Dimethylsulfoniopropionate Research Articles

Phytoplankton-derived zwitterionic gonyol and dimethylsulfonioacetate interfere with microbial dimethylsulfoniopropionate sulfur cycling.

The marine sulfur cycle is substantially fueled by the phytoplankton osmolyte dimethylsulfoniopropionate (DMSP). This metabolite can be metabolized by bacteria, which results in the emission of the volatile sulfur species methanethiol (MeSH) and the climate‐cooling dimethylsulfide (DMS). It is generally accepted that bacteria contribute significantly to DMSP turnover. We show that the other low molecular weight zwitterionic dimethylsulfonio compounds dimethylsulfonioacetate (DMSA) and gonyol are also widely distributed in phytoplankton and can serve as alternative substrates for volatile production. DMSA was found in 11 of the 16 surveyed phytoplankton species, and gonyol was detected in all haptophytes and dinoflagellates. These prevalent zwitterions are also metabolized by marine bacteria. The patterns of bacterial MeSH and DMS release were dependent on the zwitterions present. Certain bacteria metabolize DMSA and gonyol and release MeSH, in others gonyol inhibited DMS‐producing enzymes. If added in addition to DMSP, gonyol entirely inhibited the formation of volatiles in Ruegeria pomeroyi. In contrast, no substantial effect of this compound was observed in the DMSP metabolism of Halomonas sp. We argue that the production of DMSA and gonyol and their inhibitory properties on the release of volatiles from DMSP has the potential to modulate planktonic sulfur cycling between species.

Seasonal Changes in Microbial Dissolved Organic Sulfur Transformations in Coastal Waters.

The marine trace gas dimethylsulfide (DMS) is the single most important biogenic source of atmospheric sulfur, accounting for up to 80% of global biogenic sulfur emissions. Approximately 300 million tons of DMS are produced annually, but the majority is degraded by microbes in seawater. The DMS precursor dimethylsulfoniopropionate (DMSP) and oxidation product dimethylsulphoxide (DMSO) are also important organic sulfur reservoirs. However, the marine sinks of dissolved DMSO remain unknown. We used a novel combination of stable and radiotracers to determine seasonal changes in multiple dissolved organic sulfur transformation rates to ascertain whether microbial uptake of dissolved DMSO was a significant loss pathway. Surface concentrations of DMS ranged from 0.5 to 17.0 nM with biological consumption rates between 2.4 and 40.8 nM·d−1. DMS produced from the reduction of DMSO was not a significant process. Surface concentrations of total DMSO ranged from 2.3 to 102 nM with biological consumption of dissolved DMSO between 2.9 and 111 nM·d−1. Comparisons between 14C2-DMSO assimilation and dissimilation rates suggest that the majority of dissolved DMSO was respired (>94%). Radiotracer microbial consumption rates suggest that dissimilation of dissolved DMSO to CO2 can be a significant loss pathway in coastal waters, illustrating the significance of bacteria in controlling organic sulfur seawater concentrations.

Chemical Diversity and Biochemical Transformation of Biogenic Organic Sulfur in the Ocean

Organic sulfur compounds are not only essential for organismal survival but also indispensable for the sulfur cycle. Over the past few decades, dimethylsulfoniopropionate (DMSP) and dimethyl sulfide (DMS) cycling in the upper ocean have been well characterized from the genetic to the ecosystem level. Recent advances in the study of marine sulfonate transformation have indicated that phytoplankton and microbes play key roles in oceanic sulfur and carbon fluxes. This review provides biochemical details of the major sulfur metabolites, and presents an interlinked reaction network with genetic information on the microbial transformation and mineralization of sulfur compounds. This review also discusses future prospects for the discovery and characterization of novel substrates and enzymes involved in organosulfur cycling, as well as for investigations of deep sea and sedimentary organic sulfur.

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

The microbial cycling of dimethylsulfoniopropionate (DMSP) and its gaseous catabolites dimethylsulfide (DMS) and methanethiol (MeSH) are important processes in the global sulfur cycle, marine microbial food webs, signaling pathways, atmospheric chemistry, and potentially climate regulation. Many functional genes have been identified and used to study the genetic potential of microbes to produce and catabolize these organosulfur compounds in different marine environments. Here, we sampled seawater, marine sediment and hydrothermal sediment, and polymetallic sulfide in the eastern Chinese marginal seas and analyzed their microbial communities for the genetic potential to cycle DMSP, DMS, and MeSH using metagenomics. DMSP was abundant in all sediment samples, but was fivefold less prominent in those from hydrothermal samples. Indeed, Yellow Sea (YS) sediment samples had DMSP concentrations two orders of magnitude higher than in surface water samples. Bacterial genetic potential to synthesize DMSP (mainly in Rhodobacteraceae bacteria) was far higher than for phytoplankton in all samples, but particularly in the sediment where no algal DMSP synthesis genes were detected. Thus, we propose bacteria as important DMSP producers in these marine sediments. DMSP catabolic pathways mediated by the DMSP lyase DddP (prominent in Pseudomonas and Mesorhizobium bacteria) and DMSP demethylase DmdA enzymes (prominent in Rhodobacteraceae bacteria) and MddA-mediated MeSH S-methylation were very abundant in Bohai Sea and Yellow Sea sediments (BYSS) samples. In contrast, the genetic potential for DMSP degradation was very low in the hydrothermal sediment samples—dddP was the only catabolic gene detected and in only one sample. However, the potential for DMS production from MeSH (mddA) and DMS oxidation (dmoA and ddhA) was relatively abundant. This metagenomics study does not provide conclusive evidence for DMSP cycling; however, it does highlight the potential importance of bacteria in the synthesis and catabolism of DMSP and related compounds in diverse sediment environments.

Combined effects of elevated temperature and pCO2 on the production of DMSP and DMS in the culture of Amphidinium carterae

Ocean acidification and global warming might affect the production of dimethylsulfoniopropionate (DMSP), dimethylsulfide (DMS), and dissolved acrylic acid (AAd) by marine phytoplankton. Monoculture incubation experiments were conducted with the dinoflagellate Amphidinium carterae to investigate the effects of elevated CO2 concentration and temperature on growth and productions of DMSP, DMS, and AAd. Two pCO2 levels were set as 400 and 1000 μatm, and two temperatures were set as 20 and 23 °C. The growth of A. carterae remained unaffected by an increase of CO2 to 1000 μatm and a rise of temperature of 3 °C. Moreover, the elevated CO2 concentration and temperature had no significant effects on the concentrations and cell-normalized concentrations of DMSP, DMS, and AAd. No additive or synergistic effects of elevated CO2 concentration and temperature on A. carterae were observed, indicating that A. carterae was insensitive to elevated CO2 and temperature in short time incubation.

Comparative genomics: Dominant coral-bacterium Endozoicomonas acroporae metabolizes dimethylsulfoniopropionate (DMSP)

Dominant coral-associated Endozoicomonas bacteria species are hypothesized to play a role in the coral sulfur cycle by metabolizing dimethylsulfoniopropionate (DMSP) into dimethylsulfide (DMS); however, no sequenced genome to date harbors genes for this process. In this study, we assembled high-quality (>95% complete) draft genomes of strains of the recently added species Endozoicomonas acroporae (Acr-14T, Acr-1, and Acr-5) isolated from the coral Acropora sp. and performed a comparative genomic analysis on the genus Endozoicomonas. We identified DMSP CoA-transferase/lyase—a dddD gene homolog in all sequenced genomes of E. acroporae strains—and functionally characterized bacteria capable of metabolizing DMSP into DMS via the DddD cleavage pathway using RT-qPCR and gas chromatography (GC). Furthermore, we demonstrated that E. acroporae strains can use DMSP as a carbon source and have genes arranged in an operon-like manner to link DMSP metabolism to the central carbon cycle. This study confirms the role of Endozoicomonas in the coral sulfur cycle.

Insights on the genetic repertoire of the coral Mussismilia braziliensis endosymbiont Symbiodinium

Reef-building corals form a symbiotic association with photosynthetic dinoflagellates of the family Symbiodiniaceae. This symbiosis is crucial for the maintenance of coral reefs. In this work, we evaluate the effect of light conditions on the transcriptomic response of Symbiodinium CCMR0100 (ITS2 type A4), isolated from the Southwestern Atlantic Ocean endemic Mussismilia braziliensis. We obtained a total of 36,224 transcripts (N50 = 1007 bases, mean GC = 55.7%; ~25 Gb of assembled bases). We observed ecologically relevant transcripts encoding i. the complete antioxidant enzymatic system, ii. the recently described algal dimethylsulfoniopropionate (DMSP) lyase, and iii. The Mycosporine-like aminoacids (MAA) biosynthesis pathway. Cultures maintained in dark and light conditions yielded different transcriptomic profiles, and 48 transcripts were differentially expressed between these treatments. Expression of cytochrome P450 was inhibited by light, suggesting that endoplasmic reticulum monooxygenase activity might play a role in light-independent coral bleaching. Light conditions also triggered the induction of transcripts associated to chromatin condensation and mitosis, consistent with the light dependent progression of Symbiodiniaceae cell cycle. The repression of transcripts associated to the phosphatidylinositol (PI) signaling pathwaysuggests this pathway shall be related to light-induced morphological changes in Symbiodiniaceae cell.

Distribution Characteristics of Dimethylated Sulfur Compounds and Turnover of Dimethylsulfide in the Northern South China Sea During Summer

AbstractSpatial distributions of dimethylsulfide (DMS), dimethylsulfoniopropionate (DMSP), and dimethyl sulfoxide (DMSO) in the northern South China Sea were determined in the summer of 2015. The mean concentrations of DMS, particulate DMSP (DMSPp), dissolved DMSP (DMSPd), dissolved DMSO (DMSOd), and particulate DMSO (DMSOp) in the surface seawater were 2.8 ± 1.0, 6.8 ± 1.5, 14.0 ± 3.1, 12.2 ± 3.2, and 9.2 ± 2.6 nmol L−1, respectively. The contributions of three principal removal pathways of DMS were investigated. The average biological production and consumption rates of DMS in the surface seawater were 6.15 ± 1.12 and 4.63 ± 1.32 nmol L−1 day−1. Deck incubation experiments showed that the photooxidation rates of DMS for different radiation bands followed the order: KUVB > KUVA > Kvisible light. The DMS photooxidation rates were higher in the coastal waters than in the open ocean, which might be associated with the higher concentrations of dissolved organic matter of terrigenous input. The sea‐to‐air fluxes of DMS ranged from 1.6 to 50.3 μmol m−2 day−1 with an average value of 15.6 ± 11.6 μmol m−2 day−1. Based on the respective turnover times of DMS, the contributions of biological consumption, photooxidation, and sea‐to‐air exchange to the sink of DMS were 32.6 ± 11.0%, 23.2 ± 8.9%, and 44.1 ± 19.2%, respectively, suggesting that the three removal pathways were all critical to the migration and transformation of DMS in the surface seawater during summer.

A 15-Month Survey of Dimethylsulfoniopropionate and Dimethylsulfoxide Content in Posidonia oceanica

Posidonia oceanica is the only reported seagrass to produce significant amount of dimethylsulfoniopropionate (DMSP). It is also the largest known producer of DMSP among coastal and inter-tidal higher plants. Here we studied i) the weekly to seasonal variability and the depth variability of DMSP and its related compound dimethylsulfoxide (DMSO) in P. oceanica leaves of a non-disturbed meadow in Corsica, France, ii) the weekly to seasonal variability and the depth variability of DMSP to DMSO concentration to assess the potential of the DMSP:DMSO ratio as indicator of stress, and iii) the relationships between DMSP, DMSO and the DMSP:DMSO ratio with potential explanatory variables such as light, temperature, photosynthetic activity (effective quantum yield of photosystem II) and leaf size. The overall average concentrations of organosulfured compounds in P. oceanica leaves were 130 ± 39 μmol.gfw-1 for DMSP and 4.9 ± 2.1 μmol.gfw-1 for DMSO. Concentrations of DMSP and DMSO in P. oceanica leaves were overall distinctly higher and exhibited a wider range of variations than other marine primary producers. Concentrations decreased from a maximum in autumn to a minimum in summer; they changed little with depth. Potential explanatory variables except the leaf size, i.e., the leaf age were little or not related to measured concentrations. To explain the seasonal pattern of decreasing concentrations with leaf aging, we hypothesized two putative protection functions of DMSP in young leaves: antioxidant against reactive oxygen species and predator-deterrent. The similar variation of the two molecule concentrations over time and with depth suggested that DMSO content in P. oceanica leaves results from oxidation of DMSP. The DMSP:DMSO ratio remained constant around a mean value of 29.2 ± 9.0 µmol:µmol for the non-disturbed harvested meadow regardless of the time of the year, the depth or the leaf size. As suggested for the salt march plant S. alterniflora, we hypothesized the DMSP:DMSO ratio could be considered as indicator of stress in seagrasses exposed to environmental or anthropogenic stressors. More research would now be needed to confirm the functions of DMSP and DMSO in seagrasses and how the DMSP:DMSO ratio will vary under various disturbances.

Evidence for contrasting roles of dimethylsulfoniopropionate production in Emiliania huxleyi and Thalassiosira oceanica.

Summary Dimethylsulfoniopropionate (DMSP) is a globally abundant marine metabolite and a significant source of organic carbon and sulfur for marine microbial ecosystems with the potential to influence climate regulation. However, the physiological function of DMSP has remained enigmatic for >30 yr. Recent insight suggests that there are different physiological roles for DMSP based on the cellular DMSP concentrations in producers.Differential production of DMSP was tested with multiple physiological experiments that altered nitrate availability, salinity and temperature to create stressed growth and target different metabolic conditions in Emiliania huxleyi, a high DMSP producer and Thalassiosira oceanica, a low DMSP producer. Emiliania huxleyi intracellular DMSP did not respond to metabolically imbalanced conditions, while Thalassiosira oceanica intracellular DMSP was significantly correlated to stressed growth rate across all conditions tested and exhibited a plastic response on a timescale of hours in nonsteady‐state.The previous assumption that proposed DMSP mechanism(s) can be universally applied to all producers is shown to be unlikely. Rather, two distinct ecological roles for DMSP likely exist that differ by producer type, where: (1) the primary role of DMSP in high producers is a constitutive compatible solute; and (2) DMSP production in low producers is a finely tuned stress response.

Ectoine from Bacterial and Algal Origin Is a Compatible Solute in Microalgae.

Osmoregulation in phytoplankton is attributed to several highly polar low-molecular-weight metabolites. A widely accepted model considers dimethylsulfoniopropionate (DMSP) as the most important and abundant osmotically active metabolite. Using an optimized procedure for the extraction and detection of highly polar metabolites, we expand the group of phytoplankton osmolytes by identifying ectoine in several microalgae. Ectoine is known as a bacterial compatible solute, but, to the best of our knowledge, was never considered as a phytoplankton-derived product. Given the ability of microalgae to take up zwitterions, such as DMSP, we tested the hypothesis that the algal ectoine is derived from associated bacteria. We therefore analyzed methanol extracts of xenic and axenic cultures of two different species of microalgae and could detect elevated concentrations of ectoine in those that harbor associated bacteria. However, also microalgae without an associated microbiome contain ectoine in smaller amounts, pointing towards a dual origin of this metabolite in the algae from their own biosynthesis as well as from uptake. We also tested the role of ectoine in the osmoadaptation of microalgae. In the model diatoms Thalassiosira weissflogii and Phaeodactylum tricornutum, elevated amounts of ectoine were found when cultivated in seawater with salinities of 50 PSU compared to the standard culture conditions of 35 PSU. Therefore, we add ectoine to the family of osmoadaptive metabolites in phytoplankton and prove a new, potentially synergistic metabolic interplay of bacteria and algae.

Dimethylsulfoniopropionate (DMSP) and dimethylsulfoxide (DMSO) cell quotas variations arising from sea ice shifts of salinity and temperature in the Prymnesiophyceae Phaeocystis antarctica

Environmental contextDimethylsulfoniopropionate and dimethylsulfoxide could have a climatic influence especially in the polar areas. We investigate the effect of sea ice salinity and temperature on the production of these two sulfur metabolites by a polar microalga, and suggest their potential roles of osmoregulator and cryoprotectant. These results bring new information about the sulfur cycle in sea ice that is useful for climate models. AbstractThe Southern Ocean, which includes the seasonal ice zone (SIZ), is a source of large sea-air fluxes of dimethylsulfide (DMS), a climate active gas involved in Earth cooling processes. In this area, the prymnesiophyte Phaeocystis antarctica (P. antarctica) is one of the main producers of dimethylsulfoniopropionate (DMSP) and dimethylsulfoxide (DMSO), two metabolites that are precursors of DMS. These algae are also present in sea ice and contribute substantially to the high DMSP and DMSO concentrations observed in this habitat. DMSP and DMSO production in sea ice by P. antarctica is proposed to be promoted by its ability to live in extreme environmental conditions. We designed cell culture experiments to test that hypothesis, focusing on the impact of shifts of temperature and salinity on the DMSP and DMSO cell quotas. Our experiments show an increase in DMSP and DMSO cell quotas following shifts in salinity (34 to 75, at 4°C), which suggests a potential osmoregulator function for both DMSP and DMSO. Stronger salinity shifts (up to 100) directly impact cell growth and induce a crash of the cultures. Combining the salinity (34 to 75) and temperature (4°C to –2.3°C) shifts induces higher increases of DMSP and DMSO cell quotas that also suggests an implication of both metabolites in a cryoprotectant system. Experimental cell quotas (including diatom Fragilariopsis cylindrus quotas from a previous study) are then used to reconstruct DMSP and DMSO profiles in sea ice based on the biomass and taxonomy. Finally, the complexity of the transposition of rates obtained in the experimental domain to the real world is discussed.

Potential of temperature- and salinity-driven shifts in diatom compatible solute concentrations to impact biogeochemical cycling within sea ice

Sea-ice algae are an important source of primary production in polar regions, yet we have limited understanding of their responses to the seasonal cycling of temperature and salinity. Using a targeted liquid chromatography-mass spectrometry-based metabolomics approach, we found that axenic cultures of the Antarctic sea-ice diatom, Nitzschia lecointei, displayed large differences in their metabolomes when grown in a matrix of conditions that included temperatures of –1 and 4°C, and salinities of 32 and 41, despite relatively small changes in growth rate. Temperature exerted a greater effect than salinity on cellular metabolite pool sizes, though the N- or S-containing compatible solutes, 2, 3-dihydroxypropane-1-sulfonate (DHPS), glycine betaine (GBT), dimethylsulfoniopropionate (DMSP), and proline responded strongly to both temperature and salinity, suggesting complexity in their control. We saw the largest (> 4-fold) response to salinity for proline. DHPS, a rarely studied but potential compatible solute, had the highest intracellular concentrations among all compatible solutes of ~85 mM. When comparing the culture findings to natural Arctic sea-ice diatom communities, we found extensive overlap in metabolite profiles, highlighting the relevance of culture-based studies to probe environmental questions. Large changes in sea-ice diatom metabolomes and compatible solutes over a seasonal cycle could be significant components of biogeochemical cycling within sea ice.

Dimethylated sulfur production in batch cultures of Southern Ocean phytoplankton

Dimethylsulfoniopropionate (DMSP) is a ubiquitous organic sulfur compound that underpins sulfur cycling in the marine environment and is the precursor to the climatically active gas dimethylsulfide (DMS). Modelling studies have identified the Southern Ocean as a DMS hot spot during summer, yet except for the bloom forming haptophyte Phaeocystis, little is known about sulfur production by other important members of the marine microbial community. Here, we measured DMSP concentrations and DMSP lyase activity (DLA), with corresponding carbon, nitrogen and Chl a content, in 15 species of Antarctic phototrophic phytoplankton (14 microalgae species and one cyanobacterium) and one phagotrophic flagellate. We found that 11 of the 16 species were able to produce DMSP and eight possess DLA. DMSP content ranged from 0.06 to 73 fmol cell−1 and estimated DMSP production rates ranged from 0.008 to 12.42 fmol cell−1 day−1. As expected, Phaeocystis was amongst the highest producers, however, contrary to expectation DMSP concentrations were high in several pennate diatom species, with intracellular concentrations between 1.85 and 46.6 mM. Here we present the first evidence that the cyanobacterium Synechococcus may be a DMSP producer, with the potential to contribute significantly to the DMSP pool. This study has provided the first analysis of DMSP production and DLA in a suite of phototrophic and phagotrophic species isolated from Antarctica, revealing the variability in DMSP concentrations across multiple strains and within genera and delivered new evidence for potential DLA in diatoms.

Modified VG-CL Detection System for Baseline Assessment of Dimethylsulphide and Dimethylsulphoniopropionate in Tropical Atlantic Seawater

Several studies have been carried out to measure the concentrations of dimethylsulphide (DMS) and dimethylsulphoniopropionate (DMSP) in coastal and open marine ecosystems. The present study attempted the fabrication of a cost-effective, highly sensitive and portable detection system based on vapour generation and chemiluminescence for a pilot assessment and determination of DMS and DMSP concentrations in tropical Atlantic seawater samples. The Sultan Beach and Badagry parts of the Atlantic Ocean were chosen as designated locations for this study. Vapour generation chemiluminescence (VG-CL) detection system is a device that can measure the concentration (nM) of DMS and DMSP by allowing DMS vapour which in turn reacts with ozone to produce chemiluminescence which can be detected by a photomultiplier (PMT). The mean concentrations of DMS and DMSP in the surface seawater at the sampling location were 5.80±0.71 to 19.40±0.57 nM and 11.00±0.42 to 34.70±1.13 nM, respectively. The average minimum and maximum concentrations of DMS and DMSP across the location were between 0 and 40.91 nM, respectively. This study serves as a baseline measurement of DMS concentrations in the tropical Atlantic Ocean (Lagos).

Genomic repertoire of Mameliella alba Ep20 associated with Symbiodinium from the endemic coral Mussismilia braziliensis

Bacteria associated with Symbiodinium may exert relevant roles in the Symbiodinium and the coral host. The bacterial isolate Ep20 was obtained from cell suspensions of Symbiodinium retrieved from the endemic coral Mussismilia braziliensis (Abrolhos Bank, Brazil). Here we aimed to analyze the genomic repertoire of Ep20 to gain insights into its possible roles in the coral holobiont. Ep20 enhanced the growth of Symbiodinium under controlled laboratory conditions, possibly through nitrogen fixation and vitamin production. The genome of Ep20 contains 5.5 Mbp (65% G + C content), 5397 genes, 53 tRNAs, and four rRNAs. Ep20 was identified as Mameliella alba, a member of the Roseobacter Clade Bacteria (RCB, Alphaproteobacteria). The genomic repertoire of Ep20 includes genes responsible for i. Aerobic Anoxygenic Photosynthesis (AAP), ii. Cofactors and vitamins (B12), iii. Gene Transfer Agents (GTAs), iv. Dimethylsulfoniopropionate (DMSP) metabolism, v. Carbon and Nitrogen fixation, and vi. Secondary metabolites (e.g., Terpenes). The genomic attributes of Ep20 hint at a possible mutualistic interaction with Symbiodinium, both in the free-living and in the coral holobiont lifestyles.

Shifts in dimethylated sulfur concentrations and microbiome composition in the red-tide causing dinoflagellate <i>Alexandrium minutum</i> during a simulated marine heatwave

Abstract. The biogenic sulfur compounds dimethyl sulfide (DMS), dimethyl sulfoniopropionate (DMSP) and dimethyl sulfoxide (DMSO) are produced and transformed by diverse populations of marine microorganisms and have substantial physiological, ecological and biogeochemical importance spanning organism to global scales. Understanding the production and transformation dynamics of these compounds under shifting environmental conditions is important for predicting their roles in a changing ocean. Here, we report the physiological and biochemical response of a robust strain of Alexandrium minutum, a dinoflagellate with the highest reported intracellular DMSP content, exposed to a 6 d increase in temperature mimicking mild and extreme coastal marine heatwave conditions (+4 and +12 ∘C). Under mild temperature increases (+4 ∘C), A. minutum growth was enhanced, with no measurable physiological stress response. However, under a very acute increase in temperature (+12 ∘C) triggering thermal stress, A. minutum growth declined, photosynthetic efficiency (FV∕FM) was impaired, and enhanced oxidative stress was observed. These physiological responses indicative of thermal stress were accompanied by increased DMS and DMSO concentrations followed by decreased DMSP concentration. At this temperature extreme, we observed a cascading stress response in A. minutum, which was initiated 6 h after the start of the experiment by a spike in DMS and DMSO concentrations and a rapid decrease in FV∕FM. This was followed by an increase in reactive oxygen species (ROS) and an abrupt decline in DMS and DMSO on day 2 of the experiment. A subsequent decrease in DMSP coupled with a decline in the growth rate of both A. minutum and its associated total bacterial assemblage coincided with a shift in the composition of the A. minutum microbiome. Specifically, an increase in the relative abundance of the operational taxonomic units (OTUs) matching Oceanicaulis (17.0 %), Phycisphaeraceae SM1A02 (8.8 %) and Balneola (4.9 %) as well as a decreased relative abundance of Maribacter (24.4 %), Marinoscillum (4.7 %) and Seohaeicola (2.7 %) were primarily responsible for differences in microbiome structure observed between temperature treatments. These shifts in microbiome structure are likely to have been driven by either the temperature itself, the changing physiological state of A. minutum cells, shifts in biogenic sulfur concentrations, the presence of other solutes, or a combination of all. Nevertheless, we suggest that these results point to the significant effect of extreme heatwaves on the physiology, growth and microbiome composition of the red-tide causing dinoflagellate A. minutum, as well as potential implications for biogenic sulfur cycling processes and marine DMS emissions.

Unprecedented DMSP Concentrations in a Massive Dinoflagellate Bloom in Monterey Bay, CA

AbstractThe organic sulfur compound dimethylsulfoniopropionate (DMSP) is synthesized by numerous species of marine phytoplankton, and its volatile degradation products are a major source of biogenic sulfur to the atmosphere. A massive bloom of the dinoflagellate Akashiwo sanguinea occurred in Monterey Bay, CA, USA, in the fall of 2016 and led to exceptionally high seawater DMSP concentrations that peaked at 4,240 nM. Bacterial consumption rates showed that only a small fraction of the DMSP standing stock flowed through the dissolved DMSP pool per day, contributing to the high DMSP concentrations and creating conditions conducive to production of dimethylsulfide (DMS). Conservative calculations of DMS yield from this persistent A. sanguinea bloom suggest substantial regional‐scale inputs of DMS‐sulfur to the atmosphere. Other recently reported major coastal blooms of A. sanguinea, along with indications that this species may benefit from climate change conditions, reveal a mechanism that could alter oceanic contributions to atmospheric sulfur pools.

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

AbstractVolatile 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.

Effect of Salinity on DMSP Production in Gambierdiscus belizeanus (Dinophyceae).

Dimethylsulfoniopropionate (DMSP) is produced by many species of marine phytoplankton and has been reported to provide a variety of beneficial functions including osmoregulation. Dinoflagellates are recognized as major DMSP producers; however, accumulation has been shown to be highly variable in this group. We explored the effect of hyposaline transfer in Gambierdiscus belizeanus between ecologically relevant salinities (36 and 31) on DMSP accumulation, Chl a, cell growth, and cell volume, over 12d. Our results showed that G. belizeanus maintained an intracellular DMSP content of 16.3pmol cell-1 and concentration of 139mM in both salinities. Although this intracellular concentration was near the median reported for other dinoflagellates, the cellular content achieved by G.belizeanus was the highest reported of any dinoflagellate thus far, owing mainly to its large size. DMSP levels were not significantly affected by salinity treatment but did change over time during the experiment. Salinity, however, did have a significant effect on the ratio of DMSP:Chl a, suggesting that salinity transfer of G.belizeanus induced a physiological response other than DMSP adjustment. A survey of DMSP content in a variety of Gambierdiscus species and strains revealed relatively high DMSP concentrations (1.0-16.4pmol cell-1 ) as well as high intrageneric and intraspecific variation. We conclude that, although DMSP may not be involved in long-term (3-12d) osmoregulation in this species, G.belizeanus and other Gambierdiscus species may be important contributors to DMSP production in tropical benthic microalgal communities due to their large size and high cellular content.