Particulate Dimethylsulfoniopropionate Removal and Dimethylsulfide Production by Zooplankton in the Southern Ocean

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Book Chapter

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Southern Ocean, Particulate Organic Carbon, Antarctic Peninsula, Dimethyl Sulfide, Drake Passage

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The influence of Antarctic krill, Euphausia superba, on particulate dimethlysulfoniopropionate (DMSP(p)) and dimethylsulfide (DMS) concentrations in surface waters of the Southern Ocean was investigated by shipboard experiments during austral spring near the Antarctic Peninsula. Chlorophyll concentrations were low in the water column, but substantially higher in sea ice due to the high biomass of ice algae, predominantly pennate diatoms. A comparison of DMSP(p) concentrations and algal accessory pigments indicated that DMSP(p) was associated primarily with diatoms (fucoxanthin) and to a minor extent with Phaeocystis spp. (19’-hexanoyloxyfucoxanthin) in sea ice algae. Maximum DMSP(p) and fucoxanthin concentrations also occurred in the 100-200 μm size fraction. We interpret this to mean that high biomass of diatoms in sea ice contributes significantly to DMSP(p) pools in the Antarctic.

Juvenile krill were the dominant biomass component of the zooplankton community and were often observed grazing along the edge of ice floes. In experiments, krill grazing on phytoplankton or ice algae produced 3 to 16 times the amount of DMS, respectively, relative to that in control bottles without krill. On average, juvenile krill produced 0.64 nmol DMS krill-1 h-1. Control bottles containing autotrophic and microheterotrophic organisms released only 0.03 nmol DMS L-1 h-1 and the net change in DMS due to microbial processes was neglible. Hence, krill appear to be very efficent in converting DMSP(p) to DMS. Krill also egested 1.06 nmol DMS(p) (mg fecal pellet)-1 h-1. Results from sediment traps, however, indicate that little DMSP(p) flux to deep water occurred even though particle fluxes were dominated by fecal pellets. DMSP(p) in fecal pellets may rapidly degrade to DMSP(d) and diffuse from pellets into the surrounding water. Our study indicates that mesozooplankton grazing activity plays a significant role in the release of DMSP and DMS from phytoplankton and ice algae. Because krill feed on ice algae during seasons when phytoplankton production is low, DMS production from grazing occurs during all seasons in the Southern Ocean.

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Citation / Publisher Attribution

Particulate Dimethylsulfoniopropionate Removal and Dimethylsulfide Production by Zooplankton in the Southern Ocean, in R. P. Kiene, P. T. Visscher, M. D. Keller & G. O. Kirst (Eds.), Biological and Environmental Chemistry of DMSP and Related Sulfonium Compounds, Springer, p. 223-238