Physical Oceanography, Vol. 18, No. 2, 2008 EXPERIMENTAL AND FIELD RESEARCH ANALYSIS OF STATE OF THE CARBONATE SYSTEM OF WATERS AND VARIATIONS OF THE CONTENT OF ORGANIC CARBON IN BOTTOM SEDIMENTS OF THE SEVASTOPOL BAY IN 1998–2005 O. G. Ignat’eva, E. I. Ovsyanyi, A. S. Romanov, S. K. Konovalov, and N. A. Orekhova UDC 551.464.34 On the basis of the experimental data accumulated in 1998–2005, we analyzed the space and time variations of the carbonate system of waters and the content of organic carbon in bottom se- diments of the Sevastopol Bay. The intensity of gas exchange through the water–atmosphere in- terface was quantitatively estimated. It was shown that the partial pressure of carbon dioxide p CO 2 in waters of the bay became much higher for the period of observations. The maximum changes were observed in summer. They were especially pronounced for the bottom layer of wa- ters. For the entire period of observations, the invasion of carbon dioxide CO 2 was predominant in the major part of the bay, and the content of organic carbon in the bottom sediments increased. The ability of waters in the bay to absorb CO 2 is explained by the synthesis of organic sub- stances, which becomes possible due to the presence of the equivalent load of nutrients. Introduction For the last two centuries, the economic activity of the mankind was mainly based on the extensive utilization of natural resources. As a result, the existing balance between correlated natural processes was violated. Thus, for the last 200 yr, the concentration of CO 2 in the atmosphere became higher (as compared with the preindustrial level) by 30%. As a result, its partial pressure increased from 280 to 370 μ atm [1]. For the open part of the oceans, the elevation of the concentration of atmospheric carbon dioxide resulted in minor changes in the state of the carbonate system. At the same time, a decrease in the pH values and a significant growth of the amount of dissolved carbon dioxide were detected for the coastal regions and in waters of high latitudes [2–6]. Numerous researchers believe that, as a result of these processes, the ocean will lose its ability to absorb CO 2 from the atmosphere and may even turn into a source of CO 2 for the atmosphere. At the same time, as indicated in [7], the inflow of phosphorus into the ocean is now four times higher than in the preindustrial period and the nitrogen load has doubled for the same period. In [8, 9], it is shown that the inflow of phosphorus into the ocean is about twice higher than in the preindustrial period. Thus, it was assumed that the biological productivity of seas and oceans significantly increased. This, in turn, should lead to changes in the natural dynamic balance of CO 2 in the ocean–atmosphere system. At present, the state and the variability of the carbonate system, the directions and intensity of the fluxes of carbon dioxide, and the accumulation of organic carbon, i.e., the processes of high significance for the investiga- Marine Hydrophysical Institute, Ukrainian Academy of Sciences, Sevastopol, Ukraine. Translated from Morskoi Gidrofizicheskii Zhurnal, No. 2, pp. 57–67, March–April, 2008. Original article submitted May 22, 2006; revision submitted October 20, 2006. 96 0928-5105/08/1802–0096 © 2008 Springer Science+Business Media, Inc.