Possible impacts of zooplankton grazing on dimethylsulfide production in the Antarctic Ocean

• Published in: Canadian Journal of Fisheries and Aquatic Sciences
• Main Authors: Kasamatsu, Nobue, Kawaguchi, So, Watanabe, Shuichi, Odate, Tsuneo, Fukuchi, Mitsuo
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 2004
• Subjects: Aquatic Science; Ecology, Evolution, Behavior and Systematics; Antarctic; The Antarctic; Antarctic Ocean; Antarc*; Antarctic Krill; Euphausia superba
• Online Access: http://dx.doi.org/10.1139/f04-072; http://www.nrcresearchpress.com/doi/pdf/10.1139/f04-072

The role of zooplankton grazing on dimethylsulfide (DMS) and dissolved dimethylsulfoniopropionate (DMSP d ) production was investigated in the Antarctic Ocean in January and February 2002. Dominant herbivorous macrozooplankton of this region, the Antarctic krill Euphausia superba and the tunicate Salpa thompsoni, were used in shipboard incubation experiments. The concentration of DMSP d + DMS increased in the water during incubation with krill. The production rate was 2.96 ± 2.78 nmol DMSP d + DMS·krill –1 ·h –1 (mean ± SD). In addition, the DMSP d + DMS production rate was linearly related to the ingestion rate of krill (r 2 = 0.664, p ≤ 0.01). Addition of salps to natural surface water, however, did not change the DMSP d + DMS concentrations. During the experiments, both animals fed on phytoplankton cells. The fecal pellets of krill contained broken phytoplankton cells, whereas those of salps contained unbroken cells. These results suggest that sloppy feeding by krill is a more likely mechanism for producing DMS and DMSP d than the direct ingestion of phytoplankton cells by salps. The decrease of DMS concentrations in the upper 200 m of the water column from January to February may be explained, in part, by changes in the composition of the macrozooplankton community.