Ecological Systems and Devices Annotation << Back The Influence of River Runoff of Different Trophic Levels on Microplankton of the North-Eastern Part of the Black Sea Mosharova I.V., Mosharov S.A., Dallakyan G.A. The influence of river runoff on the variability of fluorescent parameters of the abundance and functional activity of phyto- and bacterioplankton in the plumes of the Kodor and Tuapse rivers in the northeastern Black Sea has been studied for the first time. It has been established that the plumes of rivers of different trophic status differed statistically reliably in all the parameters studied. We believe that the increase in the functional activity of microplankton at the boundaries of river plumes, as well as the change in the morphological composition of bacterioplankton (from the dominance of rod-shaped forms in river waters to typical marine bacterioplankton consisting mainly of small cocci at the boundaries of plumes) may indicate the enrichment of river runoff areas with easily oxidizable organic matter, formed, among other things, due to the death of freshwater species of phyto- and bacterioplankton when they enter the marine environment. The effect of stimulating the metabolic activity of microplankton was more pronounced in the plume of the mesotrophic river Tuapse. Keywords: bacterioplankton, chlorophyll a, microplankton, river plumes, Black Sea. DOI: 10.25791/esip.8.2025.1541 Pp. 46-58.