Influence of Atmospheric Precipitation and Surface Runoff on Phytoplankton Characteristics in the Northern Part of the Black Sea

The joint dynamics of phytoplankton parameters (primary production, specific growth rate, and biomass) and amount of precipitation in coastal regions and on the shelf in the northern part of the Black Sea in 1998–2015 are studied based on satellite data (SG) (GPCPMON) GPCP Version 3.2, TRMM TMPA (3B42RT), SeaWiFS from 1998 to 2010, MODIS-Aqua from 2002 to 2015, and MODIS-Terra from 2000 to 2015. The phytoplankton parameters are calculated according to earlier developed models. Their monthly average values, as well as bi-weekly and daily values of atmospheric precipitation are assessed. As a result of the study, insignificance of the part of atmospheric precipitation in the variability of phytoplankton parameters on vast water areas and long time periods is revealed. It sometimes increases to 30% in offshore areas in the presence of influxes of large rivers. The effect of atmospheric precipitation on the biological productivity of phytoplankton in small bounded water areas and short time periods is more pronounced. According to our data for 18 years, a correlation between the specific growth rate and precipitation on the Black Sea shelf is stronger in winter than in other seasons; the correlations of biomass and primary production of phytoplankton with atmospheric precipitation are less pronounced. The specific growth rate of phytoplankton correlates with precipitation stronger than other phytoplankton parameters under study. An increase in the amount of precipitation over previous level with the monthly averages above 0.6 mm/day increases the specific growth rate or maintained it at the same level. The increase in the specific growth rate is not the same everywhere and not proportional to the amount of atmospheric precipitation. This witnesses the influence of many factors on the phytoplankton parameters; however, precipitation could be an additional stimulating factor.