Distribution of picoplankton and detritus in the lower course of the Kama River

Abstract

The distribution of picoplankton and detritus in the lower course of the Kama River in 2009, 2012, 2016 and 2020 was analyzed. The abundance (1.5-6.7 × 106 cells mL−1) and biomass (25-173 ug C L−1) of picoplankton corresponds to the mesotrophic level. The abundance and biomass of the heterotrophic picoplankton increases from spring to autumn, the autotrophic picoplankton has maximum in August. The amount (17-1367 × 103 particles mL−1) and mass (0.1-62 μg C L−1) of picodetritus varies greatly from station to station without clear patterns, but basically its mass is higher at coastal stations. Heterotrophic picoplankton prevails in picoseston structure; the average APP and picodetritis contributions are comparable, with little excess of picodetritus. The structure of the picoseston varies significantly depending on the season and the riverbed or the coastal location of the station. The amount of nanodetritus is very high (up to 229 × 103 particles mL−1 and 662 μg C L−1), and it varies slightly both in space and in time. Its mass is almost always several times higher than the biomass of picoceston Most likely, nanodetritus is one of the main factors affecting the plankton of the lower course of the Kama River.