Total organic carbon dynamics in the Aegean Sea

Abstract : During the Mater oceanographic cruise, seawater samples were collected during September 1997 in the northern and southern parts of Aegean Sea and analyzed for total organic carbon (TOC) by using a high temperature catalytic oxidation method. Our results indicate that TOC concentrations decreased from the surface to deep waters from 52-128 to 48-56 AM C in the North and from 55-87 to 47-56 AM C in the South. Standing stocks of TOC in the upper 100 m, ranged from 6300 to 9120 mmol C m -2 in the North and from 6563 to 7483 mmol C m -2 in the South. Basically, higher concentrations were observed in the North and particularly for waters where the signature of Black Sea water was more pronounced. From salinity-TOC relationships, we estimated that TOC input from the Marmara and Black Sea to the Mediterranean Sea through the Dardanelles Strait varied from 1.6 to 23.7 x 10 10 mol C year -1. Our computations of TOC budget suggest that TOC inflow through Dardanelles Strait, is slightly lower than TOC input from Mediterranean rivers and from the atmosphere, whereas it is one order of magnitude lower than that reported for the Atlantic Ocean via the Gibraltar Strait. We also discuss the distribution of TOC in relation to bacterial production (BP) and associated bacterial carbon demand (BCD). Assuming a bacterial growth efficiency (BGE) of 0.30, BCD in the upper 100 m was on average 18.1 mmol C m À2 day À1 in the North and 15.5 mmol C m À2 day À1 in the South. Turnover times of excess TOC (calculated as the difference between surface water TOC and a mean value of TOC below 200 m) in the upper 100 m were higher in the northern basin (0.28-0.59 years; av. 0.47 years) than in the central Aegean basin (0.20 years) and the southern basin (0.20-0.36 years; av. 0.28 years). These results may vary and need to be cautiously taken into account because of the uncertainties associated to the BGE. However, this study indicates that bacterial cycling of TOC is more effective in the South Aegean than in the North, which leads to a higher accumulation of TOC in North Aegean surface waters.
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Richard Sempere, C. Panagiotopoulos, R. Lafont, B Marroni, F. van Wambeke. Total organic carbon dynamics in the Aegean Sea. Journal of Marine Systems, Elsevier, 2001. ⟨hal-02065006⟩

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