Реконструкция величин фотосинтеза в Онежском озере по концентрации хлорофилла а

Abstract

Phytoplankton photosynthesis in Lake Onego was measured in 1989-2006. An attempt was made to calculate photosynthesis by daily assimilation numbers and chlorophyll a concentration measured in 2007-2021 to supple-ment data on the primary production. Daily assimilation numbers were calculated by simultaneously measured photosynthesis and chlorophyll in 1989-2006 for different areas and seasons of a limnically complex water body. A comparative statistical analysis of the size-structural characteristics of phytoplankton in 1989-2006 and 2007-2021 was performed to assess the possibility of using the obtained assimilation numbers to restore photosynthesis values. Comparison of the average cell volume for the phytocenosis and the ratio of diatoms and smaller non-diatoms showed their similarity in both periods in the main water area of the lake. Only in the central sector of Kondopoga Bay, which has been influenced by biogenic loads from the trout farms since the 2000s, the average cell volume decreased significantly and the proportion of diatom plankton also decreased. Photosynthesis was not calculated for this sector. The calculated assimilation numbers were similar for almost the entire water area of the lake. The maximum daily values were observed in summer with medians from 11.8 to 18.4 µg C/µg Chl in different parts of the water body. In Kondopoga Bay, which during both study periods was experiencing a biogenic load of wastewater from the pulp and paper mill, their median values in summer reached 40.3 and 29.6 µg C/µg Chl day–1 in the top and open parts, respectively. It was possible to restore 197 values of photosynthesis by chlorophyll a measured in 2007-2021and by the calculated assimilation numbers in the surface water layer of different areas in Lake Onego in different seasons.