Experimental Assessment of Epipelon Responses to Phosphorus Limitation in a Eutrophic Lake

ABSTRACT In a mesocosm experiment conducted in an urban lake, we evaluated the responses of algal and cyanobacterial communities in the epipelon to increased P limitation in the water column under eutrophic conditions. Water and sediment samples were collected on days 3, 10, 17, 27, and 60 of the experimental period. Environmental conditions in the treatment with N addition were characterized by an increased N:P ratio and N availability, accompanied by a transient decrease in phytoplankton biomass during the initial phase. Algae and cyanobacteria in the epipelon responded to increased P limitation caused by nitrogen enrichment, increasing the total biovolume. Changes in composition and descriptor species were associated with the P‐limiting condition, which favored species with luxury P uptake. Our results suggest that the positive response of the epipelon was driven by changes in limitation potential, nutrient concentration, and local environmental conditions, rather than phytoplankton dynamics alone. Species with luxury P uptake, including cyanobacteria, were favored under an increased N:P ratio. This study advances our understanding of epipelic community structure in eutrophic systems and highlights the importance of benthic–pelagic interactions under nutrient imbalance scenarios, showing that epipelic communities can respond directly to environmental changes in the water column.