Inorganic Forms of Nitrogen in the Deep Part of the Black Sea Based on the Expeditionary Data, 2016–2019

S. I. Kondratev✉, A. V. Varenik, N. A. Orekhova

Marine Hydrophysical Institute of RAS, Sevastopol, Russian Federation

✉ e-mail: skondratt@mail.ru

Abstract

Purpose. The purpose of the study is to describe quantitatively the structure of vertical distribution of the nitrogen inorganic forms, namely nitrites, nitrates and ammonium ions, at the present post-eutrophication period of the deep-sea ecosystem evolution in the Black Sea based on the field data obtained in 2016–2019.

Methods and Results. The data obtained in the Black Sea within the economic zone of Russia in 2016–2019 by the scientists of Marine Hydrophysical Institute were used. At more than 200 deep-sea stations, a cassette of 12 bathometers (Seabird-Electronics CTD-instrument) was applied for taking hydrochemical samples at certain isopycnic surfaces, usually at σt = 16.30; 16.25; 16.20; 16.15; 16.10; 16.05; 16.00; 15.95; 15.90; 15.80; 15.50, 14.0 kg/m3. Such a scheme permits to determine the suboxic zone locations (including its upper boundary), the depth of hydrogen sulfide formation, and also to study in detail the changes in the nitrogen forms during transition from the oxic conditions to the anoxic ones.

Conclusions. At the present post-eutrophication period of the deep-sea ecosystem evolution in the Black Sea, qualitative characteristics of the vertical distribution of inorganic nitrogen forms correspond to the already known features. The quantitative ones are characterized by the following values: from the surface to the oxicline onset near the isopycnic surface σt = 14.5 kg/m3, the contents of nitrites and nitrates were at the level 0.06 μM and 2–3 μM, respectively, and the ammonium concentration did not exceed 0.6 μM. As for the nitrite vertical profiles, two maximums are noted at the isopycnic surfaces σt = 14.0 kg/m3 and σt = 15.9 kg/m3; the value of the second peak does not exceed 0.07 μM. The nitrate vertical profiles are characterized by a maximum within the range of isopycnic surfaces σt = 15.2–15.5 kg/m3; its value reached 4–5 μM. The ammonium considerable concentrations were recorded at the isopicn σt = 16.0 kg/m3, after which the ammonium content monotonously increased with depth reaching the value 96 ± 5 μM at the 2000-meter depth. The molar ratio NH4+/H2S near the upper boundary of the hydrogen sulfide zone was 0.58 that indicated a significant equivalent excess of ammonium as compared to the theoretical stoichiometric value 0.30. At greater depths where the H2S concentrations are high (≥ 380 μM), it decreased to 0.25 and approached the theoretical value.

Keywords

Black Sea, hydrogen sulfide, nutrients, inorganic forms of nitrogen, vertical profile, field data

Acknowledgements

The investigation was carried out within the framework of the state assignments No. 0555-2021-0004 “Fundamental studies of the oceanological processes which determine state and evolution of the marine environment influenced by natural and anthropogenic factors, based on the observation and modeling methods” and FNNN 0555-2021-0005 “Complex interdisciplinary studies of oceanological processes that determine functioning and evolution of the ecosystems of coastal zones of the Black and Azov seas”, as well as with support of the RFFI project No. 21-55-52001.

Original russian text

Original Russian Text © S. I. Kondratev, A. V. Varenik, N. A. Orekhova, 2023, published in MORSKOY GIDROFIZICHESKIY ZHURNAL, Vol. 39, Iss. 2, pp. 205-219 (2023)

For citation

Kondratev, S.I., Varenik, A.V. and Orekhova, N.A., 2023. Inorganic Forms of Nitrogen in the Deep Part of the Black Sea Based on the Expeditionary Data, 2016–2019. Physical Oceanography, 30(2), pp. 186-201. doi:10.29039/1573-160X-2023-2-186-201

DOI

10.29039/1573-160X-2023-2-186-201

References

  1. Wang, Q.S., Sun, D.-B., Hao, W.-P., Li, Y.-Z., Mei, X-R. and Zhang, Y.-Q., 2012. Human Activities and Nitrogen in Waters. Acta Ecologica Sinica, 32(4), pp. 174-179. doi:10.1016/j.chnaes.2012.04.010
  2. Kumar, P., Lai, S.H., Wong, J.K., Mohd, N.S., Kamal, M.R., Afan, H.A., Ahmed, A.N., Sherif, M., Sefelnasr, A. [et al.], 2020. Review of Nitrogen Compounds Prediction in Water Bodies Using Artificial Neural Networks and Other Models. Sustainability, 12(11), 4359. doi:10.3390/su12114359
  3. Gray, J.S., Wu, R.S-s. and Or, Y.Y., 2002. Effects of Hypoxia and Organic Enrichment on the Coastal Marine Environment. Marine Ecology Progress Series, 238, pp. 249-279. doi:10.3354/meps238249
  4. Rabalais, N.N., Diaz, R.J., Levin, L.A., Turner, R.E., Gilbert, D. and Zhang J., 2010. Dynamics and Distribution of Natural and Human-Caused Hypoxia. Biogeosciences, 7, pp. 585-619. doi:10.5194/bg-7-585-2010
  5. Glibert, P.M., 2017. Eutrophication, Harmful Algae and Biodiversity − Challenging Paradigms in a World of Complex Nutrient Changes. Marine Pollution Bulletin, 124(2), pp. 591-606. doi:10.1016/j.marpolbul.2017.04.027
  6. Cociasu, A., Dorogan, L., Humborg, C. and Popa, L., 1996. Long-Term Ecological Changes in Romanian Coastal Waters of the Black Sea. Marine Pollution Bulletin, 32(1), pp. 32-38. doi:10.1016/0025-326X(95)00106-W
  7. Friedrich, J., Dinkel, C., Friedl, G., Pimenov, N., Wijsman, J., Gomoiu, M.-T., Cociasu, A., Popa, L. and Wehrli, B., 2002. Benthic Nutrient Cycling and Diagenetic Pathways in the North-Western Black Sea. Estuarine, Coastal and Shelf Science, 54(3), pp. 369-383. doi:10.1006/ecss.2000.0653
  8. Sapozhnikov, V.V., 2006. [The Main Causes of Changes in the Ecosystems of the Black, Caspian and Azov Seas and Their Current State]. Voprosy Promyslovoj Okeanologii, 3, pp. 113-120. Available at: https://inlnk.ru/za2mnw [Accessed: 20 February 2023] (in Russian).
  9. Strokal, M. and Kroeze, C., 2013. Nitrogen and Phosphorus Inputs to the Black Sea in 1970– 2050. Regional Environmental Change, 13, pp. 179-192. doi:10.1007/s10113-012-0328-z
  10. Yunev, O.A., 2020. Second-Phase Eutrophication of the Black Sea Shelf. Ecological Safety of Coastal and Shelf Zones of Sea, (2), pp. 80-91. doi:10.22449/2413-5577-2020-2-80-91 (in Russian).
  11. Westley, M.B., Yamagishi, H., Popp, B.N. and Yoshida, N., 2006. Nitrous Oxide Cycling in the Black Sea Inferred from Stable Isotope and Isotopomer Distributions. Deep Sea Research Part II: Topical Studies in Oceanography, 53(17-19), pp. 1802-1816. doi:10.1016/j.dsr2.2006.03.012
  12. Kirkpatrick, J.B., Fuchsman, C.A., Yakushev, E., Staley, J.T. and Murray, J.W., 2012. Concurrent Activity of Anammox and Denitrifying Bacteria in the Black Sea. Frontiers in Microbiology, 3, 256. doi:10.3389/fmicb.2012.00256
  13. Solórzano, L., 1969. Determination of Ammonia in Natural Waters by the Phenolhypochlorite Method. Limnology and Oceanography, 14(5), pp. 799-801. doi:10.4319/lo.1969.14.5.0799
  14. Ivanov, V.A. and Belokopytov, V.N., 2013. Oceanography of the Black Sea. Sevastopol: ECOSY-Gidrofizika, 210 p.
  15. Konovalov, S.K. and Murray, J.W., 2001. Variations in the Chemistry of the Black Sea on a Time Scale of Decades (1960–1995). Journal of Marine Systems, 31(1-3), pp. 217-243. doi:10.1016/S0924-7963(01)00054-9
  16. Murray, J.W., 2005. Special Issue on Black Sea Oceanography. Oceanography, 18(2), pp. 14- 15. doi:10.5670/oceanog.2005.37
  17. Staneva, J., Kourafalou, V. and Tsiaras, K., 2010. Seasonal and Interannual Variability of the North-Western Black Sea Ecosystem. Terrestrial, Atmospheric and Oceanic Sciences, 21, pp. 163-180. doi:10.3319/TAO.2009.06.08.03(IWNOP)
  18. Chelysheva, M.V., Yakushev, E.V., Vinogradova, E.L. and Chasovnikov, V.K., 2012. Biogeochemical Peculiarities of the Vertical Distributions of Nutrients in the Black Sea. In: E. Yakushev, ed., 2011. Chemical Structure of Pelagic Redox Interfaces. Berlin, Heidelberg: Springer, pp. 13-26. doi:10.1007/698_2011_119
  19. Mikaelyan, A.S., Zatsepin, A.G. and Chasovnikov, V.K., 2013. Long-Term Changes in Nutrient Supply of Phytoplankton Growth in the Black Sea. Journal of Marine Systems, 117- 118, pp. 53-64. doi:10.1016/j.jmarsys.2013.02.012
  20. Tuğrul, S., Murray, J.W., Friederich, G.E. and Salihoğlu, I., 2014. Spatial and Temporal Variability in the Chemical Properties of the Oxic and Suboxic Layers of the Black Sea. Journal of Marine Systems, 135, pp. 29-43. doi:10.1016/j.jmarsys.2013.09.008
  21. Kirkpatrick, J.B., Fuchsman, C.A., Yakushev, E.V., Egorov, A.V., Staley, J.T. and Murray, J.W., 2018. Dark N2 Fixation: nifH Expression in the Redoxcline of the Black Sea. Aquatic Microbial Ecology, 82, pp. 43-58. doi:10.3354/ame01882
  22. Konovalov, S.K. and Eremeev, V.N., 2012. [Regional Features, Stability and Evolution of the Biogeochemical Structure of the Black Sea Waters]. In: S. K. Konovalov and N. Eremeev, eds., 2012. Stability and Evolution of Oceanological Characteristics of the Black Sea Ecosystem. Sevastopol: ECOSY-Gidrofizika, pp. 273-299 (in Russian).
  23. Masevich, A.V. and Konovalov, S.K., 2022. Oxygen Dynamics during the Period of Dystrophic Processes in the Black Sea. Physical Oceanography, 29(1), pp. 83-97. doi:10.22449/1573-160X-2022-1-83-97
  24. Fuchsman, C.A., Murray, J.W. and Konovalov, S.K., 2008. Concentration and Natural Stable Isotope Profiles of Nitrogen Species in the Black Sea. Marine Chemistry, 111(1-2), pp. 90- 105. doi:10.1016/j.marchem.2008.04.009
  25. Voss, M., Baker, A., Bange, H.W., Conley, D., Cornell, S., Deutsch, B., Engel, A., Ganeshram, R., Garnier, J. [et al.], 2011. Nitrogen Processes in Coastal and Marine Ecosystems. In: M. A. Sutton, C. M. Howard, J. W. Erisman, G. Billen, A. Bleeker, P. Grennfelt, H. van Grinsven, B. Grizzetti, eds., 2011. The European Nitrogen Assessment: Sources, Effects and Policy Perspectives. Cambridge: Cambridge University Press, pp. 147- 176. doi:10.1017/CBO9780511976988.011
  26. Konovalov, S.K., Fuchsman, C.A., Belokopitov, V. and Murray, J.W., 2008. Modeling the Distribution of Nitrogen Species and Isotopes in the Water Column of the Black Sea. Marine Chemistry, 111(1-2), pp. 106-124. doi:10.1016/j.marchem.2008.01.006
  27. Millero, F.J., 2005. Chemical Oceanography. 3rd Edition. Boca Raton: CRC Press, 536 p. doi:10.1201/9780429258718
  28. Silkin, V.A., Pautova, L.A., Pakhomova, S.V., Lifanchuk, A.V., Yakushev, E.V. and Chasovnikov, V.K., 2014. Environmental Control on Phytoplankton Community Structure in the NE Black Sea. Journal of Experimental Marine Biology and Ecology, 461, pp. 267-274. doi:10.1016/j.jembe.2014.08.009
  29. Konovalov, S.K., Murray, J.W., Luther, G.W. and Tebo, B.M., 2006. Processes Controlling the Redox Budget for the Oxic/Anoxic Water Column of the Black Sea. Deep-Sea Research II: Topical Studies in Oceanography, 53(17-19), pp. 1817-1841. doi:10.1016/j.dsr2.2006.03.013
  30. Konovalov, S.K., Ivanov, L.I. and Samodurov, A.S., 2001. Fluxes and Budget of Sulphide and Ammonia in the Black Sea Anoxic Layer. Journal of Marine Systems, 31(1-3), pp. 203- 216. doi:10.1016/S0924-7963(01)00053-7

Download the article (PDF)