso-eutrophic or slightly eutrophic state in Lake Saukas, as indicated by their low biomass and abundance and their diverse functional structure. These results improve our understanding of the functional structure and productivity of the shallow Lake Saukas ecosystem, thereby supporting the development of sustainable ecosystem-based management strategies and fisheries in the lake.
Doi https://doi.org/10.35513/21658005.2026.1.3 Keywords Zooplankton; functional groups; Rotifera guild ratio; lake trophic state
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