MEPS 295:33-42 (2005)  -  doi:10.3354/meps295033

Gradients in dimethylsulfide, dimethylsulfoniopropionate, dimethylsulfoxide, and bacteria near the sea surface

Hendrik J. Zemmelink1,2,* , Leah Houghton1, Stefan M. Sievert1, Nelson M. Frew1, John W. H. Dacey1

1Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543, USA
2Present address: School of Environmental Sciences, University of East Anglia, Norwich NR4 7TJ, UK

ABSTRACT: Gradients of dimethylsulfide (DMS), dimethylsulfoniopropionate (DMSP), dimethylsulfoxide (DMSO), and bacterial numbers and diversity from the surface microlayer to 500 cm depth were assessed in coastal waters surrounding the Martha’s Vineyard Coastal Observatory, Massachusetts, USA. Microlayer samples were collected with a surface skimmer: a partially submerged, rotating glass cylinder (‘drum’) that allows the collection of a thin layer of water by adherence to the drum. A depletion of DMS towards the water surface (10 cm) was found at all sampling days, with largest gradients during rough sea surface conditions. The steep gradients show that gas fluxes and transfer velocities, based on the concentration disequilibrium between the water and the atmosphere, need to be based on near surface gas concentration values. Elevated DMSP, DMSO concentrations and bacterial numbers were found at the sea surface during calm conditions. Although degassing and photo-oxidation on the skimmer will bias the microlayer data, the results indicate stratification of DMSP, DMSO and bacteria during periods of smooth sea surface conditions.

KEY WORDS: Marine sulfur · Bacteria · Depth profiles · Microlayer sampling · Coastal waters · DMS · DMSP · DMSO

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