## 3 Results
The concentration of phosphates in atmospheric precipitation on 13 May 2016 was over 20 times higher than the annual value. The satellite image taken during this period showed the transfer of the air mass containing a large amount of dust aerosol [41]. An increase in the concentration of chlorophyll in several days after precipitations is seen in the distribution maps of chlorophyll-A (Figure 6), which was not accompanied by a lowering in water temperature (Figure 7). The rectangle shows the area of passage of dusty air masses with subsequent atmospheric precipitation, in which a change in the concentration of chlorophyll-A is observed. Figure 5: Change in the Black Sea surface temperature before (**a**) and after precipitation (**b**) 14 September 2010; ((**a**) time period 6 September 2010–13 September 2010; (**b**) time period 14 September 2010–21 September 2010). Figure 6: Concentration of chlorophyll-A in the surface layer of the Black Sea before (**a**) and after (**b**) precipitation 13 May 2016; (**(a)**) time period 8 May 2016–16 May 2016; (**b**) time period 16 May 2016–24 May 2016). Figure 7: _Cont._  
The graph in Figure 8 also shows the chlorophyll-A concentration in the surface layer of the Black Sea before precipitation and a few days after. As we can see, the concentration of the chlorophyll-A increased by \(\sim\)11%. Within a few days, the concentration of chlorophyll-a decreases, reaching background values due to removing of nutrients from the euphotic zone of this region. Because of its inner locations and surrounding by six countries, the Black Sea could be especially vulnerable to climate changes and anthropogenic influences. A characteristic feature of the Black Sea--existing strong stratification of the water column in the summer. Due to this stratification, the possibility of mixing between the bottom and surface layer decreases which leads to limited quantity of nutrients in the surface layer of the Sea. This restriction, in turn, results in decrease of the plankton community's capability to grow. Atmospheric precipitation and river runoff are the dominant sources of \"new\" primary production in the Black Sea under conditions of stable stratification in the spring-autumn period [44,45]. In addition to direct change in the nutrients concentration in the sea surface layer after atmospheric precipitation, the Redfield ratio at this water area also changes. Considering  
Figure 8: Graph of changes in the chlorophyll-A concentration in the Black Sea surface layer before and after precipitation 13 May 2016. Figure 7: Black Sea surface temperature before (**a**) and after (**b**) precipitation 13 May 2016; (**a**) time period 8 May 2016–16 May 2016; (**b**) time period 16 May 2016–24 May 2016). that it is not possible to carry out a comparative analysis of the nutrients content in the sea surface layer before and immediately after precipitation over the Black Sea, we carried out a similar work for the surface layer of the Sevastopol Bay. The results of the studies have shown that after precipitation, the value of the concentrations of nutrients in the surface layer of the bay in many cases was much higher than the background concentration and comparable to their concentration in areas subject to stormwater drainage and domestic wastewater runoff. However, several days after precipitation, nitrogen concentration, phosphorus, and silicon decreased linearly (Figure 9). Moreover, the content ammonium nitrogen reached the background level significantly faster than nitrates. This fact can be explained by the fact that that ammonium nitrogen is more available for consumption for some phytoplankton species. Table 2 shows the Redfield ratio calculated from the data on the background nutrients concentration in different seasons in the Sevastopol Bay, and the maximum values of this ratio calculated after atmospheric precipitation, deposited after dust transport. The influx of atmospheric precipitation containing significant amounts of nutrients into the bay can largely shift the Redfield ratio.