Dimethylsulfide Concentrations Research Articles

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.

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 meta-analysis of microcosm experiments shows that dimethyl sulfide (DMS) production in polar waters is insensitive to ocean acidification

Abstract. Emissions of dimethylsulfide (DMS) from the polar oceans play a key role in atmospheric processes and climate. Therefore, it is important to increase our understanding of how DMS production in these regions may respond to climate change. The polar oceans are particularly vulnerable to ocean acidification (OA). However, our understanding of the polar DMS response is limited to two studies conducted in Arctic waters, where in both cases DMS concentrations decreased with increasing acidity. Here, we report on our findings from seven summertime shipboard microcosm experiments undertaken in a variety of locations in the Arctic Ocean and Southern Ocean. These experiments reveal no significant effects of short-term OA on the net production of DMS by planktonic communities. This is in contrast to similar experiments from temperate north-western European shelf waters where surface ocean communities responded to OA with significant increases in dissolved DMS concentrations. A meta-analysis of the findings from both temperate and polar waters (n=18 experiments) reveals clear regional differences in the DMS response to OA. Based on our findings, we hypothesize that the differences in DMS response between temperate and polar waters reflect the natural variability in carbonate chemistry to which the respective communities of each region may already be adapted. If so, future temperate oceans could be more sensitive to OA, resulting in an increase in DMS emissions to the atmosphere, whilst perhaps surprisingly DMS emissions from the polar oceans may remain relatively unchanged. By demonstrating that DMS emissions from geographically distinct regions may vary in their response to OA, our results may facilitate a better understanding of Earth's future climate. Our study suggests that the way in which processes that generate DMS respond to OA may be regionally distinct, and this should be taken into account in predicting future DMS emissions and their influence on Earth's climate.

The satellite derived environmental factors and their relationships with dimethylsulfide in the East Marginal Seas of China

Abstract Biogenic dimethylsulfide (DMS) sea-to-air flux and its closely linked environment factors are studied in the East Marginal Seas of China (EMSC) (25°N-40°N, 120°E-130°E) from 2011 to 2015. Higher chlorophyll-a (CHL) up north during blooming season is due to the southeasterly wind brought more nutrients from the Changjiang River waters. The elevated CHL during autumn and winter periods down south is more related with the higher sea surface temperature (SST). The lower CHL in the middle region in the later half year was mainly influenced by terrestrial runoff and the diluted Changjiang River waters. The enriched Changjiang River discharges brought more nutrients to the Zhejiang coastal waters and enriched the local phytoplankton, where aerosol optical depth (AOD) had the highest correlation with CHL (0.96). Peak SST was in August and had a negative correlation with wind speed (WIND). With increased WIND up north, AOD reduced accordingly. Lower CHL in 2015 was mainly related to the southeastern wind brought less nutrient water from Open Sea during blooming season. DMS sea-to-air fluxes are calculated and compared with OUC (Ocean University of China) field data. The reasonable agreements are made. DMS concentrations ranged from 0.32 to 5.64 nM with a mean of 2.19 nM, it had high positive correlations with CHL in the summer and autumn periods. DMS sea-to-air fluxes ranged within 2.14–59.06 μmolm−2d−1 with a mean of 18.96 μmolm−2d−1. The elevated DMS sea-to-air fluxes in ECMS indicate the contributions of DMS emission in the study region cannot be ignored on the global climate evaluation.

Efficacy of photocatalytic air purifiers in reducing dimethyl sulfide malodor following cryopreserved peripheral blood stem cell infusion

Dimethyl sulfoxide (DMSO) is used as a cryoprotectant for peripheral blood stem cells (PBSC) preservation. Dimethyl sulfide (DMS) is a metabolite of DMSO secreted through patients' breath after PBSC infusion. It possesses malodor causing an unpleasant environment. We evaluated the efficacy of a photocatalyst environment purifier, which has the potential to lyse toxic substances, in reducing DMS malodor. High DMS concentration in the air after PBSC infusion rapidly decreased after operating the device. Our results suggest that photocatalytic reaction has the potential to reduce the DMS odor associated with PBSC infusion.

Seasonal Variations in Western North Atlantic Remote Marine Aerosol Properties

AbstractThe impact of ocean ecosystems on marine boundary layer aerosols and clouds has been the subject of much research but remains uncertain. Five experiments were recently conducted in the western North Atlantic to assess if the seasonally recurring phytoplankton bloom affects aerosol properties. These experiments include the second Western Atlantic Climate Study and four North Atlantic Aerosols and Marine Ecosystem Study cruises. Measurements of unheated and heated number size distributions, cloud condensation nucleus (CCN) concentrations, and aerosol composition were used to identify primary and secondary aerosol components that could be related to the state of the bloom. Only periods of clean marine air, as defined by radon, particle number concentrations, aerosol light absorption coefficient, and back trajectories, were included in the analysis. Nonvolatile material was found to be prevalent in the Aitken mode size range after heating to 230°, likely due to downward mixing from the free troposphere. CCN concentrations at 0.1% supersaturation were best correlated (r2 = 0.73) with accumulation mode nss SO4=. Sea spray aerosol was only correlated with CCN during November when bloom accumulation had not yet occurred and dimethylsulfide concentrations were at a minimum. The fraction of CCN attributable to sea spray aerosol was less than 20% during March, May/June, and September, indicating the limited contribution of sea spray aerosol to the CCN population of the western North Atlantic atmosphere. The strongest link between the plankton bloom and aerosol and cloud properties appears to be due to biogenic non‐sea salt SO4=.

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).

Sulfur and Nitrogen Gases in the Vapor Streams from Ore Cyanidation Wastes at a Sharply Continental Climate, Western Siberia, Russia

The article presents the results of the study of the vapor streams from sulfide-containing tailings after gold mining by cyanidation (Ursk waste heaps, Kemerovo region, Russia). The gas survey of sulfur dioxide, dimethyl sulfide, dimethyl sulfoxide, carbon disulfide, and N-containing substances concentrations was carried out using a portable device GANK-4 on a series of profiles covering the waste heaps and the surrounding area with simultaneous measurement of temperatures in the air and soil. The concentration maps-schemes of the studied gases in the surface layer were constructed. The high positive correlation of gases between themselves is established, which indicates similar mechanisms of their formation. The electrical resistivity tomography determined the internal structure of the waste heap. Active “breathing” zones were identified in which the maximum fluctuations in the concentrations of sulfur, selenium, and nitrogen-containing compounds in the near-surface air layer were recorded. Such zones are marked with lower resistances in comparison with other areas on the geo-electric profiles. There is an inverse correlation between the resistivity of the tailings and its temperature and a direct correlation between the concentration of gas in the air and the temperature of the soil. High concentrations of CS2, the volatile gas compound of the second hazard class, were found in the concentrations that exceed 6–8 times the daily average norm. Further investigation of the mine tailings seasonal transformation with the production of toxic gases deserves special attention due to high environmental risks and poor knowledge of this problem. The oxidation of ore cyanidation wastes in summer and methylation in winter due to seasonal temperature fluctuation lead to production of gases of great concern including toxic СS2.

Estimation of marine dimethyl sulfide emissions from East Asian seas and their impact on natural direct radiative forcing

This study investigated the impacts of marine dimethyl sulfide (DMS) emitted from East Asian seas on natural direct radiative forcing (DRF) based on a numerical modeling approach. The high-resolution (4 km) DMS emissions (i.e., DMS flux) were estimated from sea surface DMS concentrations and transfer velocity in the air-sea interface using satellite observations and model-predicted data during the period 2014–2016. We inputted these emission data into an aerosol optical model and then estimated the natural DRF of sulfate aerosols derived from the DMS flux (i.e., DMS-derived sulfate) using a radiative transfer model. The total mean DMS flux in the study area during the study period was estimated to be approximately 0.73 μmol/m2/day, with a maximum of 3.4 μmol/m2/day (December 2014) and a minimum of 0.12 μmol/m2/day (March 2014). The total mean negative forcing at the top of the atmosphere (DRFTOA) due to the DMS-derived sulfate was approximately −1.3 W m−2 in the target area during the study period. The monthly maximum (−2.8 W m−2) and minimum DRFTOA (−0.82 W m−2) occurred in December and March 2014, respectively, with the highest and lowest forcing at the surface and in the atmosphere during the same months. In terms of spatial distributions over the entire study area, negative DRFTOA exhibited a maximum of up to −8.8 W m−2 in the coastal sea near Shanghai, China, and a minimum of −0.6 W m−2 in the offshore sea of the East Sea, Korea. These increases and decreases in the natural DRFs were strongly attributed to the DMS fluxes, which were affected mainly by sea surface wind and/or partially by DMS concentrations, and relative humidity conditions in the study region.

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.

Field Assessment and determination of concentration levels of Dimethylsulphide in Tropical Seawater

Dimethylsulphide (DMS) is an important climatically reactive trace gas which is emitted from the seawater to the atmosphere. It undergoes various oxidative reactions to produce cloud condensation nuclei, which affect the earth radiation budget. DMS and its precursor dimethylsulphoniopropionate (DMSP) were measured using a modified vapour generation – chemiluminescence (VG-CL) detection system that was designed for this study. The chosen sampling locations used for the measurement were Nigeria Institute of oceanography and marine research (NIOMR) and ELEGUSHI. They are situated along the Gulf of Guinea. The modified VG-CL analyser was used for trace analysis of dimethylsulphide in the study area. The mean concentrations of DMS in the surface seawater at the two sampling locations ranged from 0 to 35.53±2.34 nM, 10.67±0.28 and 44.95±0.27 nM, respectively. The average minimum and maximum concentrations of DMS and DMSP across the two locations were between 0 and 44.95 nM, respectively. The concentrations of DMS and DMSP were compared across the sampling locations, and the observed pattern showed that DMS for ELEGUSHI has a higher concentration than NIOMR. The result further revealed that the concentration of the DMS is a function of the sea surface temperature (SST) of the aquatic ecosystem. The observed DMS concentration data of this study provides a baseline measurement for the tropical Atlantic Ocean (Lagos), thus a significant addition to the global DMS database.

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.

Role of Calanus sinicus (Copepoda, Calanoida) on Dimethylsulfide and Dimethylsulfoniopropionate Production in Jiaozhou Bay

AbstractThe role of copepod Calanus sinicus on the production of dimethylsulfide (DMS)/dimethylsulfoniopropionate (DMSP) in Jiaozhou Bay was evaluated in field measurements and laboratory experiments. Samples at 10 sites in the bay were collected monthly from June 2010 to May 2011 (except for March 2011), and zooplankton species composition was analyzed. Effects of C. sinicus grazing on DMS/DMSP production at different conditions (i.e., algal diets, food concentrations, and salinities) were assessed in the laboratory. Data from the field experiment showed that C. sinicus was the dominant copepod in Jiaozhou Bay (up to 123 individuals/m3 in May 2011) and preferred to graze on diatom. DMS and DMSP concentrations depend on not only phytoplankton abundance but also phytoplankton species and bacterial abundance. In the laboratory experiment, compared with Gymnodinium sp. or Emiliania huxleyi, C. sinicus feeding on Isochrysis galbana and Chaetoceros curvisetus exhibited increased DMS concentration, whereas high salinity inhibited DMS production. Copepod ingested 0.5%–35% of DMSP in filtered phytoplankton, and copepod DMSP ingestion turnover rate in Jiaozhou Bay was up to 29 pmol L−1 d−1. Although the microbial DMSP consumption rate was 10–2,620‐fold of copepod turnover rate, copepod grazing was still one of the important routes in DMSP loss processes through food chain. This study indicated that DMSP was transferred from phytoplankton to copepod body, fecal pellet, and seawater through copepod grazing. Our results provided important information to understand the biogeochemical cycle of DMSP in Jiaozhou Bay.

Variation of biogenic dimethylated sulfur compounds in the Changjiang River Estuary and the coastal East China Sea during spring and summer

Abstract The biogeochemical cycle of biogenic dimethylated sulfur compounds in oceans has received significant attention because of their critical role in the global climatic and atmospheric processes. The behavior of biogenic dimethylated sulfur compounds including dimethylsulfide (DMS), dimethylsulfoniopropionate (DMSP) and dimethylsulfoxide (DMSO) was measured in the waters of the Changjiang River Estuary and the coastal East China Sea during two cruises from 7 to 20 March 2016 and from 4 to 16 July 2016. The concentrations of DMS, particulate DMSP (DMSPp), dissolved DMSP (DMSPd), particulate DMSO (DMSOp) and dissolved DMSO (DMSOd) in the study area showed significant spatial and seasonal variation, with higher values in summer. DMS displayed significant relationships with DMSPp, DMSPd and DMSOp, and the dimethylated sulfur compound distributions showed similar patterns with that of chlorophyll a (Chl-a). The seasonal variation in DMSOd was inconspicuous compared to other sulfur compounds and its concentration inside the estuary was relatively high, suggesting an impact by anthropogenic activities and riverine inputs. Phytoplankton biomass and water mass mixing (upwelling and the Changjiang diluted water) played an important role in controlling the distributions of dimethylated sulfur compounds in the Changjiang River Estuary and the coastal East China Sea. The mean sea-to-air fluxes of DMS in this study area were 3.21 and 20.73 μmol m−2 d−1 in spring and summer, respectively. The study area was a net source for atmospheric DMS.

Bimetallic-based food sensors for meat spoilage: Effects of the accepting metallic unit in Fe(II)[sbnd]C[tbnd]N[sbnd]MA (MA = Pt(II) or Au(I)) on device selectivity and sensitivity

Technologies for monitoring meat spoilage are important to ensuring consumer safety. As dimethyl sulfide (DMS) is a reliable marker for meat freshness, sensitive and selective DMS sensors are of great interest. Herein, two trinuclear cyano-bridged bimetallic donor–acceptor ensembles, FeII(bpy)2(CN)2–[PtII(DMSO)Cl2]2 (1) and FeII(bpy)2(CN)2–[AuICl]2, were synthesized, and corresponding solid-supported sensors were fabricated to determine the effect of the acceptor metal (MA) on DMS detection. Changing MA from AuI to PtII improved the sensitivity and selectivity owing to changes in the relative thermodynamic stabilities of the complex and MA–DMS adduct. When applied to real meat samples, 1 exhibited a linear spectroscopic response to DMS, even in the presence of interfering compounds, with a method detection limit of 1.0 ppm. The total bacteria count and gas chromatography–mass spectrometry results revealed that the spectroscopic signal generated by 1 correlated with the microbial growth level and DMS concentration during meat spoilage.

Sea Ice and Water Mass Influence Dimethylsulfide Concentrations in the Central Arctic Ocean

Dimethylsulfide (DMS) is a biogenic trace gas with importance to aerosol formation. DMS is produced by microbial degradation of dimethylsulfoniopropionate (DMSP), an abundant metabolite in marine microalgae. We analyzed DMS and DMSP concentrations in surface water in the central Arctic Ocean during two expeditions north of 79°N in 2011 and 2015. We identified three regions, which were characterized by different DMS and DMSP concentrations, dependent on the regional water masses and the relative movement of sea ice and water to each other. In addition, correlations between DMS and DMSP and correlation of the two sulfur compounds to autotrophic biomass (as chlorophyll a) differed in the regions. In the area of the nutrient rich Atlantic water inflow and short contact of this water with sea ice, DMS is present in high concentrations and correlates to DMSP as well as chlorophyll a. At two stations, particularly high DMS concentrations were found in conjunction with under-ice phytoplankton biomass peaks. In contrast, in mixed Atlantic and Pacific water with strong polar influence, where long-term contact between sea ice and water causes persistent stratification, only little DMS is found. Further, the correlations to DMSP and chlorophyll a are lost and the ratio of DMS to DMSP is about one order of magnitude lower, pointing towards consumption of DMSP without the production of DMS. We conclude that the duration of sea ice influence and source of the surface water do not only lead to differences in phytoplankton productivity, resulting in different DMSP concentrations, but also influence microbial recycling of DMSP to DMS or other compounds. DMS production, as possible source for aerosols, is thus presumably lower in the strongly sea ice influenced central Arctic areas than what could be expected from DMSP concentration or biomass.

Sensitivity of Arctic sulfate aerosol and clouds to changes in future surface seawater dimethylsulfide concentrations

Abstract. Dimethylsulfide (DMS), outgassed from ocean waters, plays an important role in the climate system, as it oxidizes to methane sulfonic acid (MSA) and sulfur dioxide (SO2), which can lead to the formation of sulfate aerosol. Newly formed sulfate aerosol resulting from DMS oxidation may grow by condensation of gases, in-cloud oxidation, and coagulation to sizes where they may act as cloud condensation nuclei (CCN) and influence cloud properties. Under future global warming conditions, sea ice in the Arctic region is expected to decline significantly, which may lead to increased emissions of DMS from the open ocean and changes in cloud regimes. In this study we evaluate impacts of DMS on Arctic sulfate aerosol budget, changes in cloud droplet number concentration (CDNC), and cloud radiative forcing in the Arctic region under current and future sea ice conditions using an atmospheric global climate model. Given that future DMS concentrations are highly uncertain, several simulations with different surface seawater DMS concentrations and spatial distributions in the Arctic were performed in order to determine the sensitivity of sulfate aerosol budgets, CDNC, and cloud radiative forcing to Arctic surface seawater DMS concentrations. For any given amount and distribution of Arctic surface seawater DMS, similar amounts of sulfate are produced by oxidation of DMS in 2000 and 2050 despite large increases in DMS emission in the latter period due to sea ice retreat in the simulations. This relatively low sensitivity of sulfate burden is related to enhanced sulfate wet removal by precipitation in 2050. However simulated aerosol nucleation rates are higher in 2050, which results in an overall increase in CDNC and substantially more negative cloud radiative forcing. Thus potential future reductions in sea ice extent may cause cloud albedos to increase, resulting in a negative climate feedback on radiative forcing in the Arctic associated with ocean DMS emissions.

Patterns and drivers of dimethylsulfide concentration in the northeast subarctic Pacific across multiple spatial and temporal scales

Abstract. The northeast subarctic Pacific (NESAP) is a globally important source of the climate-active gas dimethylsulfide (DMS), yet the processes driving DMS variability across this region are poorly understood. Here we examine the spatial distribution of DMS at various spatial scales in contrasting oceanographic regimes of the NESAP. We present new high-spatial-resolution measurements of DMS across hydrographic frontal zones along the British Columbia continental shelf, together with key environmental variables and biological rate measurements. We combine these new data with existing observations to produce a revised summertime DMS climatology for the NESAP, yielding a broader context for our sub-mesoscale process studies. Our results demonstrate sharp DMS concentration gradients across hydrographic frontal zones and suggest the presence of two distinct DMS cycling regimes in the NESAP, corresponding to microphytoplankton-dominated waters along the continental shelf and nanoplankton-dominated waters in the cross-shelf transitional zone. DMS concentrations across the continental shelf transition (range < 1–10 nM, mean 3.9 nM) exhibited positive correlations to salinity (r=0.80), sea surface height anomaly (SSHA; r=0.51), and the relative abundance of prymnesiophyte and dinoflagellates (r=0.89). In contrast, DMS concentrations in nearshore coastal transects (range < 1–24 nM, mean 6.1 nM) showed a negative correlation with salinity (r=-0.69; r=-0.78) and SSHA (r=-0.81; r=-0.75) and a positive correlation to relative diatom abundance (r=0.88; r=0.86). These results highlight the importance of bloom-driven DMS production in continental shelf waters of this region and the role of prymnesiophytes and dinoflagellates in DMS cycling further offshore. In all areas, the rate of DMS consumption appeared to be an important control on observed concentration gradients, with higher DMS consumption rate constants associated with lower DMS concentrations. We compiled a data set of all available summertime DMS observations for the NESAP (including previously unpublished results) to examine the performance of several existing algorithms for predicting regional DMS concentrations. None of these existing algorithms was able to accurately reproduce observed DMS distributions across the NESAP, although performance was improved by the use of regionally tuned coefficients. Based on our compiled observations, we derived an average summertime distribution map for DMS concentrations and sea–air fluxes across the NESAP, estimating a mean regional flux of 0.30 Tg of DMS-derived sulfur to the atmosphere during the summer season.

Contrasting effects of acidification and warming on dimethylsulfide concentrations during a temperate estuarine fall bloom mesocosm experiment

Abstract. The effects of ocean acidification and warming on the concentrations of dimethylsulfoniopropionate (DMSP) and dimethylsulfide (DMS) were investigated during a mesocosm experiment in the Lower St. Lawrence Estuary (LSLE) in the fall of 2014. Twelve mesocosms covering a range of pHT (pH on the total hydrogen ion concentration scale) from 8.0 to 7.2, corresponding to a range of CO2 partial pressures (pCO2) from 440 to 2900 µatm, at two temperatures (in situ and +5 ∘C; 10 and 15 ∘C) were monitored during 13 days. All mesocosms were characterized by the rapid development of a diatom bloom dominated by Skeletonema costatum, followed by its decline upon the exhaustion of nitrate and silicic acid. Neither the acidification nor the warming resulted in a significant impact on the abundance of bacteria over the experiment. However, warming the water by 5 ∘C resulted in a significant increase in the average bacterial production (BP) in all 15 ∘C mesocosms as compared to 10 ∘C, with no detectable effect of pCO2 on BP. Variations in total DMSP (DMSPt = particulate + dissolved DMSP) concentrations tracked the development of the bloom, although the rise in DMSPt persisted for a few days after the peaks in chlorophyll a. Average concentrations of DMSPt were not affected by acidification or warming. Initially low concentrations of DMS (<1 nmol L−1) increased to reach peak values ranging from 30 to 130 nmol L−1 towards the end of the experiment. Increasing the pCO2 reduced the averaged DMS concentrations by 66 % and 69 % at 10 and 15 ∘C, respectively, over the duration of the experiment. On the other hand, a 5 ∘C warming increased DMS concentrations by an average of 240 % as compared to in situ temperature, resulting in a positive offset of the adverse pCO2 impact. Significant positive correlations found between bacterial production and concentrations of DMS throughout our experiment point towards temperature-associated enhancement of bacterial DMSP metabolism as a likely driver of the mitigating effect of warming on the negative impact of acidification on the net production of DMS in the LSLE and potentially the global ocean.

Global trend analysis in primary and secondary production of marine aerosol and aerosol optical depth during 2000–2015

The global trends in sea spray aerosol (SSA) emissions, dimethyl sulfide (DMS) flux from sea to air, and aerosol optical depth (AOD) during 2000–2015 were analyzed using the satellite-based, ECMWF reanalysis, and model-predicted data. The SSA emissions were estimated using a widely used whitecap method with a sea surface temperature (SST) dependence. The sea-to-air DMS fluxes were estimated by a thin film model based on the DMS concentration in seawater and its gas transfer velocity. The yearly global mean anomaly in DMS fluxes showed a significant downward trend during the study period, whereas the SSA emissions showed an upward trend. In terms of regional trends, the increases in SSA emissions during 2000–2015 occurred over the tropical southeastern Pacific Ocean and Southern Ocean, whereas any downward trends in SSA emissions were localized. The DMS fluxes during the study period showed a clear downward trend over most oceans, except for the strong upward trend at low latitudes. In general, the AOD from the MODerate resolution Imaging SpectroRadiometer (MODIS) showed upward trends across the entire Southern Hemisphere (SH), whereas there were downward trends in most areas of the Northern Hemisphere (NH). Therefore, the upward trend of AOD in the SH were derived mainly from the SSA emission trend, due to smaller contribution of anthropogenic sources in the SH.