The aim of the study is to assess the dynamics of phytoplankton biomass in the Karkinitsky Bay of the Black Sea, as well as the annual trend of its abundance based on satellite information. The article briefly describes the methodological steps for study the dynamics of phytoplankton biomass from satellite images, indicates the possible reasons for the formation of the eutrophication process in the Karkinitsky Bay, identifies and describes the optical categories of phytoplankton depending on its concentration, the reasons for the seasonal shift in the biomass of phytoplankton in comparison with other parts of the Black Sea by period from 19.02.2019 to 11.04.2020. The study allows to assess the possibilities of using the NDCI index for assessing the biomass of phytoplankton and make the conclusions on the process of eutrophication using the example of the Karkinitsky Bay. The scientific novelty of the work is the use of the NDCI index to study the dynamics of phytoplankton biomass in the Black Sea. As a result, several maxima and minima of phytoplankton biomass accumulation during the year (from 2019 to 2020) were identified and possible reasons for the observed results were described, the main of which can be considered a high anthropogenic load on the studied part of the Black Sea. © Published under licence by IOP Publishing Ltd.