SPATIAL-SEASONAL DYNAMICS OF THE RIPARIAN ALGAL FLORA STRUCTURE IN THE AREA OF THE SEDNIV HPP IMPACT ON THE SNOV RIVER: PILOT STUDY

Abstract

Purpose of the work is to establish the features of seasonal transformation of the generic composition and abundance of algal communities of the Snov River in the zone of the Sedniv HPP impact.

Methodology. Material was collected in November 2024 and March 2025 in the HPP tailwaters in shallow waters (up to 0.5 m) within macrophyte communities. Samples were formed by combining 6 local samples. Laboratory processing was performed using light microscopy The frequency of occurrence of taxa was determined using a 4-point scale.

Scientific novelty. For the first time for small rivers of Polesie, the spatial-seasonal restructuring of the algal flora under flow regulation by a small HPP was detailed.

Conclusions. The channel dam of the HPP on the Snov River acts as a powerful ecological and hydrodynamic barrier for the development of microphytobenthos, the effect of which is most clearly manifested in the autumn period. Slowing down the current and water support to the HPP contribute to the eutrophication of shallow waters, the formation of phytocoenoses of the Glycerietum maximae association and the massive development of filamentous green (Zygnema, Ulothrix) and desmid algae. The hydrodynamic regime after the HPP (transitional flow, elimination of silt) leads to a twofold depletion of the algal flora, destruction of filamentous mats and leaves viable only a stable core of attached diatoms (Navicula, Gomphonema) in communities of the Caricetum ripariae association. In the early spring period, the flow factor of spring floods and low temperatures level the spatial differences caused by the HPP, shifting the phytobenthos of both areas into a depressed state dominated by cryophilic diatoms. It is substantiated that to establish accurate cause-and-effect ecological patterns in the zone of the HPP impact, future studies require transition from point scales to absolute quantitative indicators (algal abundance and biomass) with the involvement of a detailed hydrochemical analysis (nutrients and dissolved oxygen). This will allow the use of multivariate statistical analysis methods to build mathematical models and precise mathematical proof of the degree of hydrodynamic and chemical factors influence on the Snov River algal communities.