Dmitriy Evgenievich Gavrilko

Species and functional diversity are essential frameworks for analyzing changes in planktonic communities. In lakes and rivers, macrophytes within the coastal zone are a primary determinant of zooplankton community structure and function. This study investigated the influence of various macrophyte beds in the littoral zones of lakes and river estuaries on the species and functional diversity of zooplankton communities. Our analysis revealed that among the species diversity metrics, only zooplankton species richness notably demonstrated a clear relationship with macrophyte type and their projective coverage. The highest richness was observed in mixed and submerged macrophytes due to the peculiarities of their morphological structure. Functional diversity indices—functional richness, functional evenness, and functional divergence—had a strong association with diverse macrophyte belts. The extent of these differences in zooplankton species and functional diversity is further amplified by a greater representation of diverse macrophyte belt types within the littoral zone. Macrophyte thickets consistently demonstrated increased species richness, functional richness, and functional divergence in zooplankton communities compared to open water zones, with mixed and submerged macrophytes exerting the most pronounced impact on diversity. These results underscore that the diverse structures of macrophytes contribute significantly to variation in zooplankton diversity in coastal areas. Consequently, functional diversity indices prove to be more effective tools than traditional species diversity indices for assessing changes in planktonic communities along spatial gradients.

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 a) 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.

The distribution and ecological preferences of the rare water flea Ovalona karelica (Stenroos, 1897) (Crustacea, Branchiopoda, Cladocera) were analysed for the first time for European Russia. The species was found in different types of waterbodies, such as floodplain lakes of the Kerzhensky State Nature Biosphere Reserve, Nizhny Novgorod City and mouths of rivers inflowing into reservoirs. Ovalona karelica inhabits waters with wide ranges of pH, salinity, oxygen content and trophicity. Development of semi-submerged macrophytes (Stratiotes, Hydrocharis, Salvinia) is the main factor influencing occurrence of the species and its abundance.

Aquatic macrophytes in the littoral zone of lakes act as a powerful environmental factor, shaping the spatial distribution of aquatic organisms. The study examined the distribution patterns of zooplankton communities across the transverse profile of macrophyte beds in the littoral zone of small lakes in the Nizhny Novgorod region. It was found that in the studied biotopes, macrophyte beds altered several water parameters and created their gradient. The analysis revealed that, from the shoreline helophyte and mixed vegetation toward the open water, zooplankton communities exhibited a gradual shift in dominant and subdominant species, a decrease in the proportion of cladocerans, and an increase in rotifers. The type of biotope had the greatest influence on the species structure of zooplankton communities. The study also analyzed the preference of certain zooplankton species for macrophyte beds of different life forms. A decline in species richness and zooplankton biomass was observed at the edge of vegetation near the open water. It was concluded that the succession of plants from different ecological groups along the transverse profile of the macrophyte zone drives changes in environmental factors and planktonic invertebrate communities in an ecocline-like manner.

Freshwater zooplankton is an important component of the ecological communities of inland water bodies. It acts as an important part of the food web and participates in the self-purification processes of aquatic ecosystems. To study the abundance and distribution of species, a sampling event dataset was compiled and then published through GBIF. The aim of the work was to describe the current zooplankton fauna (Rotifera, Cladocera and Copepoda) and its abundance, based on a recently published dataset. The research was conducted from 2015 to 2022. Zooplankton samples were collected by vertical towing a plankton net (70 μm mesh) from the bottom to the water surface or by filtering through a net, the water being collected with a measuring bucket. The samples were concentrated to 100 ml and fixed with a final concentration of 4% formalin solution. For each sampling event, the coordinates of the location, number of individuals and date were recorded. The dataset contains information on 259 taxа, including 257 species and subspecies of zooplankton from 36 families found in the tributaries of the Cheboksary Reservoir. The families Chydoridae (35 species), Brachionidae (31) and Cyclopidae (27) were the most species-rich. Four invasive species were found: Kellicottia bostoniensis (Rousselet, 1908), Acanthocyclops americanus (Marsh, 1893), Ilyocryptus spinifer Herrick, 1882 and Thermocyclops taihokuensis Harada, 1931.

The gradients of hydrological, hydrophysical, and hydrochemical conditions form the transition zones in river mouth areas. These areas are considered ecotones in the presence of the edge effect. Our research aimed to identify the main patterns in the structural organization of zooplankton communities in different types of river mouth areas in lowland reservoir tributaries within the Middle Volga basin. A cluster analysis was performed to structure and determine the zooplankton communities. The identified zooplankton communities were characterized by the noticeable heterogeneity in the species structure. We analyzed the spatial distribution of the structural indicators of zooplankton communities and, on the basis of RDA, determined the factors that significantly affect the organization of the ecotone community. An ecotone was found in all types of river mouth areas where the highest density, biomass, diversity, species, and functional richness of zooplankton were noted, as compared to bordering zooplankton communities. As the morphological structure of the mouth areas became more complex, the values of the main structural parameters of zooplankton communities increased. It was demonstrated that conditions in the ecotones are favorable to the development of zooplankton alien species. The major factors determining the species structure of the ecotone zooplankton community were water electrical conductivity (R² = 21.07%, p-value = 0.001), dissolved oxygen content (R² = 10.33%, p-value = 0.003), and water transparency (R² = 9.77 %, p-value = 0.001).

The investigation presents the results of studies of plankton in the area of the middle course of the riverSerezha in 2019. The floristic diversity of phytoplankton was characterized, its abundance and biomass were estimated, and the change in the morpho-functional groups of phytoplankton along the river was shown. The influence of some physical factors on the development of planktonic algae is considered. The water quality of this section of the watercourse was assessed by phytoplankton biomass, as well as using the community index and the Pantle-Bucksaprobity index.