Dimethylsulfide Production Rates Research Articles

Novel insights into dimethylsulfoniopropionate cleavage by deep subseafloor fungi

Dimethylsulfoniopropionate (DMSP), a key organic sulfur compound in marine and subseafloor sediments, is degraded by phytoplankton and bacteria, resulting in the release of the climate-active volatile gas dimethylsulfide (DMS). However, it remains unclear if dominant eukaryotic fungi in subseafloor sediments possess specific abilities and metabolic mechanisms for DMSP degradation and DMS formation. Our study provides the first evidence that fungi from coal-bearing sediments ∼2 km below the seafloor, such as Aspergillus spp., Chaetomium globosum, Cladosporium sphaerospermum, and Penicillium funiculosum, can degrade DMSP and produce DMS. In Aspergillus sydowii 29R-4-F02, which exhibited the highest DMSP-dependent DMS production rate (16.95 pmol/μg protein/min), two DMSP lyase genes, dddP and dddW, were identified. Remarkably, the dddW gene, previously observed only in bacteria, was found to be crucial for fungal DMSP cleavage. These findings not only extend the list of fungi capable of degrading DMSP, but also enhance our understanding of DMSP lyase diversity and the role of fungi in DMSP decomposition in subseafloor sedimentary ecosystems.

Dimethyl sulfide cycling in the sea surface microlayer in the southwestern Pacific – Part 2: Processes and rates

Abstract. As the sea surface microlayer (SML) is the uppermost oceanic layer and differs in biogeochemical composition to the underlying subsurface water (SSW), it is important to determine whether processes in the SML modulate gas exchange, particularly for climate active gases. Enrichment of dimethyl sulfide (DMS) and its precursor dimethylsulfoniopropionate (DMSP) has been reported in the SML, but it remains unclear how this is maintained whilst DMS is lost to the atmosphere. To examine this, a comprehensive study of DMS source and sink processes, including production, consumption, and net response to irradiance, was carried out in deck-board incubations of SML water at five locations in different water masses in the southwestern Pacific east of New Zealand. Net consumption of DMSP and production of DMS in the light and dark occurred at all sites. The net response of DMS and DMSP to irradiance varied between stations but was always lower than conversion of DMSP to DMS in the dark. In addition, DMS photolytic turnover was slower than reported elsewhere, which was unexpected given the high light exposure in the SML incubations. Although no relationships were apparent between DMS process rates and biogeochemical variables, including chlorophyll a, bacteria, and phytoplankton groups, net bacterial DMSP consumption was correlated with DMSP and DMS concentrations and also dinoflagellate and Gymnodinium spp. biomass, supporting the findings of a companion study that dinoflagellates play an important role in DMS cycling in the SML. However, net DMS production rates and accumulation were low relative to regional air–sea DMS loss, indicating that DMS cycling within the SML is unlikely to influence regional DMS emissions.

Production, distribution and flux of dimethyl sulfide in the East China Sea and its contribution to atmospheric sulfate aerosols

Environmental context Dimethyl sulfide is an important biogenic gas, released from ocean to atmosphere, which contributes to aerosol formation and can therefore affect global climate. Studies on dimethyl sulfide in both seawater and atmosphere have linked the atmospheric chemistry of dimethyl sulfide with its circulation in the marine environment. This study showed that these biogenic emissions contribute to the sulfur cycle and particulate production, deepening our understanding of their role in the East China Sea. Abstract Dimethyl sulfide (DMS) is identified as an essential biogenic sulfur compound in the ocean. Its oxidation products are thought to be important contributors to cloud condensation nuclei, thereby influencing the earth’s radiative balance and climate. The concentrations of DMS and its precursor, dimethylsulfoniopropionate (DMSP) were measured in seawater and sediment pore water in the East China Sea (ECS) during summer. In addition, dissolved DMSP (DMSPd) degradation rates, DMS production and consumption rates, and sea-to-air flux of DMS were determined, and the biogenic contribution to atmospheric non-sea-salt sulfate (nss-SO42−) was evaluated in PM2.5 and PM10 aerosols over the study area. The spatial distributions of DMS and DMSP were closely related to that of chlorophyll-a and decreased from the inshore to the offshore. The concentration of DMSPd in sediment pore water was significantly higher than that in bottom water, which indicated that sediment is a net source of DMSPd for bottom water. The biological incubation experiments showed that ~36.0 % of decomposed DMSPd was degraded into DMS, while 78.7 % of produced DMS was consumed by bacteria within the surface water. The sea-to-air flux of DMS varied from 1.30 to 31.84 μmol m−2 day−1, with an average of 7.45 ± 6.30 μmol m−2 day−1. Biogenic contributions of the ECS to total nss-SO42− were estimated to be 13.0 % ± 9.9 % in PM2.5 and 13.5 % ± 5.1 % in PM10 samples respectively, which indicated that marine DMS release cannot be neglected in the ECS during summer.

Identification of a functional dddD-Rh for dimethyl sulfide production in the Antarctic Rhodococcus sp. NJ-530.

Dimethylsulfoniopropionate (DMSP) is widespread in the oceans, and its biological metabolite, dimethyl sulfide (DMS), plays an important role in the atmosphere. The Antarctic region has become a hotspot in DMS studies due to the high spatial and temporal variability in DMS(P) concentration, but the level of bacterial DMS production remains unclear. In this study, a bacterium isolated from Antarctic floating ice, Rhodococcus sp. NJ-530, was found to metabolize DMSP into DMS, and the rate of DMS production was measured as 3.96 pmol·mg protein-1 ·h-1 . Rhodococcus sp. NJ-530 had a DddD-Rh enzyme containing two CaiB domains, which belonged to the CoA-transferase III superfamily. However, the DddD-Rh had a molecular weight of 73.21 kDa, which was very different from previously characterized DddD enzymes in sequence and evolution. In vitro assays showed that DddD-Rh was functional in the presence of acetyl-CoA. This was the first functional DddD from Gram-positive Actinobacteria. Moreover, a quantitative real-time polymerase chain reaction revealed that high temperature facilitated the expression of dddD-Rh, and changes of salinity had little effect on it. This study adds new evidence to the bacterial DMS production in the Southern Ocean and provides a basis for investigating the metabolic mechanism of DMSP in extreme environments.

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.

Distribution, Occurrence, and Fate of Biogenic Dimethylated Sulfur Compounds in the Yellow Sea and Bohai Sea During Spring

AbstractThe spatial distributions of biogenic dimethylated sulfur compounds (BDSCs), including dimethylsulfide (DMS), dimethylsulfoniopropionate (DMSP), and dimethylsulfoxide, were determined in the Yellow Sea and Bohai Sea during a survey in April–May 2014 and the occurrence and fate of BDSCs in the surface seawater were investigated. The concentrations of DMS and DMSP were significantly correlated with the stocks of chlorophyll a and a decreasing trend was observed from the inshore to the offshore areas. In situ incubation experiments indicated that more than half of the degraded dissolved DMSP (DMSPd) was transformed into DMS. Irradiation experiments showed that the photooxidation of DMS under ultraviolet B, ultraviolet A, and visible light accounted for 23.9%, 71.8%, and 4.3% of the total photooxidation of DMS, respectively. The sea‐to‐air fluxes of DMS ranged from 0.24 to 34.11 μmol m−2 day−1 with a mean of 8.84 μmol m−2 day−1. A comparison of the DMS production rate and main removal rates indicated that bioproduction cannot completely maintain the removal of DMS and might not be the only but the primary source of DMS in the surface seawater. Additionally, the average turnover times of microbial consumption, photooxidation, and sea‐to‐air exchange of DMS were 1.53, 1.16, and 4.28 day and the contributions of the three removal pathways were 40.0%, 41.2%, and 18.8% respectively; this indicated that microbial consumption and photooxidation played dominant roles in controlling the removal of DMS from the surface seawater.

Modelling dimethylsulfide diffusion in the algal external boundary layer: implications for mutualistic and signalling roles.

Dimethylsulfide (DMS), a dominant organic sulfur species in the surface ocean, may act as a signalling molecule and contribute to mutualistic interactions between bacteria and marine algae. These proposed functions depend on the DMS concentration in the vicinity of microorganisms. Here, we modelled the DMS enrichment at the surface of DMS-releasing marine algal cells as a function of DMS production rate, algal cell radius and turbulence. Our results show that the DMS concentration at the surface of unstressed phytoplankton with low DMS production rates can be enriched by <1 nM, whereas for mechanically stressed algae with high activities of the enzyme DMSP-lyase (a coccolithophore and a dinoflagellate) DMS cell surface enrichments can reach ~10 nM, and could potentially reach μM levels in large cells. These DMS enrichments are much higher than the median DMS concentration in the surface ocean (1.9 nM), and thus may attract and support the growth of bacteria living in the phycosphere. The bacteria in turn may provide photoactive iron chelators (siderophores) that enhance algal iron uptake and provide algal growth factors such as auxins and vitamins. The present study highlights new insights on the extent and impact of microscale DMS enrichments at algal surfaces, thereby contributing to our understanding of the potential chemoattractant and mutualistic roles of DMS in marine microorganisms.

Concentrations and cycling of DMS, DMSP, and DMSO in coastal and offshore waters of the Subarctic Pacific during summer, 2010‐2011

AbstractConcentrations of dimethylsulfide (DMS), measured in the Subarctic Pacific during summer 2010 and 2011, ranged from ∼1 to 40 nM, while dissolved dimethylsulfoxide (DMSO) concentrations (range 13‐23 nM) exceeded those of dissolved dimethyl sulfoniopropionate (DMSP) (range 1.3–8.8 nM). Particulate DMSP dominated the reduced sulfur pool, reaching maximum concentrations of 100 nM. Coastal and off shore waters exhibited similar overall DMS concentration ranges, but sea‐air DMS fluxes were lower in the oceanic waters due to lower wind speeds. Surface DMS concentrations showed statistically significant correlations with various hydrographic variables including the upwelling intensity (r2 = 0.52, p &lt; 0.001) and the Chlorophyll a/mixed layer depth ratio (r2 = 0.52, p &lt; 0.001), but these relationships provided little predictive power at small scales. Stable isotope tracer experiments indicated that the DMSP cleavage pathway always exceeded the DMSO reduction pathway as a DMS source, leading to at least 85% more DMS production in each experiment. Gross DMS production rates were positively correlated with the upwelling intensity, while net rates of DMS production were significantly correlated to surface water DMS concentrations. This latter result suggests that our measurements captured dominant processes driving surface DMS accumulation across a coastal‐oceanic gradient.

Processes driving seasonal variability in DMS, DMSP, and DMSO concentrations and turnover in coastal Antarctic waters

AbstractThis study presents new measurements of the concentrations and turnover rates of dimethyl sulfide (DMS), dimethylsulfoniopropionate (DMSP), and dimethyl sulfoxide (DMSO) in coastal waters near Palmer Station, Antarctica, during the spring and summer of 2012–2013. Using several novel analytical and experimental techniques, we document variability in DMS, DMSP, and DMSO (DMS/P/O) concentrations and quantify dominant production and removal terms in the mixed layer DMS budget. Our results demonstrate considerable seasonal variability in the concentration of DMS (range 0–20 nM), total DMSP (8–160 nM), and total DMSO (4–160 nM). Over the seasonal cycle, dissolved DMSP concentrations were well correlated with total DMSP concentrations and the abundance of Phaeocystis antarctica, while DMSO concentrations (total and dissolved) were well correlated with DMS concentrations. DMSP cleavage from the dissolved pool (mean rate = 5.5 nM d−1) and release from microzooplankton grazing (mean 5.6 nM d−1) were the dominant sources of DMS, with smaller DMS production rates associated with DMSO reduction from the dissolved pool (mean 2.6 nM d−1) and krill grazing (mean 0.82 nM d−1). Specific rate constants for DMSP cleavage were inversely related to net primary production. Bacterial uptake was a primary contributor to DMS removal (mean −12 nM d−1), and we observed a significant correlation between bacterial production and gross DMS loss rate constants. Estimated sea‐air flux and photo‐oxidation constituted secondary DMS sinks. Our experimental and analytical methods provide insight into the DMS/P/O cycle at Palmer Station, and a starting point for future studies examining inter‐annual DMS/P/O variability in coastal Antarctic waters.

Vernal distribution and turnover of dimethylsulfide (DMS) in the surface water of the Yellow Sea

AbstractThe spatial and interannual variations of dimethylsulfide (DMS) and its precursors, dissolved and particulate dimethylsulfoniopropionate (DMSP), were discussed on the basis of field observations in the surface waters of the Yellow Sea during spring 2007. Maxima of dimethylated sulfur compounds and low chlorophyll a concentrations were found in the central southern Yellow Sea, whereas low concentrations of DMS and DMSP were detected at the boundary between the northern and southern parts of the Yellow Sea. This frontal region is influenced by active water currents, air‐sea interface exchanges, and biological turnover. The horizontal variations in DMS production and consumption rates showed a decreasing tendency from the coastal to offshore areas mainly due to the complicated biological features. DMS positively correlated with dissolved CH4 and CO2 but negatively correlated with nutrients (nitrite and phosphate). Particulate DMSP concentrations and DMS production rates positively correlated with dinoflagellate abundances but negatively correlated with diatom cell densities. DMS and DMSP concentrations, as well as DMS production and consumption rates, exhibited approximately 2.0–2.8 fold increases from 2005 to 2012. This finding was likely caused by shifts in the phytoplankton communities from diatoms to dinoflagellates and the increases in abundances of zooplankton and bacteria. Average sea‐to‐air DMS fluxes were estimated to be 8.12 ± 1.24 µmol·(m−2·d−1), and DMS microbial consumption was approximately 1.68 times faster than the DMS sea‐air exchange. These findings imply that biological consumption, relative to ventilation, is a predominant mechanism in DMS removal from the surface water.

Biological production and spatial variation of dimethylated sulfur compounds and their relation with plankton in the North Yellow Sea

The concentrations of dimethylated sulfur compounds and chlorophyll a, as well as biological production and consumption rates of dimethylsulfide (DMS), were measured in the surface water of the North Yellow Sea (NYS, 37–40°N to 121–124°E) in winter 2007. Surface DMS, dissolved and particulate dimethylsulfoniopropionate (DMSPd and DMSPp) concentrations in the study area increased significantly from offshore to inshore sites, with the average values of 2.00, 4.52 and 7.21nM, respectively. The biological production and consumption rates of DMS were estimated, with the average values of 5.41 and 3.84nMd−1, respectively. The spatial variation of chlorophyll a was consistent with that of DMS and DMSP, as well as with that of DMS biological production, suggesting that phytoplankton biomass might play an important role in controlling the distribution of DMS and DMSP in the study area. According to the collective data of dimethylated sulfur compounds and DMS biological conversion in China Seas, the dimethylated sulfur compounds concentrations in the NYS during winter were a factor of 2 and 1.3 higher than those in the East China Sea and South China Sea, respectively. Less DMS (DMSP) in NYS was released in winter than that in spring and summer, which could be attributed to the shift in phytoplankton community composition dominated by diatoms to non-diatoms from winter to summer. Quantitative comparison analysis pointed to DMSPp rather than DMSPd as an important precursor of DMS in the surface water. The estimated sea-to-air fluxes of DMS using Liss and Merlivat (LM86), Wanninkhof (W92) and Nightingale (N2000) formulae were 2.72, 5.12 and 4.28μmolm−2d−1, respectively. In the surface water, the biological turnover time of DMS varied from 0.21 to 1.73d with an average of 0.83d, which was about 5.43-fold faster than the mean DMS sea–air turnover time (3.12d), implying that microbial consumption was a main sink of DMS in the surface water.

Spatial distribution of dimethylsulfide and dimethylsulfoniopropionate in the Yellow Sea and Bohai Sea during summer

The distributions of dimethylsulfide (DMS) and its precursor dimethylsulfoniopropionate (DMSP) in surface water of the Yellow Sea and the Bohai Sea were studied during June 2011. The mean concentrations and ranges of DMS, dissolved DMSP (DMSPd), and particulate DMSP (DMSPp) in surface waters were 6.85 (1.60-12.36), 7.25 (2.28-19.05) and 61.87 (6.28-224.01) nmol/L, respectively. There were strong correlations between DMSPp and chlorophyll a in the Bohai Sea and the North Yellow Sea, respectively, and concentrations of DMS and DMSP were high, with a relatively high proportion of dinoflagellates, in the region of the South Yellow Sea Cold Water Mass. Results show that phytoplankton biomass and species composition were important factors that controlled the distribution of DMS and DMSP. Complex environmental factors, including nutrients, transparency, and terrestrial runoff, might also influence the variability in DMS and DMSP. Biological production and consumption rates of DMS in the Bohai Sea were higher than those in the Yellow Sea. DMS production rates were closely correlated with DMSPd concentrations. DMS and DMSP exhibited obvious diel variations, with high concentrations occurring in the late afternoon (16:00-19:00) and low concentrations occurring during the night, implying that the intensity of solar radiation had a significant influence on these variations. Size distributions of chlorophyll a and DMSPp were also investigated and large nanoplankton (5-20 mu m), mainly diatoms, contributed significantly to chlorophyll a and DMSPp at most stations. The average sea-to-air flux of DMS in the study area was estimated to be 11.07 mu mol/(m(2)center dot d) during the summer.

A meta‐analysis of oceanic DMS and DMSP cycling processes: Disentangling the summer paradox

AbstractThe biogenic volatile compound dimethylsulfide (DMS) is produced in the ocean mainly from the ubiquitous phytoplankton osmolyte dimethylsulfoniopropionate (DMSP). In the upper mixed layer, DMS concentration and the daily averaged solar irradiance are roughly proportional across latitudes and seasons. This translates into a seasonal mismatch between DMS and phytoplankton biomass at low latitudes, termed the “DMS summer paradox,” which remains difficult to reproduce with biogeochemical models. Here we report on a global meta‐analysis of DMSP and DMS cycling processes and their relationship to environmental factors. We show that DMS seasonality reflects progressive changes in a short‐term dynamic equilibrium, set by the quotient between gross DMS production rates and the sum of biotic and abiotic DMS consumption rate constants. Gross DMS production is the principal driver of DMS seasonality, due to the synergistic increases toward summer in two of its underlying factors: phytoplankton DMSP content (linked to species succession) and short‐term community DMSP‐to‐DMS conversion yields (linked to physiological stress). We also show that particulate DMSP transformations (linked to grazing‐induced phytoplankton mortality) generally contribute a larger share of gross DMS production than dissolved‐phase DMSP metabolism. The summer paradox is amplified by a decrease in microbial DMS consumption rate constants toward summer. However, this effect is partially compensated by a concomitant increase in abiotic DMS loss rate constants. Besides seasonality, we identify consistent covariation between key sulfur cycling variables and trophic status. These findings should improve the modeling projections of the main natural source of climatically active atmospheric sulfur.

Seasonal variation and biogeochemical cycling of dimethylsulfide (DMS) and dimethylsulfoniopropionate (DMSP) in theYellowSea andBohaiSea

AbstractThe concentrations of dimethylsulfide (DMS), dimethylsulfoniopropionate (DMSP) and chlorophylla(Chl‐a) as well as the size distribution of particulate DMSP (DMSPp) were determined in the Yellow Sea (YS) and Bohai Sea (BS) during two cruises from 1 to 20 November 2012 and from 21 June to 11 July 2013. Besides, the biological production and consumption rates of DMS and the degradation rates of dissolved DMSP (DMSPd) were also measured. The concentrations of DMS and DMSP showed a significant seasonal variation with higher values in summer, which corresponded well with the seasonal change of Chl‐ain the study area. Both DMS and DMSPp concentrations were significantly correlated with Chl‐alevels, implying that phytoplankton biomass might play an important role in controlling the distributions of DMS and DMSP in the study area. The size‐fractionation research showed that nanophytoplankton (5–20 μm) contributed to most of Chl‐aand DMSPp in autumn and summer. The average biological production and consumption rates of DMS during summer were 13.35 and 9.80 nmol L−1d−1, respectively, which were much higher than those during autumn. The degradation rates of DMSPd during summer ranged from 7.10 to 21.70 nmol L−1d−1, with an average of 14.71 nmol L−1d−1, which was nearly equal to the average biological production rate (13.35 nmol L−1d−1) of DMS. The average sea‐to‐air flux of DMS in the YS and BS were 12.06 and 20.81 μmol m−2d−1in autumn and in summer, respectively, which were much higher than the values reported in the ocean.

Macroscale patterns of the biological cycling of dimethylsulfoniopropionate (DMSP) and dimethylsulfide (DMS) in the Northwest Atlantic

The influence of the seasonal development of microplankton communities on the cycling of dimethylsulfide (DMS) and its precursor dimethylsulfoniopropionate (DMSP) was investigated along a South–North gradient (36–59°N) in the Northwest (NW) Atlantic Ocean. Three surveys allowed the sampling of surface mixed layer (SML) waters at stations extending from the subtropical gyre to the Greenland Current during May, July and October 2003. Pools and transformation rates of DMSP and DMS were quantified and related to prevailing physical and biochemical conditions, phytoplankton abundance and taxonomic composition, as well as bacterioplankton abundance and leucine uptake. The South–North progression of the diatom bloom, a prominent feature in the NW Atlantic, did not influence the production of DMS whereas conditions in the N Atlantic Drift lead to a persistent bloom of DMSP-rich flagellate-dominated phytoplankton community and high net DMS production rates. Macroscale patterns of the observed variables were further explored using principal component analysis (PCA). The first axis of the PCA showed a strong association between the spatio-temporal distribution of DMSP and the abundance of several phytoplankton groups including dinoflagellates and prymnesiophytes, as well as with microbial-mediated DMSPd consumption and yields and rates of the conversion of DMSP into DMS. The second axis revealed a strong association between concentrations of DMS and SML depth and photosynthetically active radiation, a result supporting the prominent role of solar radiation as a driver of DMS dynamics.

Optimisation of a fast DMS sensor (FDS) for real time quantification of dimethyl sulfide production by algae

Production of dimethyl sulfide (DMS) from marine samples is often quantified using gas chromatography techniques. Typically, these are labour intensive and have a slow sample turnover rate. Here we demonstrate the use of a portable fast DMS sensor (FDS) that utilises the chemiluminescent reaction of DMS and ozone to measure DMS production in aqueous samples, with a maximum frequency of 10 Hz. We have developed a protocol for quantifying DMS production that removes potential signal interference from other biogenic trace gases such as isoprene (2-methyl-1,3-butadiene) and hydrogen sulfide. The detection limit was 0.89 pM (0.02 ppbv) when using a DMS standard gas mixture. The lowest DMS production rates quantified with the FDS and verified using conventional gas chromatography with flame photometric detection (GC-FPD) were around 0.01 nmol min−1. There was a strong correlation in DMS production when comparing the FDS and GC-FPD techniques with a range of marine samples (e.g., r2 = 0.94 for Emiliania huxleyi). However, the combined dataset showed the FDS measured 22% higher DMS production than the GC-FPD, with the differences in rates likely due to interfering gases, for example hydrogen sulfide and isoprene. This possible overestimation of DMS production is smaller than the two-fold difference in DMS production between day and night samples from a culture of E. huxleyi. The response time of the instrument to changes in DMS production is method dependent (e.g., geometry of incubation vessel, bubble size) and was approximately 4 min under our conditions when using a culture of E.huxleyi (800 ml) with aeration at 100 ml min−1. We suggest the FDS can reduce sample handling, is suitable for short- and long-term measurements of DMS production in algal cultures, and will widen the range of DMS research in marine environments.

High concentrations and turnover rates of DMS, DMSP and DMSO in Antarctic sea ice

[1] The vast Antarctic sea-ice zone (SIZ) is a potentially significant source of the climate-active gas dimethylsulfide (DMS), yet few data are available on the concentrations and turnover rates of DMS and the related compounds dimethylsulfoniopropionate (DMSP) and dimethylsulfoxide (DMSO) in sea ice environments. Here we present new measurements characterizing the spatial variability of DMS, DMSP, and DMSO concentrations across the Antarctic SIZ, and results from tracer experiments quantifying the production rates of DMS from various sources. We observed extremely high concentrations (>200 nM) and turnover rates (>100 nM d−1) of DMS in sea-ice brines, indicating intense cycling of DMS/P/O. Our results demonstrate a previously unrecognized role for DMSO reduction as a major pathway of DMS production in Antarctic sea ice.

Distribution and microbial metabolism of dimethylsulfoniopropionate and dimethylsulfide during the 2007 Arctic ice minimum

[1] The distribution and biological cycling of the climate active trace gas dimethylsulfide (DMS) and its algal precursor dimethylsulfoniopropionate (DMSP) were characterized at 20 stations across the Canadian High Arctic during fall 2007. Transformation rates of DMSP and production rates of DMS from dissolved DMSP (DMSPd) were measured during 3 h onboard incubations with radioactively labeled 35S-DMSP. Particulate DMSP (DMSPp) in surface waters varied between 2 and 39 nmol L−1 and increased with chlorophyll a (Chl a) concentrations (r = 0.84). DMS concentrations in surface waters ranged from 0.05 to 0.8 nmol L−1 and were positively correlated with DMSPp (r = 0.89) and Chl a (r = 0.74). The DMSPd loss rate constant varied from 0.01 to 0.14 h−1 and was also positively correlated with Chl a concentrations (r = 0.67). The turnover time of the DMSPd pool varied between 0.3 and 3.4 days (mean = 0.96 day). Bacterial DMS production varied between 0.01 and 0.51 nmol L−1 d−1 (mean = 0.14 nmol L−1 d−1). Assuming local steady state conditions at the time scale of a day, the turnover time of the DMS pool based only on production from DMSPd was ∼6 days at the sampling stations. This long turnover time suggests that DMS production was dominated by nonbacterial processes during our study. Our results show that DMS production could persist at low rates in late fall under ice-free conditions. The magnitude of this production appears to be limited by the low algal and bacterial production prevailing at that time.

Diagnostic modeling of dimethylsulfide production in coastal water west of the Antarctic Peninsula

The rate of gross biological dimethylsulfide (DMS) production at two coastal sites west of the Antarctic Peninsula, off Anvers Island, near Palmer Station, was estimated using a diagnostic approach that combined field measurements from 1 January 2006 through 1 March 2006 and a one-dimensional physical model of ocean mixing. The average DMS production rate in the upper water column (0–60m) was estimated to be 3.1±0.6nMd−1 at station B (closer to shore) and 2.7±0.6nMd−1 at station E (further from shore). The estimated DMS replacement time was on the order of 1d at both stations. DMS production was greater in the mixed layer than it was below the mixed layer. The average DMS production normalized to chlorophyll was 0.5±0.1(nMd−1)/(mgm−3) at station B and 0.7±0.2(nMd−1)/(mgm−3) at station E. When the diagnosed production rates were normalized to the observed concentrations of total dimethylsulfoniopropionate (DMSPt, the biogenic precursor of DMS), we found a remarkable similarity between our estimates at stations B and E (0.06±0.02 and 0.04±0.01(nMDMSd−1)/(nMDMSP), respectively) and the results obtained in a previous study from a contrasting biogeochemical environment in the North Atlantic subtropical gyre (0.047±0.006 and 0.087±0.014(nMDMSd−1)/(nMDMSP) in a cyclonic and anticyclonic eddy, respectively). We propose that gross biological DMS production normalized to DMSPt might be relatively independent of the biogeochemical environment, and place our average estimate at 0.06±0.01(nMDMSd−1)/(nMDMSPt). The significance of this finding is that it can provide a means to use DMSPt measurements to extrapolate gross biological DMS production, which is extremely difficult to measure experimentally under realistic in situ conditions.

Bacterial DMSP metabolism during the senescence of the spring diatom bloom in the Northwest Atlantic

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 369:1-11 (2008) - DOI: https://doi.org/10.3354/meps07664 FEATURE ARTICLE Bacterial DMSP metabolism during the senescence of the spring diatom bloom in the Northwest Atlantic Anissa Merzouk1,*, Maurice Levasseur2, Michael Scarratt3, Sonia Michaud3, Martine Lizotte2, Richard B. Rivkin4, Ronald P. Kiene5 1University of British Columbia, Earth and Ocean Sciences/Oceanography, 1461-6270 University Boulevard, Vancouver, British Columbia V6T 1Z4, Canada 2Université Laval, Département de biologie (Québec-Océan), Pavillon Alexandre-Vachon, Quebec, Quebec G1K 7P4, Canada 3Fisheries and Oceans Canada, Maurice Lamontagne Institute, 850 Route de la mer, Mont-Joli, Quebec G5H 3Z4, Canada 4Ocean Sciences Centre, Memorial University of Newfoundland, St. John’s, Newfoundland A1C 5S7, Canada 5University of South Alabama, Department of Marine Sciences, Mobile, Alabama 36688, USA *Email: amerzouk@eos.ubc.ca ABSTRACT: The impact of the decline of the vernal bloom on the bacterial metabolism of dimethylsulfoniopropionate (DMSP), the precursor of dimethylsulfide (DMS), was investigated during a 7 d Lagrangian study conducted in the Northwest Atlantic in spring 2003. Daily variations in bacterial leucine incorporation, dissolved DMSP (DMSPd) uptake and DMS production rates were measured in the surface mixed layer (SML) and in the deep chlorophyll a maximum (DCM) that formed as the bloom collapsed. Seawater samples were amended with 35S-DMSPd, and the products of bacterial DMSPd degradation were measured during 3 h on-board incubations. The gradual decrease in phytoplankton biomass and diatom abundance measured in the SML was accompanied by a sharp doubling of the bacterial abundance and a peak in leucine incorporation rate on Day 2, suggesting that bacteria responded to a transient pulse in dissolved organic matter. Bacterial DMSPd uptake and DMS production were highest on Days 1 and 2 (1.2 and 0.10 nmol l-1 h-1, respectively), but rapidly decreased by Day 3, suggesting that DMSPd was becoming a less important substrate for the growing bacterial assemblage as other substrates became available. Bacterial DMSPd uptake and DMS production rates were also low in the DCM despite very high DMS yields (40 to 50%), showing that neither the decline of the diatom spring bloom in the SML nor the accumulation of cells in the DCM resulted in a stimulation of bacterial DMSP metabolism or accumulation of DMS. The present study provides new field evidence for the potential uncoupling between bacterial production and DMS dynamics likely due to variations in the availability of other S-containing organic compounds released during the decay of phytoplankton blooms. KEY WORDS: DMSP cycling · Bacterial metabolism · Bloom senescence · Northwest Atlantic Ocean Full text in pdf format Information about this Feature Article NextCite this article as: Merzouk A, Levasseur M, Scarratt M, Michaud S, Lizotte M, Rivkin RB, Kiene RP (2008) Bacterial DMSP metabolism during the senescence of the spring diatom bloom in the Northwest Atlantic. Mar Ecol Prog Ser 369:1-11. https://doi.org/10.3354/meps07664Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 369. Online publication date: October 13, 2008 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2008 Inter-Research.