Relationship between the quantitative development of phytoplankton and environmental factors in lakes of different trophic status in the Belarusian Lakeland

Аннотация

This study examined 11 lakes of the Belarusian Lakeland, encompassing the range from mesotrophic lakes with oligotrophic features to highly eutrophic systems, to evaluate the impact of abiotic factors on the quantitative development of phytoplankton. Sampling was carried out during the growing seasons of 2023–2025 using standard hydrobiological and hydrochemical methods. Phytoplankton biomass showed an increase from 0.46–0.85 mg/L in mesotrophic lakes with oligotrophic features to 22.7–46.75 mg/L in hypereutrophic lakes. Among environmental factors, nitrogen compounds exerted the strongest influence, particularly nitrate nitrogen (r_s up to 0.7; p < 0.001), while the role of total phosphorus was less pronounced. The analysis did not consider the concentration of phosphate ions (P–PO₄) because it was mostly below the analytical detection limit, and the number of measurements with non-zero values was insufficient for statistically robust conclusions. Redundancy analysis (RDA) revealed that the combined effect of environmental factors explained up to 55% of the variation in phytoplankton, with the trophic gradient being the dominant driver. Both nitrate and ammonium nitrogen contributed significantly to phytoplankton development; however, the effect of nitrate nitrogen was more pronounced. This was likely due to the rapid uptake and oxidation of NH₄⁺ under conditions of high oxygen concentration, which complicates the evaluation of its impact, whereas nitrate was consumed more slowly, allowing for a more reliable statistical evaluation of its role. The obtained results refine our understanding of the role of different nitrogen forms in shaping the productive state of lakes and may be applied in assessing their trophic status.