Sea Ice and Water Mass Influence Dimethylsulfide Concentrations in the Central Arctic Ocean

Christiane Uhlig,Benjamin Rabe,Ilka Peeken,Meri Korhonen,Thomas Krumpen,Kai-Uwe Ludwichowski,Ellen Damm

doi:10.3389/feart.2019.00179

Abstract

Dimethylsulfide (DMS) is a biogenic trace gas with importance to aerosol formation. DMS is produced by microbial degradation of dimethylsulfoniopropionate (DMSP), an abundant metabolite in marine microalgae. We analyzed DMS and DMSP concentrations in surface water in the central Arctic Ocean during two expeditions north of 79°N in 2011 and 2015. We identified three regions, which were characterized by different DMS and DMSP concentrations, dependent on the regional water masses and the relative movement of sea ice and water to each other. In addition, correlations between DMS and DMSP and correlation of the two sulfur compounds to autotrophic biomass (as chlorophyll a) differed in the regions. In the area of the nutrient rich Atlantic water inflow and short contact of this water with sea ice, DMS is present in high concentrations and correlates to DMSP as well as chlorophyll a. At two stations, particularly high DMS concentrations were found in conjunction with under-ice phytoplankton biomass peaks. In contrast, in mixed Atlantic and Pacific water with strong polar influence, where long-term contact between sea ice and water causes persistent stratification, only little DMS is found. Further, the correlations to DMSP and chlorophyll a are lost and the ratio of DMS to DMSP is about one order of magnitude lower, pointing towards consumption of DMSP without the production of DMS. We conclude that the duration of sea ice influence and source of the surface water do not only lead to differences in phytoplankton productivity, resulting in different DMSP concentrations, but also influence microbial recycling of DMSP to DMS or other compounds. DMS production, as possible source for aerosols, is thus presumably lower in the strongly sea ice influenced central Arctic areas than what could be expected from DMSP concentration or biomass.

Highlights

Dimethylsulfide (DMS) represents the most important natural source of sulfur to the atmosphere, accounting for up to 80% of global biogenic sulfur emissions (Keller et al, 1989; Liss et al, 1997; Kettle and Andreae, 2000)
Our study shows strong heterogeneity of DMS and DMSP concentrations in ice covered surface waters between different regions of the central Arctic
Little DMS and DMSP are found in the eastern Eurasian Basin (Region 2) and the region influenced by Pacific waters (Region 3)

Summary

Introduction

Dimethylsulfide (DMS) represents the most important natural source of sulfur to the atmosphere, accounting for up to 80% of global biogenic sulfur emissions (Keller et al, 1989; Liss et al, 1997; Kettle and Andreae, 2000). In the Arctic, several studies show a coincidence or strong contribution of DMS to aerosol formation This is pronounced during phytoplankton blooms (Park et al, 2017) and in the summer, when other condensation nuclei, e.g., from anthropogenic sources or sea salts, are low (Chang et al, 2011; Leaitch et al, 2013; Ghahremaninezhad et al, 2016). Bacteria either lyse DMSP to assimilate the carbon and produce DMS as side product, or demethylate DMSP to assimilate both carbon and sulfur. The balance between both pathways is controlled by the sulfur demand of the bacterial community. Major removal processes of DMS from seawater are bacterial uptake and degradation, photo-oxidation and sea-air flux (Kiene and Bates, 1990; Simó, 2004; del Valle et al, 2009)

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