Self-Purification Capacity of Sevastopol Bay Ecosystems in Relation to Inorganic Forms of Nitrogen and Phosphorus from 2012 to 2020

I. V. Mezentseva1, E. E. Sovga1,*, T. V. Khmara2

1 Sevastopol Branch of the N. N. Zubov State Oceanographic Institute, Sevastopol, Russia

2 Marine Hydrophysical Institute of RAS, Sevastopol, Russia

* e-mail: science-mhi@mail.ru

Abstract

The paper uses the 2012–2020 joint oceanographic database of MHI RAS and SB FSBI SOI to estimate the self-purification capacity of Sevastopol Bay ecosystems in relation to biogenic nitrogen and phosphorus. The assimilation capacity and its specific value were calculated using the balance method. The paper estimates the average and maximum concentrations of inorganic phosphorus (PO4) and nitrogen (NO2, NO3, NH4), as well as the average and maximum rates and time of removal of these nutrients from the bay ecosystems. The paper shows changes in the percentage of forms of inorganic nitrogen (NO2, NO3, NH4) in the water area of all parts of Sevastopol Bay for two periods (1998–2012 and 2012–2020). These changes had a greater impact on the content of the reduced form of ammonium nitrogen which has increased in all ecosystems of the bay in recent years. Changes in the self-purification capacity of the bay ecosystems were manifested as a spread of data on the assimilation capacity of the study ecosystems in relation to nutrients. At the same time, the lowest self-purification capacity was observed for the ecosystem of the eastern part of the bay. The paper assesses possible causes of the observed situation, which are associated with changes in the wind regime over the bay water area in the last decade and the resulting formation of the system of surface currents. The surface currents in the bay under prevailing easterly winds were calculated using the computational modeling method. The paper shows that an increase in the frequency of such winds contributes to increased ventilation of the waters of Yuzhnaya Bay and a more intense input of pollutants in the westerly direction. The paper analyzes the reasons for deterioration in the self-purification ability of the eastern part of the bay in the last decade in relation to all inorganic forms of nitrogen and phosphates. It was shown that changes in the self-purification ability of ecosystems throughout the Sevastopol Bay waters were associated with an increase in the recreational load on the bay coast.

Keywords

Sevastopol Bay, biogenic nitrogen, biogenic phosphorus, ecosystem, self-purification ability, assimilation capacity, surface currents

Acknowledgments

The study was performed under state assignment of MHI RAS on topic no. 0827-2020-0004 “Coastal research”.

For citation

Mezentseva, I.V., Sovga, E.E. and Khmara, T.V., 2023. Self-Purification Capacity of Sevastopol Bay Ecosystems in Relation to Inorganic Forms of Nitrogen and Phosphorus from 2012 to 2020. Ecological Safety of Coastal and Shelf Zones of Sea, (4), pp. 101–115.

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