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Ocean Science An interactive open-access journal of the European Geosciences Union
Ocean Sci., 13, 961-982, 2017
https://doi.org/10.5194/os-13-961-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
23 Nov 2017
Dimethylsulfoniopropionate (DMSP) and dimethyl sulfide (DMS) cycling across contrasting biological hotspots of the New Zealand subtropical front
Martine Lizotte1, Maurice Levasseur1, Cliff S. Law2,3, Carolyn F. Walker2, Karl A. Safi4, Andrew Marriner2, and Ronald P. Kiene5 1Université Laval, Department of biology (Québec-Océan), Québec City, Québec, Canada
2National Institute of Water and Atmospheric Research, Wellington, New Zealand
3University of Otago, Department of Chemistry, Dunedin, New Zealand
4National Institute of Water and Atmospheric Research, Hamilton, New Zealand
5University of South Alabama, Department of Marine Sciences, Mobile, AL, USA
Abstract. The oceanic frontal region above the Chatham Rise east of New Zealand was investigated during the late austral summer season in February and March 2012. Despite its potential importance as a source of marine-originating and climate-relevant compounds, such as dimethyl sulfide (DMS) and its algal precursor dimethylsulfoniopropionate (DMSP), little is known of the processes fuelling the reservoirs of these sulfur (S) compounds in the water masses bordering the subtropical front (STF). This study focused on two opposing short-term fates of DMSP-S following its uptake by microbial organisms (either its conversion into DMS or its assimilation into bacterial biomass) and has not considered dissolved non-volatile degradation products. Sampling took place in three phytoplankton blooms (B1, B2, and B3) with B1 and B3 occurring in relatively nitrate-rich, dinoflagellate-dominated subantarctic waters, and B2 occurring in nitrate-poor subtropical waters dominated by coccolithophores. Concentrations of total DMSP (DMSPt) and DMS were high across the region, up to 160 and 14.5 nmol L−1, respectively. Pools of DMSPt showed a strong association with overall phytoplankton biomass proxied by chlorophyll a (rs  =  0.83) likely because of the persistent dominance of dinoflagellates and coccolithophores, both DMSP-rich taxa. Heterotrophic microbes displayed low S assimilation from DMSP (less than 5 %) likely because their S requirements were fulfilled by high DMSP availability. Rates of bacterial protein synthesis were significantly correlated with concentrations of dissolved DMSP (DMSPd, rs  =  0.86) as well as with the microbial conversion efficiency of DMSPd into DMS (DMS yield, rs  =  0.84). Estimates of the potential contribution of microbially mediated rates of DMS production (0.1–27 nmol L−1 day−1) to the near-surface concentrations of DMS suggest that bacteria alone could not have sustained DMS pools at most stations, indicating an important role for phytoplankton-mediated DMS production. The findings from this study provide crucial information on the distribution and cycling of DMS and DMSP in a critically under-sampled area of the global ocean, and they highlight the importance of oceanic fronts as hotspots of the production of marine biogenic S compounds.

Citation: Lizotte, M., Levasseur, M., Law, C. S., Walker, C. F., Safi, K. A., Marriner, A., and Kiene, R. P.: Dimethylsulfoniopropionate (DMSP) and dimethyl sulfide (DMS) cycling across contrasting biological hotspots of the New Zealand subtropical front, Ocean Sci., 13, 961-982, https://doi.org/10.5194/os-13-961-2017, 2017.
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Short summary
During a 4-week oceanographic cruise in 2012, we investigated the water masses bordering the subtropical front near New Zealand as sources of the biogenic gas dimethyl sulfide (DMS). DMS oxidation products may influence the atmospheric radiative budget of the Earth. Concentrations of DMS were high in the study region and DMS's precursor, dimethylsulfoniopropionate, showed a strong association with phytoplankton biomass in relation to the persistent dominance of dinoflagellates/coccolithophores.
During a 4-week oceanographic cruise in 2012, we investigated the water masses bordering the...
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