The Production and Fate of Volatile Organosulfur Compounds in Sulfidic and Ferruginous Sediment

Abstract

Volatile organic sulfur compounds (VOSCs) link the atmospheric, marine, and terrestrial sulfur cycles in marine and marginal marine environments. Despite the important role VOSCs play in global biogeochemical sulfur cycling, less is known about how the local geochemical conditions influence production and consumption of VOSCs. We present a study of dimethyl sulfide (DMS), methanethiol (MeSH), and dimethylsulfoniopropionate (DMSP) in sulfide-rich (sulfidic) and iron-rich (ferruginous) salt marsh sediment from north Norfolk, UK. Initial results illustrate the importance of minimizing time between sampling in remote field locations and laboratory analysis, due to rapid degradation of VOSCs. With rapid analysis of sediment from different depths, we observe high concentrations of DMS, MeSH, and DMSP, with concentrations in surface sediment an order of magnitude higher than those in previous studies of surface water. We measure systematic differences in the concentration and depth distribution of MeSH and DMS between sediment environments; DMS concentrations are higher in ferruginous sediment, and MeSH concentrations are higher in sulfidic sediment. With repeated measurements over a short time period, we show that the degradation patterns for DMS and MeSH are different in the ferruginous versus sulfidic sediment. We discuss potential biogeochemical interactions that could be driving the observed differences in VOSC dynamics in ferruginous and sulfidic sediment. Plain Language SummaryOceans and coastal wetlands are dynamic environments where the carbon, sulfur, and iron biogeochemical cycles are tightly coupled. One important process that occurs in these environments is the formation of organic sulfur gases, which are involved in cloud formation and acid rain. Organic sulfur gases can be formed through a number of biological and chemical pathways, but little is known about how environmental conditions influence the chemical and microbial reactions that form these gases. In this study, we investigate how different chemical environments in salt marsh sediment influence the formation and destruction of organic sulfur gases. Different organic sulfur gases are produced in iron-rich environments compared to those produced in sulfide-rich environments. Further, the two geochemical environments also showed different patterns in the breakdown of these gases. These results indicate that the geochemical conditions influence how organic sulfur gases form and how they are released to the atmosphere. These findings have the potential to help explain observed differences in the release of organic sulfur gases among modern-day environments, as well as how the release of organic sulfur gases may have changed throughout Earth history as environmental conditions evolved.

Metagenomic Insights Into the Cycling of Dimethylsulfoniopropionate and Related Molecules in the Eastern China Marginal Seas

“…The sediment samples (top 5 cm surface sediment, predicted to span zones with the highest DMSP concentration; Wilkening et al, 2019) used in this study were collected in the YS (at sites termed H12, HS5, H25) and the BS (B41, B45, B47, B50) by grab sampler (Cuong and Obbard, 2006) and in the Okinawa Trough hydrothermal field at sites TVG11-2, TVG5-3, and T1 from sediment and polymetallic sulfide (see Figure 2 and Table 1 for locations and details of the sampling stations). The reported maximal photic zone depth of YS is ∼30 m (Jin et al, 2013), FIGURE 2 | The Eastern Chinese marginal seas sampling stations.…”

“…The sediment sampling regime in this study combined 0-5 cm deep sediment, which likely spanned large gradients in DMSP and DMS (Wilkening et al, 2019;Williams et al, 2019), oxygen, and diverse microbes. For this study, we have to consider these together, thus, the DMSP plus DMS content and microbial community data will be an average not reflecting that in the different sediment zones.…”

“…For this study, we have to consider these together, thus, the DMSP plus DMS content and microbial community data will be an average not reflecting that in the different sediment zones. For example, the DMSP and DMS concentration is likely to be far higher in the top ∼1 cm than in the deeper anoxic zone (Wilkening et al, 2019;Williams et al, 2019), which will likely have a distinct microbial profile. Nevertheless, the data presented here are convincing that the tested sediments are centers of high microbial organosulfur cycling activity.…”

“…It is clear from Carrión et al (2019); Wilkening et al (2019), and Williams et al (2019) that coastal marine sediments may be important sites for organosulfur cycling. However, very few studies have examined the genetic potential of marine sediments for the cycling of DMSP and related molecules.…”

Dimethylsulfoniopropionate Biosynthetic Bacteria in the Subseafloor Sediments of the South China Sea

“…Dimethylsulfoniopropionate content in surface marine sediments can be up to three orders of magnitude higher than most seawater samples, but these levels are reported to decrease with sediment depth and oxygen availability (Zhuang et al, 2017;Wilkening et al, 2019;Williams et al, 2019). For instance, DMSP concentration in surface sediment from saltmarsh ponds reached 128 nmol g −1 and reduced to 3.9-9.8 nmol g −1 in anoxic sediments, which was much higher than that in the overlying seawater (0.01-0.07 nmol ml −1 ) (Williams et al, 2019).…”