Physical Oceanography, Vol.
2, July, 2011 (Ukrainian Original No.
2, March–April, 2011)
INVESTIGATION OF THE MECHANISM OF THE LONG-TERM EVOLUTION OF
THE CARBON CYCLE IN THE ECOSYSTEM OF THE SEVASTOPOL BAY
O. G. Moiseenko
and N. A. Orekhova
We analyze the components of the carbon system of the Sevastopol bay waters and the balance of main
sediment-forming substances using the data of field investigations in 1998–2008. The interannual varia-
tions of total inorganic carbon and the equilibrium partial pressure of carbon dioxide in the bay water are
noted. An increase in the flux of carbon dioxide
into the bay and in the content of organic carbon in bot-
tom sediments is revealed, and an explanation of this phenomenon is given. The priority accumulation
of organic carbon in the sediments of the bay is established. We assess the interannual variation in the
relative abundances of organic and inorganic carbon as an index of the carbon cycle stability.
Keywords: carbon cycle, components of the carbon system, Sevastopol bay.
Coastal water areas are the zones of interaction of land, sea, and atmosphere. This is exactly the place
where the main biogeochemical processes (the formation of primary production, respiration, transformation of
organic carbon into inorganic carbon, deposition and burial of carbon, and interaction and substance exchange
with the land and atmosphere) run most intensively.
The biogeochemical cycles of coastal ecosystems are subject, first of all, to increasing anthropogenic pres-
sure, especially due to the huge amount of organic carbon and nutrients coming from the land. As compared
with preindustrial times, the amount of nitrogen coming to the water as a result of human activity has increased
by a factor of five . It was shown in [2, 3] that the inflow of phosphorus to the ocean is approximately twice
as high as in preindustrial times. The increase in the concentration of carbon dioxide in atmosphere by more
than 20% for the last 200 years  caused a transformation of the carbon cycle in coastal water areas: in coastal
regions, a decrease in pH was recorded and a significant increase in the content of dissolved carbon dioxide was
observed [3, 5–8].
The Sevastopol bay, which was chosen as the object of investigation, is a notable example of a coastal water
area subject to permanently increasing anthropogenic pressure for the last two centuries. It is a semiclosed water
area of the estuary type. Its length from the entry to the tip is ~7 km, the maximum width is ~1 km, and the
mean depth is 12 m. The surface area of the bay is 7.96 km
. After the construction of a protective pier in
1977–1978, the entry width decreased from 940 to 550 m, which caused significant changes in the characteris-
tics of water exchange. On the average per year, it decreased by 40–70%, and the duration of the “full” water
exchange in the bay increased almost twice .
The state of the carbon cycle and its components in the Sevastopol bay was studied earlier in a number of
works [10–14], and the sinks and sources of carbon dioxide in the bay were discussed in our works [15–17].
The purpose of the present work is to study the long-term dynamics of components of the carbon system of
waters and the contents of organic and inorganic carbon in the bottom sediments of the Sevastopol bay on the
basis of the data of investigations carried out in 1998–2008 and to estimate the possibility of using relative indi-
Marine Hydrophysical Institute of the Ukrainian Academy of Sciences, Sevastopol; e-mail: firstname.lastname@example.org.
Marine Hydrophysical Institute of the Ukrainian Academy of Sciences, Sevastopol; e-mail: email@example.com.
Translated from Morskoi Gidrofizicheskii Zhurnal, No.
72–83, March–April, 2011. Original article submitted January 25, 2010;
revision submitted March 4, 2010.
142 0928–5105/11/2102–0142 © 2011 Springer Science+Business Media, Inc.