# Contribution of Atmospheric Depositions to Inventory of Nutrients in the Coastal Waters of Crimea
## 3 Results and Discussion
Atmospheric precipitations with extremely high concentrations of silica and phosphorus (even occasional events) can dramatically affect marine ecosystems, changing the structure of biological communities and the chlorophyll-a concentration. The input of dissolved nitrogen with heavy rainfall in summer may trigger phytoplankton blooms, resulting in high additional production of organic matter. Sinking detritus to bottom waters may result in seawater deoxygenation [40]. According to [16], the concentration of inorganic nitrogen in the river runoff of the Sevastopol region is 30,887 \(\upmu\)g L\({}^{-1}\), and phosphates is 695 \(\upmu\)g L\({}^{-1}\). This is mostly due to an influx of nutrients from the main regional rivers. The total runoff of these rivers is 245,858,106 m\({}^{3}\) year\({}^{-1}\) ([[https://nbcrs.org/regions/sevastopol/vodnye-resursylnalichie-rek-ozer](https://nbcrs.org/regions/sevastopol/vodnye-resursylnalichie-rek-ozer)]([https://nbcrs.org/regions/sevastopol/vodnye-resursylnalichie-rek-ozer](https://nbcrs.org/regions/sevastopol/vodnye-resursylnalichie-rek-ozer)) (accessed on 27 February 2023)). Based on these data, the annual load of nutrients into the coastal areas of Crimea is about 7594 t year\({}^{-1}\) for inorganic nitrogen and about 171 t year\({}^{-1}\) for inorganic phosphorus. The total load of nutrients with wastewaters to Sevastopol region bays [16] is about 1478 t year\({}^{-1}\) for inorganic nitrogen and 308 t year\({}^{-1}\) for phosphate. According to official data ([[http://www.depcxsev.ru/sevastopol_region.php](http://www.depcxsev.ru/sevastopol_region.php)]([http://www.depcxsev.ru/sevastopol_region.php](http://www.depcxsev.ru/sevastopol_region.php))), the area of the city's bays is 216 km\({}^{2}\). Then, the load of nutrients with atmospheric precipitations at the surface of the Sevastopol water area is about 94.11 t year\({}^{-1}\) for inorganic nitrogen and 1.27 t year\({}^{-1}\) for inorganic phosphorus (Table 4). The total input of inorganic nitrogen to the coastal waters of Sevastopol is provided for 82% by rivers, 16% by wastewater discharge, and 1% by atmospheric precipitations. For inorganic phosphorus, these values are 35.5%, 64%, and 0.5% by rivers, wastewater, and precipitation, respectively. These results suggest the very minor contribution of atmospheric depositions to the annual budget of nutrients in coastal waters. This leads to one general and widely accepted conclusion on the minor role of atmospheric deposition of nutrients in primary production of organic matter and an equally minor role of this contribution of nutrients to biogeochemical processes in coastal waters. However, atmospheric precipitations do not fall uniformly throughout the year, and the river runoff also varies significantly between seasons. Atmospheric precipitations often happen in strong short-term events at the time scale of hours to days. Therefore, the contribution of different sources of nutrients to their annual budget varies at a shorter time scale from hours to seasons. The Crimean river's runoff accounts for about 35% of its annual value in winter, about 44% in the spring, about 12% in the summer, and about 9% in the fall [41]. The flux of nutrients with wastewater within the year is rather uniform. The flux of nutrients with atmospheric precipitations is 93.5 t season\({}^{-1}\) for inorganic nitrogen and 1.41 t season\({}^{-1}\) for inorganic phosphorus in summer. These nutrients' fluxes are 113.9 t season\({}^{-1}\) and 2.14 t season\({}^{-1}\), respectively, in fall (Table 5). Thus, the contribution of atmospheric precipitations in the summer-fall period increases many-fold and from 1 to 7% for inorganic nitrogen in summer and even to 10% in winter. For inorganic phosphorus, the contribution also increases several-fold from 0.5 to 1.2% in summer, and further to 1.8% in winter.