V. A. Senkevich’s research while affiliated with Penza State University and other places

This review summarizes information on the main negative factors affecting the state of floodplain water bodies ecosystems, describes the most common consequences for abiotic and biotic processes, and suggests possible ways to conserve these ecosystems. Evidence of the negative impact of hydraulic construction, embanking of floodplains, channelizing of rivers, agriculture, and other anthropogenic impacts is presented. A special role is played by climate change, which leads to a decrease in flood inundation, drying and overgrowing of water bodies, and their eutrophication. The authors suggest criteria to choose correct indicators that can testify not only to special stages of water body succession (e.g., vegetation) or its trophic status (zooplankton), but also to the long-term effects of anthropogenic and climatic changes. As a recommendation, it is proposed not to consider water bodies separately, but to assess the whole waterscapes and use the change in β-diversity as an indicator. Further conservation strategies can be based on the approaches of the Red List of Ecosystems of the International Union for Conservation of Nature and Natural Resources (IUCN), which will help to draw attention to the problem. The key role for the conservation of floodplain water bodies should be played by territorial protection measures, up to the development of a separate category for small water bodies.

Background. Urban ponds are subject to a strong anthropogenic load and, therefore, are always in the focus of attention of researchers. The pond at the clinical hospital No.6 in Penza was created in 1983. At the moment, cleaning measures are planned on this reservoir. Previously, for a long time (2010–2014), we have been studying the zooplankton community of Arbekovsky Pond. Due to the fact that large-scale work is expected in the reservoir, studies of these hydrobionts have been resumed.The purpose ofresearchistostudythe long-term and seasonal dynamics of the structural parameters of the zooplankton community in the Arbekovsky Pond and assess its condition before the start of cleaning measures. Material and methods. Samples for zooplankton research were taken in 2010– 2013 in May, early and mid-June, July and August (three samples each), in 2014 in May, July and August (nine samples each) and in 2020–2021. monthly from May to September (four samples each).A total of 139 samples were analyzed. Results. During seven years of research, 147 species and forms of zooplankton were recorded in Arbekovsky Pond.Of these, eleven taxa form a permanent species composition for 7 years of observations of the community.The species of rotifers Synchaeta kitina was recorded for the first time for the Penza region and replenished the complex of "northern invaders" in our region.The zooplankton community of the Arbekovsky Pond is sensitive to natural and anthropogenic impacts. The abundanceof species of the zooplankton community was the highest in hot and dry 2010, and the diversity of the community – in 2014, when its development was more calm and harmonious. In 2010–2014 Rotifers had a high abundance, and in 2020–2021 – copepods.Rotifers and copepods breathe through their entire body surface rather than through their gills, so they can more successfully withstand hypoxia.The structural parameters of the zooplankton community in recent years indicate the accumulation of organic matter in the water and the violation of the oxygen regime in the pond. Conclusions.The results of the study of the current state of the zooplankton community of the Arbekovsky Pond confirm the need for cleaning this reservoir with subsequent regulation of the hydrological regime.

The structure and dynamic of mollusk communities, as well as environmental factors influencing them, were analysed under conditions of small oxbow lakes in the forest-steppe zone (a case of the Khoper river valley, Penza region). 19 species of mollusks were found in the studied water bodies. The oxbows were characterized by relatively low alpha-diversity (number of species 4 ± 2) with relatively high beta-diversity (Jacquard index 0.26 ± 0.18), which is typical for floodplain ecosystems. Lake communities was dominated by Planorbis planorbis (40 %), Lymnaea stagnalis (15 %), Anisus spirorbis (14 %), Lymnaea saridalensis (9 %), Anisus vortex (8 %). The results of our analysis showed that the group of factors that determined the type of water body (stability, light intencity, water temperature, oxygen concentrations) had the greatest impact on the structure of malacocenoses. The seasonal dynamics of mollusk communities was determined by the number of adjoining water bodies, water temperature, and dissolved oxygen concentrations. The number of adjoining oxbows influenced species diversity the most, as well as the total number and biomass – isolation was more favorable for mollusk communities. The factors influencing the highest number of mollusks species (seven) were the light intencity and the presence of fish. Other significant factors were the stability of lakes (five species of mollusks), the number of oxbows and the transparency of the water (four species). Aquatic vegetation positively correlated with only one species – Anisus vortex. Our data suggest that the presence of fish could influence the abundance of Lymnaea saridalensis. The mollusks themselves, apparently, had a positive effect on the number of leeches in water bodies. The most sensitive to the factors were Lymnaea stagnalis, Lymnaea saridalensis, Aplexa turrita, Anisus spirorbis and Anisus leucostoma, the most tolerant were Bathyomphalus crassus, Anisus vortex, Planorbis planorbis, Planorbarius corneus

The aim of our study was to identify the main abiotic factors that influence the biodiversity of forest-steppe oxbows in limnophase. Experiments were performed in 2016–2017 in Penza oblast, Central Russia. In addition to disturbed water exchange, isolated oxbows experienced such human influence as logging and plowing on watersides, and the construction of roads and mounds. Under those conditions, some water bodies became unstable and temporal, while others remained stable and were relatively unaffected. Higher light intensity in unstable oxbows led to higher plant diversity because of the mass occurrence of helophytes. However, the diversity of hydrophytes in stable oxbows remained higher, which contributed to higher vegetation coverage. This resulted in increased zooplankton diversity, which was also influenced by lower fluctuations in water level and oxygen level. Disturbed water regimes impacted organisms with a full aquatic life cycle (phyto- and zooplankton, fish). The diversity of unstable oxbows decreased due to their isolation from the river and from drying. The absence of fish may positively affect the abundance and biomass of benthos; however, we found no influence on zooplankton. Instability and high fluctuations in water level may lead to the high diversity of organisms that spawn in water. The higher diversity of benthos may also be influenced by the abundance of amphibian larvae which are a necessary food resource. In addition to predation, amphibians are at risk of mass larval mortality because of drying. Although the degradation of oxbows in limnophase is an undesirable consequence of anthropogenic impact, the coexistence of all types of oxbows is necessary to conserve the freshwater biodiversity of forest-steppes.

In the zooplankton community of the small river Elshanka, Sura River basin, a right-bank tributary of Volga River, the rotifer, aspelta angusta Harring et Myers 1928 was found, a species recorded earlier in Russia only in small rivers of the basin of Lake Onega. Ecological preferences of the species were revealed: water temperature 18°C, pH 7.8, and structural parameters of the rotifer community determined.