# Contribution of Atmospheric Depositions to Inventory of Nutrients in the Coastal Waters of Crimea
###### Abstract  
Coastal zones are extremely vulnerable and, at the same time, anthropogenically pressed. Excessive enrichment of marine waters with nutrients and organic matter can lead to \"red tides\", oxygen deficits, decreasing assimilation capacity, etc. The purpose of this work is to study atmospheric precipitations as a source of nutrients directly affecting waters of the coastal areas of Crimea and, ultimately, strengthening eutrophication consequences. In 2004-2008, and from 2015 to present, samples of atmospheric precipitations have been collected at the Marine Hydrometeorological Station in Sevastopol. They have been analyzed for the content of inorganic nitrogen, phosphorus, and silica. For 2009-2014, direct measurements are unavailable and a previously retrieved multiple nonlinear regression equation has been used to estimate the concentration of inorganic nitrogen in atmospheric precipitations depending on meteorological conditions, including the number of precipitations, number of days without precipitations, relative air humidity, wind direction vectors, and air temperature. Data obtained in this study have revealed that atmospheric precipitations are one of important inputs of nutrients for local areas. Their relative contribution increases on the time scale of days, while the role of rivers remains the most important on the annual scale. The contribution of atmospheric precipitations to the inventory of nutrients becomes more significant in the summer, when seasonal stratification in the water column prevents vertical mixing of waters, and the ambient concentration of nutrients in the upper layer of water is minimal. atmospheric precipitation; nutrients; inorganic nitrogen; inorganic phosphorus; silica; sea water; coastal areas of Crimea +
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production and/or input of organic matter. The Black Sea is an inland and almost enclosed basin, which is particularly susceptible to the influence of riverine runoff [9]. The shelf and coastal area of this marine ecosystem is profoundly affected by increasing input of organic matter, nitrogen, and phosphorous compounds from the coast [10; 11]. Although the load of main rivers is located in the north-western part of the sea, small rivers carry about 15% of the Danube's discharge into other coastal areas and may result in high local eutrophication. The level of pollution of the Black Sea coastal waters from mainland is quite acute, especially near large cities [12]. The Chernaya river is one of the largest rivers of Crimea (Figure 1). To make the effect more profound, it discharges water into the most-inland part of the 8 km long Sevastopol Bay with a highly restricted water exchange with the open sea. It discharges 1.73 m\({}^{3}\) s\({}^{-1}\) of discharge on average [13], but it can be much higher in rainy periods. Estimates of the water balance of Sevastopol Bay have shown that the annual flow of the Chernaya River is about 70% of the volume of Sevastopol Bay [14]. Apart from fresh water, the Chernaya river delivers a lot of nutrients collected from farmlands up the river flow. It delivers 1000 tons of suspended matter on average, 52 tons of mineral nitrogen, and 6 tons of phosphorus annually [15]. This provides a significant impact on the state of coastal waters supporting high input of organic matter to the system due to primary production and resulting in seasonal hypoxia and anoxia in the bottom waters of the bay due to oxidation of produced and precipitated organic matter. Another recognized source of pollution in the coastal area of Sevastopol [16] is wastewater. There are 35 outlets of wastewater on the coast of the Sevastopol region, providing about 56 million m\({}^{3}\) year\({}^{-1}\) (1775 m\({}^{3}\) s\({}^{-1}\)) of wastewater of varying degrees of contamination. In addition to main outputs, there are 11 emergency wastewater outlets at the coast of Sevastopol. Storm water runoff in Sevastopol Bay contains up to 21.4-78.6 uM of nitrate, 4.28-1222 uM of ammonium, and up to 37.7-101 uM of phosphate [16].