Abstract <p>Changes in the qualitative and quantitative composition of zooplankton communities along the cross-sectional profile of higher aquatic plant thickets in the estuaries of the Vetluga and Sura tributaries of the Cheboksary Reservoir are considered. The gradient of the main abiotic and biotic parameters (temperature, pH, transparency, turbidity, content, total nitrogen, phosphorus, and chlorophyll <i>a</i>) is revealed in macrophyte thickets. The changes in the species composition of zooplankton communities are shown along the gradient from helophyte beds to pleustophyte beds to open water. An increase in the proportion of rotifers and a decrease in the proportion of cladocerans in the direction from helophyte thickets to open water is recorded. It is shown that the habitat type had the greatest influence on the species structure of zooplanktocenoses. It is concluded that the change of ecological groups of plants along the transverse profile of the thicket zone determines changes in environmental factors and communities of planktonic invertebrates by the type of ecocline.</p>