Trends in the interannual variability of nutrients in the northeastern part of the Black Sea according to ship observations for 2017-2021

Abstract

The results of long-term oceanological studies that were carried out as part of the Black Sea 2017–2021 complex scientific expedition and are devoted to the study of the coastal zone of the sea based on monitoring observations are presented. During all five years, a stable trend of a decrease in the content of silicon in the active layer of the coastal-shelf zone of the sea was observed. During the last 3 years, there has been an increase in the reserves of mineral phosphorus and a decrease in the content of mineral nitrogen. As a result of this variability in the content of phosphorus, nitrogen and silicon, during 2021, such stoichiometric relationships between them were established that a rare situation arose in the hydrochemical regime of the Black Sea waters. Phosphorus ceases to be the main element limiting the processes of development of biological communities, and among the three main biogenic elements, any of the parameters could act as a limiting factor or have a joint limiting effect on the development of photosynthesis.