Trends in Changes in Primary Phytoplankton Production According to Remote Sensing Data in the Deep-Sea Region of the Black Sea for 1998–2015

The analysis of long-term seasonal changes in the concentration of chlorophyll, the maximum rate of phytoplankton photosynthesis and water temperature in the surface layer of the open waters Black Sea from 1998 to 2015 has been carried out. The trends of these indicators were assessed. For the research, we used the data of satellite observations SeaWiFS and MODIS-Aqua, MODIS-Terra. Typical positive temperature trends of 4 % in the deep-water western part of the sea. An annual temperature rise in deep-water areas was noted in the western cyclonic circulation by 0.038 °C. According to average annual data in other areas, no increase was found. The increase was mainly due to the winter season. Negative trends of primary phytoplankton production within 16.4–18.6 % of the initial level according to average annual values throughout the deep-water area. Significance level — p < 0.1. A decrease in primary production was observed in the summer. There were no statistically significant directional changes in chlorophyll concentration based on averaged data over 18 years. In different parts of the deep-sea area, the direction of interannual and seasonal changes in all indicators was similar. The emerging trend towards a decrease in phytoplankton productivity in recent years may lead to a restructuring of the phytoplankton community.