AME 19:307-312 (1999)  -  doi:10.3354/ame019307

ABSTRACT: We measured the production of dimethylsulfide (DMS) by size-fractionated particles during a cruise in the Labrador Sea in May-June 1997. The experiments were conducted at 2 stations characterised by low levels of nitrate and high levels of phytoplankton biomass and particulate dimethylsulfoniopropionate (DMSP _p). Samples were size fractionated to assess the size distribution of DMSP _p and the potential DMS production associated with the different size fractions. The potential for DMS production was estimated by incubating the filters in pre-filtered and boiled seawater amended with 500 nM of dissolved DMSP (DMSP_d). At both stations, the highest DMSP _p concentrations were measured in the 2 to 11 and >20 μm size fractions. Elevated potential net DMS production rates were also associated with these 2 size fractions, which were responsible for 40 to 53% and 23 to 31% of the cumulative production, respectively. Only 4% of the potential net DMS production was measured in the 0.7 to 2 μm fraction, which presumably contained many of the free-living bacteria. The potential net DMS production rates of the different size fractions were linearly related (Spearman correlation coefficient = 0.86) to the concentrations of DMSP _p in the fractions. These results suggest that DMSP-cleaving activity was spatially associated with DMSP-producing algae or DMSP-rich detritus (e.g. faecal pellets, marine snow).

KEY WORDS: Dimethylsulfide (DMS) · Dimethylsulfoniopropionate (DMSP) · Bacteria · Phytoplankton · Labrador Sea · Size fraction