Wet atmospheric depositions have been collected in a rural (Katsiveli) and urban (Sevastopol) location at the Crimean coast of the Black Sea from 2003 to 2008. Samples, 217 from Katsiveli and 228 from Sevastopol, have been analysed for inorganic fixed nitrogen (nitrate, nitrite, and ammonium). Data have revealed almost equal contributions of ammonium (44–45 %) and nitrate (52–53 %) and minor contribution of nitrite (2–4 %) for both rural and urban samples. The volume weight mean concentration of inorganic fixed nitrogen (IFN) in urban samples (2.51 mg N L⁻¹) is about 2-fold of that content in rural samples (1.16 mg N L⁻¹). Seasonal variations in volume weight mean monthly concentrations have been revealed for both locations with maximum concentrations in winter and minimum values in summer, but intra-annual variations are statistically significant for only urban samples. The average annual deposition of IFN with atmospheric precipitations on the surface of the Black Sea is about 0.31 × 10⁶ t N yr⁻¹ (0.75 t N km⁻² yr⁻¹), which is on average 39 % of the riverine input. It does vary in space and time. The relative importance of the atmospheric input increases from coastal to open areas and from winter to summer. Deposition of IFN with wet atmospheric precipitations proportionally increases the concentration of chlorophyll a, as it is traced from satellite data. The traced increase in the concentration of chlorophyll a has reached 1.5-fold for mesoscale processes. In case of individual rain events supporting up to 50–60 mg N m⁻², the influence of IFN deposition is up to 5 % at the north-western shelf of the Black Sea, where most of the river-born IFN is loaded. In the central areas of the sea, where the amount of IFN in summer is low, the contribution of individual rainfall can reach 35 %. The input of IFN to the Black Sea has potential to enhance 2-fold the level of primary production.

This paper focuses on the atmospheric dust transport effect on the changes in chlorophyll-A concentration in the Black Sea surface layer. In order to assess the input of nutrients with atmospheric precipitations at the Crimean coast of the Black Sea, the collected samples were analyzed for the content of inorganic nitrogen, phosphates, and silicon. The samples were taken into a wet-only sampler and into a permanently open one, to assess the effect of dust on the nutrients concentration in dry depositions. Cases of multi-fold excess of the nutrients content in the open sampler collected precipitation over that in the wet-only sampler were identified. For such high concentration cases, the 7-day back-trajectories analyses was carried out using the model of the international network AERONET and the HYSPLIT model. The results of our research showed that the influx of nutrients with the atmospheric depositions can result in increasing of chlorophyll-A concentration in 11–36% in the surface layer of the Black Sea. After atmospheric depositions, concentration of phosphates in the surface layer can increase more than five times compared with the background concentration. The increase of silicon concentration can reach 30%. The influx of atmospheric precipitation containing significant amounts of nutrients into the bay can shifts the Redfield ratio compared with background value up to three times.

Atmospheric depositions have been recently recognized as an important source of nutrients for off-shore marine systems, in line with the coastal input and physical exchange. The input of nutrients with atmospheric depositions can change their inventory and ratio in the euphotic zone, thus increase the rate of primary production and the type of predominant phytoplankton. The influence of atmospheric depositions, temporal variations of this influence and consequences of this deposition have been neglected. Monitoring of nutrients in atmospheric depositions of Crimea in 2015–2020 has allowed studying of multi-scale variations in their input to coastal areas and scaling the effects of this input. It has been found that the contribution of dry deposition in the total flux of nutrients is more significant for silicates and phosphates. Intra-annual variations in concentrations of nitrogen reveal a maximum in an urbanized area for the cold period of year, due to burning of extra fuel. On the contrary, increasing concentrations of nitrogen have been detected in a rural area in warm period. High values of concentrations of phosphorus and silica are typical for dry summer period and associated with dust transport from natural and anthropogenic sources. The N:P:Si ratio in the atmospheric depositions has been significantly shifted towards nitrogen as compared to the stoichiometric ratio. The results obtained in this work suggest that additional flux of nutrients with atmospheric depositions is minor at the annual scale, but it may change the local inventory and C:N:P ratio in the surface layer of the sea on a daily-time scale. The input of nutrients with atmospheric depositions can lead to additional (up to twofold) production of organic matter and result in additional oxygen consumption, when this surplus organic matter sinks and is oxidized, thus supporting suboxic conditions in near-shore areas.

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.