Abstract
Abstract. The production of dimethyl sulfide (DMS) is poorly quantified in tropical reef environments but forms an essential process that couples marine and terrestrial sulfur cycles and affects climate. Here we quantified net aqueous DMS production and the concentration of its cellular precursor dimethylsulfoniopropionate (DMSP) in the sea anemone Aiptasia sp., a model organism to study coral-related processes. Bleached anemones did not show net DMS production whereas symbiotic anemones produced DMS concentrations (mean ± standard error) of 160.7 ± 44.22 nmol g−1 dry weight (DW) after 48 h incubation. Symbiotic and bleached individuals showed DMSP concentrations of 32.7 ± 6.00 and 0.6 ± 0.19 µmol g−1 DW, respectively. We applied these findings to a Monte Carlo simulation to demonstrate that net aqueous DMS production accounts for only 20 % of gross aqueous DMS production. Monte Carlo-based estimations of sea-to-air fluxes of gaseous DMS showed that reefs may release 0.1 to 26.3 µmol DMS m−2 coral surface area (CSA) d−1 into the atmosphere with 40 % probability for rates between 0.5 and 1.5 µmol m−2 CSA d−1. These predictions were in agreement with directly quantified fluxes in previous studies. Conversion to a flux normalised to sea surface area (SSA) (range 0.1 to 17.4, with the highest probability for 0.3 to 1.0 µmol DMS m−2 SSA d−1) suggests that coral reefs emit gaseous DMS at lower rates than the average global oceanic DMS flux of 4.6 µmol m−2 SSA d−1 (19.6 Tg sulfur per year). The large difference between simulated gross and quantified net aqueous DMS production in corals suggests that the current and future potential for its production in tropical reefs is critically governed by DMS consumption processes. Hence, more research is required to assess the sensitivity of DMS-consumption pathways to ongoing environmental change in order to address the impact of predicted degradation of coral reefs on DMS production in tropical coastal ecosystems and its impact on future atmospheric DMS concentrations and climate.
Highlights
The DMSP-catabolite dimethyl sulfide (DMS) is a biogenic volatile organic compound (BVOC) that provides the dominant natural source of marine sulfur to the atmosphere with a release of 19.6 Tg S per year (Land et al, 2014)
Symbionts were the main source of DMSP and our data for symbiotic and bleached anemones are in general agreement with the earlier findings (Table 3) (Van Alstyne et al, 2009; Yancey et al, 2010)
Using the more sensitive invial purging method compared to the headspace sampling performed by Van Alstyne et al (2009), bleached anemones kept in darkness for 2 months showed an average DMSP concentration of 0.6 ± 0.19 μmol g−1 dry weight (DW) (n = 6)
Summary
The DMSP (dimethylsulfoniopropionate)-catabolite DMS (dimethyl sulfide) is a biogenic volatile organic compound (BVOC) that provides the dominant natural source of marine sulfur to the atmosphere with a release of 19.6 Tg S per year (Land et al, 2014) This biogenic sulfur affects cloud formation and climate (Vallina and Simó, 2007) and represents the key link in marine and terrestrial sulfur biogeochemical cycling (Bates et al, 1992). These anemones can be grown under the presence and absence of their symbionts This offers a unique opportunity to start dissecting the complex interactions between the main DMSP producer (Symbiodinium sp.), its host (Aiptasia) and the associated microbial community that, taken together, make up the anemone holobiont that releases DMS into the environment. Since information on the sea-to-air flux of DMS and other BVOCs from tropical reefs is scarce (Exton et al, 2014), this study quantified for the first time net aqueous DMS production (net DMSaq production) in Aiptasia sp. and used this data together with information on measured DMSP concentration within anemone holobionts (DMSPH) to simulate anemone gross aqueous DMS production (gross DMSaq production) and coral-derived seato-air flux of gaseous DMS (net DMSg flux)
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