Dynamics of chlorophyll a concentration in the Black Sea on satellite data

Abstract

The use of satellite data to study the chlorophyll a dynamics, in contrast to contact methods, allows carrying out large scale research with high frequency of measurements. Such observations were carried out in the Black Sea offshore and inshore areas from 1998 to 2015. They made it possible to estimate the annual and interannual chlorophyll a dynamics in the surface layer and to reveal the periodicity, intensity, and duration of mass development of algae. In the western and eastern cyclonic gyres as well as in the shelf zone off the Crimean and Caucasus coasts, annual chlorophyll dynamics had the same pattern as that repeating year after year. From August-September to April-May of the next year the variation of chlorophyll in most cases corresponded to normal distribution and had a form of a bell-shaped curve with maximum observed in December-January. During autumn period, the chlorophyll concentration gradually increased with water cooling and seasonal pycnoclyne weakening. In winter the chlorophyll concentration decreased due to increase of mixed layer depth. Spring phytoplankton intensive development was observed every year when convective mixing weakened and stability of water column increased.