Biological Production and Sea-Air Exchange of DMS in the Southern Ocean during the ACE-1 Experiment

Mark A.J.Curran, and Graham B.Jones (email:
Marine Chemistry Group
School of Molecular Sciences
James Cook University of North Queensland
Townsville, Queensland 4811 Australia.

F. Brian Griffiths, John S. Parslow and Lesley A. Clementson
CSIRO Division of Marine Research
GPO Box 1538
Hobart, Tasmania , Australia 7001

Measurements have been made of dimethylsulphide (DMS), and dimethylsulphoniopropionate (DMSP) in the Southern Ocean (40S, 140E; 54S, 153E) during the Southern Hemisphere Marine Aerosol Characterisation Experiment (ACE-1) from 17th November to 6th December 1995. The major findings from the study so far were the high levels of DMS and DMSP, associated with increased fluorescence and warmer sea surface temperatures between 45S, 143E and 46 40'S, 150E. Measurements of DMS and DMSP in surface waters during the Lagrangian "A" experiment together with process studies at fixed stations, suggest a diel pattern in particulate DMSP (DMSPp) concentration, with highest values usually found in the upper 25m at 22:00 hr. DMSPp and ammonium levels were positively correlated (r2 = 0.73) along the Lagrangian transect (46 33'S, 148E to 46 52'S, 152E), with highest levels of both NH4 and DMSPp in the warmer, Subtropical Convergence Zone water mass at the western end of the transect. In contrast, a highly significant negative correlation occurred between ammonium and dissolved DMSP (r2 = -0.86) along the Lagrangian A transect. These results will be integrated with dissolved nutrient, phytoplankton species and pigments, microzooplankton grazing rates, and primary production data to fully understand the links between the biology and the chemistry of the sulfur cycle in this region of the Southern Ocean. The ACE-1 DMS results, have been combined with seasonal DMS measurements made over a large area of the Southern Ocean (40S-70S; 100E-165E) from 1994-95, in order to obtain a more accurate estimate of DMS flux in this region. Extrapolating the DMS flux results from these studies, to the entire Southern Ocean, suggests that the emission of DMS is 28% of the total annual global emission of DMS, from 20% of the total ocean area.