Basic aspects of the biogenic elements balance in the Azov Sea

This article presents the basic aspects of the dynamics of biogenic elements in the Azov Sea, based on literature data and our field research, conducted recently in different seasons of the year from 1998 to 2018. Correlation relationships of the main factors, affecting the change in the content of biogenic salts, are presented, and seasonal aspects of the dynamics of the mineral forms of nitrogen, phosphorus and silicon are given. It has been established that the Taganrog Bay is affected by the Don River flow to a greater measure, and in the sea, the significant role in the dynamics of biogenic elements is played by intrabasin processes. The importance of the river flow influence is shown by the supply of biogenic elements to the Taganrog Bay, in which not only the volume of river flow but also the general antrhopogenic pressure on the Lower Don and the Taganrog Bay area are crucial factors. Bottom hypoxia in the summer season plays a prominent role in enriching the water column with phosphates and ammonium nitrogen. In estimation of the dynamics of biogenic elements in the Azov Sea, the seasonal processes of mineralization of organic substances, the rate of recycling of biogenic compounds, life cycle of phytoplankton, wind speed over the sea surface, formation of density and oxygen stratification of water masses, water exchange with the Black Sea, bottom sedimentation, outwashing from rock material, and introduction of elements with atmospheric precipitations should also be taken into account. All factors, affecting the change in the concentration of mineral forms of nitrogen, phosphorus and silicon in water, are given in the form of flowcharts.