Dimethylated sulfur compounds in seawater, seston and mesozooplankton in the seas around Turkey

Abstract

The spatial distribution of dimethylated sulfur compounds among particulate, dissolved matter and mesozooplankton in the Black, Marmara, Aegean and NE Mediterranean Seas were studied during October 2000. The surface concentration of particulate dimethylsulfoniopropionate (DMSP p) ranged from 5.4 (NE Mediterranean Sea) to 51.3 nM (Marmara Sea), and dimethylsulfoxide (DMSO p) from 0.8 (NE Mediterranean Sea) to 6.2 nM (Marmara Sea). Total particulate DMSP and DMSO concentrations from the depth of fluorescence maximum were comparable to or lower than those at the surface. Most of the particulate DMSP and DMSO were associated with particles <18 μm. The dissolved dimethylsulfide (DMS)+DMSP d pool in surface waters varied from a minimum of 5 nM in the NE Mediterranean Sea to a maximum of 17 nM in the Marmara Sea. Values of DMS:chlorophyll a (Chl- a), DMSP p:Chl- a and DMSO p:Chl- a ratios were lower in productive surface waters of the Black Sea and the Marmara Sea than in the oligotrophic waters of the Aegean and NE Mediterranean. None of the dimethylated sulfur compounds correlated significantly with Chl- a in the Black Sea. On the other hand, significantly negative correlation between Chl- a and DMSP p was found in surface waters of Aegean and NE Mediterranean Seas (data from the two seas were combined). We also found no significant correlations between the distribution of any particulate or dissolved dimethylated sulfur compounds and the abundance of mesozooplankton. Mesozooplankton constituted only ⩽5% of the total particulate DMSP in the water column. A preliminary estimate for average flux of dimethyl sulfide from the NE Mediterranean basin (including the Black Sea) to the atmosphere is 17.6 μmol m −2 d −1, indicating the potential importance of NE Mediterranean basin as a source of biogenic sulfur to the atmosphere, even in the less productive period.