Based on data from long-term observations (1983–1995, 2001–2021), the influence of phosphorus intake and climate variability on the interannual dynamics of the chlorophyll a concentration in waters of the eastern Gulf of Finland was analyzed. During the study period, the concentration of chlorophyll, as well as the North Atlantic oscillation index (NAO), varied widely with a weak tendency to decrease their values. It was found that in 1983–1995, the chlorophyll concentration positively correlated with phosphorus intake and the NAO index. Since 2001, there has been no correlation with these factors, probably due to changes in the hydrochemical and hydrobiological regime in the bay. It is concluded that in recent decades, the interannual dynamics of chlorophyll a in the eastern Gulf of Finland has depended both on the nature of the internal (phosphorus intake from the bottom) and external (phosphorus intake from river runoff) loads on the waterbody, as well as on climate variability.
O. B. Maximova (Sun,) studied this question.