Coupled dynamics of dimethylsulfoniopropionate and dimethylsulfide cycling and the microbial food web in surface waters of the North Atlantic

Abstract

Oceanic dimethylsulfide (DMS), the main natural source of sulfur to the global atmosphere, is suggested to play a key role in the interaction between marine biota and climate. Its biochemical precursor is dimethylsulfoniopropionate (DMSP), a globally distributed, intracellular constituent in marine phytoplankton. During a multidisciplinary Lagrangian experiment in the subpolar North Atlantic, we determined the fluxes of DMSP and DMS through phytoplankton, microzooplankton, and bacterioplankton and compared them with concurrent carbon and sulfur fluxes through primary and secondary productions, grazing, and release and use of dissolved organic matter. We found that DMSP and derivatives contributed most (48-100%) of the sulfur fluxes and 5-15% of the carbon fluxes. Our findings highlight DMSP as a prominent player in pelagic biogeochemical pumps, especially as a major carrier in organic sulfur cycling. Also, our results illustrate the key role played by microzooplankton and heterotrophic bacteria (hence the microbial food web) in controlling the amount of phytoplanktonic DMSP that ultimately vents to the atmosphere in the form of DMS.

Structures of dimethylsulfoniopropionate‐dependent demethylase from the marine organism Pelagabacter ubique

“…It has been well established that the planarity of the peptide bond is due to electronic resonance. In fact, not only can the carbonyl oxygen become negatively charged, but the NAH protons of protein backbones (1) and hydroxyl group of Y206 (2). The electron density is identical to what is described in Figure 3.…”

“…1,2 Although DMSP is used primarily as an intracellular osmolyte by phytoplankton, the compound has also been recognized as an antioxidant and predator deterrent. 3,4 While some phytoplankton can convert DMSP to dimethyl sulfide (DMS), upon phytoplankton lysis a considerable amount of DMSP is released and rapidly metabolized by the marine microbial food web.…”

Transcriptomic analysis of a marine bacterial community enriched with dimethylsulfoniopropionate

“…Although sulfate is much more abundant than DMSP in seawater (mM concentrations instead of nM), there are energetic advantages to taking up S that is already reduced. Previous studies have shown that DMSP can satisfy almost all the microbial community sulfur demands (Kiene and Linn, 2000a;Simó et al, 2002; Transcriptomics of a marine DMSP-consuming community M Vila-Costa et al Zubkov et al, 2002), and is particularly important in oligotrophic environments during periods of high solar irradiation when it contributes more to S fluxes (Simó et al, 2009). Accordingly, DMSPassimilating cells can account for up to 60% of the community in the Sargasso Sea (Vila et al, 2004;Malmstrom et al, 2004a, b).…”

Dissolved organic matter (DOM) release by phytoplankton in the contemporary and future ocean

“…Representatives from most of the major phylogenetic groups of eukaryote phytoplankton are known to produce DMSP (Malin & Kirst, 1997). Simó et al (2002) found that DMSP synthesis was proportional to photosynthesis in the North Atlantic and that phytoplankton invested 7% of net primary production into DMSP production. Compiling data from a range of in situ experiments and culture work, Kiene et al (2000) concluded that DMSP forms <1 to 39% of the cell carbon quota of phytoplankton, with most values lying in the range of 1-5%.…”