Species structure of zooplankton communities in the thickets of higher aquatic plants in a small river (on the example of the river Serezha of the Nizhny Novgorod region)

Small rivers have great biotopic diversity due to the development of different types of thickets of higher aquatic plants in the coastal area. Zooplanktocenoses of small rivers are less studied than those of lakes. In connection with this, the study of the species structure of zooplankton communities in the macrophytes thickets of small rivers is relevant. This paper describes the species structure and quantitative development of zooplankton communities in the medial zone and in thickets of higher aquatic plants of the small river Serezha, Nizhny Novgorod region. On the basis of hierarchical clustering in the medial zone of the river, two zooplankton communities were distinguished: the river section and the transitional one. The differences in the species structure of the zooplankton communities belonging to different types of macrophyte thickets and the medial zone of the river are shown. It was established that a high species richness and quantitative development of zooplankton communities was formed in the thickets of higher aquatic vegetation. In macrophyte thickets of various morphological structure differences in the quantitative development and the ratio of taxonomic groups of zooplankton in terms of abundance and biomass were established. It was shown that macrophyte architectonics and density of thickets had the greatest impact on the overgrown zooplankton. In dense thickets of immersed plants, maximum values of the zooplankton abundance and biomass are noted. According to the redundancy analysis, the effect of abiotic and biotic environmental factors on the species structure of zooplankton communities in the medial and ripal of the river is shown. In the medial zone of the river, the rate of flow and the pH of water had a significant effect on zooplankton. The river flow rate and water pH have the greatest impact on the species structure of zooplankton communities in the medial zone of the river, but the projective plant cover - in the coastal area.