Dimethylsulfide In Water Research Articles

Factors Controlling DMS Emission and Atmospheric Sulfate Aerosols in the Western Pacific Continental Sea

AbstractThe western Pacific continental sea significantly influences the regulation of climate‐active gases budget and the burden of sulfate aerosols. An underway shipboard measurement device was used to determine the dimethyl sulfide (DMS) in the surface seawater and overlying atmosphere in the East China Continental Sea. The average concentration of DMS in atmosphere and seawater was 122.8 ± 86.2pptv and 6.47 ± 3.58 nmol L−1, respectively. The variation trend of surface water DMS in the western Pacific continental sea was influenced by the abundance and composition of phytoplankton under different ocean current systems, with a significant impact from eddies on DMS production in the South China Sea. By eliminating the influence of terrestrial sources and limiting air mass transport within the marine boundary layer, strong correlations were established between atmospheric DMS and air mass exposure to chlorophyll (Echl), as well as between aerosol methanesulfonic acid (MSA) and Echl. During the aerosol sampling period, the atmospheric DMS levels (1,057 ± 371 ng/m3) were significantly higher than MSA levels (46.3 ± 59.8 ng/m3) in the East China Sea, where the conversion of DMS to MSA was not affected by changes in DMS concentration. The sea‐to‐air fluxes of DMS varied over a wide range, from 0.02 to 156.0 μmol m−2 d−1, with an average of 14.35 ± 18.58 μmol m−2 d−1. Marine DMS emissions play a critical role in the formation of sulfur aerosols on the western Pacific continental shelf, accounting for 24.6 ± 7.6% (14.8%–37.8%) of the total sulfate aerosols.

A field study of chemical senses in bottlenose dolphins and pilot whales.

For most marine vertebrates, chemical cues provide crucial information during navigation and foraging, but their use by cetaceans is still poorly understood. In contrast to baleen whales, toothed whales (odontocetes) are scarcely equipped for chemoreception: they lack the conventional anatomical structures (i.e., olfactory epithelium, nerves and bulbs) involved in olfaction and have reduced taste buds on the tongue. Several behavioral studies have however shown that captive dolphins can perceive chemical solutions, including odorants, in their oral cavity. To investigate whether odontocetes could use infochemicals in their foraging ecology, we implemented a behavioral response experiment in wild bottlenose dolphins and long-finned pilot whales. We tested dimethyl sulfide (DMS) as a potentially attractive stimulus since it is a chemical signature of highly productive marine areas, known to attract several marine predators including fishes and seabirds. We assessed cetacean responses to DMS exposure by analyzing their movements and surface behaviors recorded by onboard observers. In both species, results did not reveal any significant attraction or behavioral reaction toward DMS when compared to a control chemical stimulus, apart from a short-distance response in bottlenose dolphins. These results suggest that while odontocetes may perceive DMS in water, it apparently does not play a significant role in their foraging ecology. Testing potentially more attractive compounds such as prey extracts with the present method and analyzing surface, underwater and acoustic responses would provide further insights on odontocete feeding behavior. It would also provide valuable clues to studies on the anatomical structures involved in their chemosenses.

Unravelling Surface Seawater DMS Concentration and Sea‐To‐Air Flux Changes After Sea Ice Retreat in the Western Arctic Ocean

AbstractThe receding of the seasonal ice cover in the Arctic due to climate change has been predicted by models to increase climate‐active biogenic trace gas emissions, specifically those of dimethylsulfide (DMS). However, insufficient DMS measurements are currently available to either support or refute this hypothesis and to fully understand the various responses of oceanic DMS in a rapidly changing Arctic Ocean environment. Here, we present high‐resolution surface water DMS data collected in the summer of 2014 in combination with a suite of ancillary variables including sea ice cover, salinity, and nutrients. We show that surface seawater DMS concentrations, generally below 0.5 nmol L−1, remained unchanged in the Canada Basin after sea ice retreat probably due to insufficient nutrients supply to the upper mixed layer and resulting low primary production. Moreover, in the Chukchi shelf region, DMS concentrations decreased following a phytoplankton bloom due to the rapid depletion and slow resupply of nutrients. Although the DMS sea‐to‐air fluxes were not high from a global perspective, they increased by a factor of 4‐fold after sea ice retreat in the Arctic Ocean high latitudes. This increase in DMS flux was mainly driven by increased wind speed. This work provides unique observations and insights on how surface seawater DMS and flux to the atmosphere may change in the future Arctic Ocean.

Characteristics of the surface water DMS and pCO2 distributions and their relationships in the Southern Ocean, southeast Indian Ocean, and northwest Pacific Ocean

AbstractOceanic dimethyl sulfide (DMS) is of interest due to its critical influence on atmospheric sulfur compounds in the marine atmosphere and its hypothesized significant role in global climate. High‐resolution shipboard underway measurements of surface seawater DMS and the partial pressure of carbon dioxide (pCO2) were conducted in the Atlantic Ocean and Indian Ocean sectors of the Southern Ocean (SO), the southeast Indian Ocean, and the northwest Pacific Ocean from February to April 2014 during the 30th Chinese Antarctic Research Expedition. The SO, particularly in the region south of 58°S, had the highest mean surface seawater DMS concentration of 4.1 ± 8.3 nM (ranged from 0.1 to 73.2 nM) and lowest mean seawater pCO2 level of 337 ± 50 μatm (ranged from 221 to 411 μatm) over the entire cruise. Significant variations of surface seawater DMS and pCO2 in the seasonal ice zone (SIZ) of SO were observed, which are mainly controlled by biological process and sea ice activity. We found a significant negative relationship between DMS and pCO2 in the SO SIZ using 0.1° resolution, [DMS] seawater = −0.160 [pCO2] seawater + 61.3 (r2 = 0.594, n = 924, p < 0.001). We anticipate that the relationship may possibly be utilized to reconstruct the surface seawater DMS climatology in the SO SIZ. Further studies are necessary to improve the universality of this approach.

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 < 0.001) and the Chlorophyll a/mixed layer depth ratio (r2 = 0.52, p < 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.

Photochemical production of carbonyl sulfide, carbon disulfide and dimethyl sulfide in a lake water

Photochemical production of carbonyl sulfide (COS), carbon disulfide (CS2) and dimethyl sulfide (DMS) was intensively studied in the water from the Aohai Lake of Beijing city. The lake water was found to be highly supersaturated with COS, CS2 and DMS, with their initial concentrations of 0.91±0.073nmol/L, 0.55±0.071nmol/L and 0.37±0.062nmol/L, respectively. The evident photochemical production of COS and CS2 in the lake water under irradiation of 365nm and 302nm indicated that photochemical production of them might be the reason for their supersaturation. The similar dependence of wavelength and oxygen for photochemical production of COS, CS2 and DMS implied that they might be from the same precursors. The water cage effect was found to favor COS production but inhibit CS2 and DMS formation, indicating that COS photochemical production was mainly from direct degradation of the precursors and the formation of CS2 and DMS needed intermediates via combination of carbon-centered radicals and sulfur-centered radicals. The above assumptions were further confirmed by simulation experiments with addition of carbonyls and amino acids (cysteine and methionine), and the photochemical formation mechanisms for COS, CS2 and DMS in water were derived from the investigations.

Validation of a Film Evaporator as a Wort Boiling System

The current article's topic is the use of a falling-film evaporator (down-draught vaporizer) as a boiler for flavor compound evaporation from wort. This particular proceeding is recommended because, with the lower temperature in a falling-film evaporator (here 62°C) dimethyl sulfide (DMS) evaporates at a higher volatility, and thus the process is less energy intensive than with the conventional boiling via internal or external boilers (100°C). The boiling process is calculated and validated by trials with both DMS in water and in wort in a pilot-scale plant. As a result, the use of a falling-film evaporator at lower temperatures (here 62°C) is interesting at high pump-around velocities.

Weak Correlation Between Methane Production and Abundance of Methanogens Across Three Brackish Marsh Zones in the Min River Estuary, China

Methane production is influenced by the abundance of methanogens and the availability of substrates. Sulfate-reducing bacteria (SRB) also play an important role in the anaerobic decomposition of organic matter. However, the relationships between methane production and abundance of methanogen and pore water substrates in estuarine brackish marshes are poorly characterized, and even to our knowledge, no published research has explored the relationship between methane production rate and pore water dimethyl sulfide (DMS) concentration. We investigated methane production rate, abundances of methanogens and SRB, sediment organic carbon contents, and concentrations of pore water substrates (acetate and DMS) and terminal electron acceptors (SO4 2−, NO3 −, and Fe3+) at a brackish marsh landscape dominated by Phragmites australis marsh, Cyperus malaccensis marsh, and Spartina alterniflora marsh in the Min River estuary, southeast China. The average rates of methane production over the entire 30 cm of the sediment profile (5 cm sampling interval) in the three marshes were 0.142, 0.058, and 0.067 μg g−1 day−1, respectively. The abundance of both methanogens and SRB in the sediment of the P. australis marsh with the highest sediment organic carbon content was higher than in the C. malaccensis and S. alterniflora marshes. Mean pore water DMS concentrations over the entire 30 cm of the sediment profile under the S. alterniflora marsh were higher than those in the C. malaccensis marsh and P. australis marsh. Methane production rate correlated weakly with the abundance of methanogens across the three marsh zones together, but did not correlate with the concentrations of pore water acetate and DMS. Our results suggest that the abundance of methanogens is controlled by sediment organic carbon supply, and further, methane production is affected by the abundance of methanogens in the subtropical estuarine brackish marshes.

The early events in the OH radical oxidation of dimethyl sulfide in water

The time-resolved Raman observation of a prototype of the hetero-atom three electron bonds (-X-OH) that often form on encounter of the OH radical with chemical species in water is reported. In spite of their wide chemical and biochemical importance, no experimental structural information exists, thus far, on any such bond in solution or in the gas phase. The nature of the >S-O bond formed on the reaction of the OH radical with dimethyl sulfide in water, investigated in the present work, would necessitate a reexamination of the existing reaction mechanisms in related biological systems and development of the appropriate computational methods.

Influence of regional climate forcing on surface water pCO2, ΔO2/Ar and dimethylsulfide (DMS) along the southern British Columbia coast

Oceanographic surveys of surface water hydrography, pCO2, biological O2 saturation (ΔO2/Ar) and dimethylsulfide (DMS) were conducted around Vancouver Island, B.C. during late spring of 2007 and 2010. Winter El Niño conditions during early 2010 resulted in strong downwelling and decreased sub-surface nutrient inventories relative to 2007, while reduced Fraser River input, high wind speeds and greater cloud cover led to relatively weak vertical stratification and decreased sea surface irradiance during the 2010 survey. Phytoplankton biomass (Chla) was significantly higher along the west coast of Vancouver Island (WCVI) during late May 2007, and we observed a strong biological imprint on surface gas distributions during this survey, with biologically induced O2 saturation in excess of 40%. Minimum pCO2 along the WCVI was 100ppm during the 2007 survey, and this region served as a moderate CO2 sink at the time of our sampling (mean sea-air flux of -3.2mmolCO2m−2d−1). By comparison, both pCO2 and ΔO2/Ar were much closer to atmospheric equilibrium during our 2010 survey. Despite these lower sea-air gradients, high wind speeds led to a significantly larger CO2 sink (13.4mmolm−2d−1) during the 2010 survey, and a greater uncoupling of ΔO2/Ar and pCO2 through differential gas exchange. Relative to the WCVI, pCO2 and ΔO2/Ar distributions showed smaller differences among cruises along the east coast of Vancouver Island (ECVI), where surface water properties were largely driven by physical circulation. Nonetheless, we did observe lower pCO2 and higher ΔO2/Ar in the Strait of Georgia during the 2010 survey, possibly due to a wind-driven mixing event which may have stimulated local primary productivity. DMS concentrations exhibited large ranges and significant small-scale spatial variability for both cruises, but mean DMS concentrations were more than three-fold higher along the WCVI during late May 2007. Higher wind speeds in late May 2010 led to greater DMS fluxes during our 2010 survey (10 vs. 5μmolm−2d−1 for 2010 and 2007, respectively) despite lower sea-air concentration gradients. For both cruises, about 40% of the variability in surface water DMS concentrations was explained by Chla/mixed layer depth ratios when data were binned to a spatial resolution of 0.25°. Based on our results, we discuss the potential linkages between regional climate variability and surface gases in coastal B.C. waters.

Vertical variability of seawater DMS in the South Pacific Ocean and its implication for atmospheric and surface seawater DMS

Shipboard measurements of atmospheric dimethylsulfide (DMS) and sea surface water DMS were performed aboard the R/V Onnuri across the South Pacific from Santiago, Chile to Fiji in February 2000. Hydrographic profiles of DMS, dissolved dimethylsulfoniopropionate (DMSP d), and particulate DMSP p in the upper 200 m were obtained at 16 stations along the track. Atmospheric and sea surface water DMS concentrations ranged from 3 to 442 pptv and from 0.1 to 19.9 nM, respectively; the mean values of 61 pptv and 2.1 nM, respectively, were comparable to those from previous studies in the South Pacific. The South Pacific Gyre was distinguished by longitudinal-vertical distributions of DMS, DMSP d, and DMSP p, which was thought to be associated with the characteristic modification of biological activities that occurs mainly due to significant change in water temperature. The averaged DMS maximum appeared at 40 m depth, whereas DMSP p and DMSP d maxima coincided with that of dissolved oxygen content at 60–80 m. The sea-to-air fluxes of DMS were estimated to be 0.4–11.3 μmol d −1 m −2 (mean = 2.8 μmol d −1 m −2). A fairly good correlation between atmospheric DMS and sea-to-air DMS flux indicated that atmospheric DMS concentration was more sensitive to change in physical parameters than its photochemical removal process or surface seawater DMS concentrations.

A Kirkwood-Buff derived force field for thiols, sulfides, and disulfides.

A force field has been developed for molecular simulations of methanethiol, dimethyl sulfide, and dimethyl disulfide mixtures. The force field specifically attempts to balance the solvation and self-association of these solutes in solution mixtures with methanol. The force field is based on the Kirkwood-Buff (KB) theory of solutions and is parametrized using the KB integrals obtained from the experimental activity coefficients for the solution mixtures. The transferability of the force field was tested and confirmed by the accurate prediction of the activity coefficients for methanethiol/dimethyl sulfide solutions, which were not used in the initial parametrization of the force fields. The ideality of this latter solution is excellently reproduced. The applicability of the force field to simulations in water was corroborated with a reasonably accurate prediction for the low solubility of dimethyl sulfide in water. The aggregation of methanol molecules at low methanol mole fractions displayed by all the mixtures is reproduced and further analyzed.

Limiting Separation Factors and Limiting Activity Coefficients for Hexanal, 2-Methylbutanal, 3-Methylbutanal, and Dimethylsulfide in Water at (98.1 to 99.0) °C

This work is a continuation of preceding work in which limiting separation factors of important wort flavor components in water at 100 °C were determined. In unpublished experiments, the vapor-liquid equilibrium (VLE) of the same aromatic compounds was also researched at atmospheric conditions. No significant differences between the previous published limiting separation factors at 100 °C and the unpublished ones at atmospheric conditions could be observed. Because of this fact, the results of the measurements were used to calculate residue curves during the atmospheric boiling of wort. This study was only investigated at atmospheric conditions. A recirculating Gillespie-type still was used to determine the limiting separation factor (K∞) for hexanal (x), 2-methylbutanal (x), 3-methylbutanal (x), and dimethylsulfide (x) in water (1 - x). Since the solutions were highly dilute (x < 10 -6 ), infinite dilution was assumed. As the investigated components do not have large absorbances in the UV region, they could not be analyzed by UV spectroscopy. Therefore, in contrary to the preceding work, they were analyzed by gas chromatography. As the boiling point of the solution only changed slightly at the given atmospheric conditions (ΔT ≤ 0.9 °C), the limiting separation factors were acquired assuming a constant average temperature of 98.55 °C. Thus, limiting activity coefficients were calculated at the same average temperature. The calculated limiting activity coefficient depends highly on the reliability of the vapor pressure data of the pure components.

Flux estimation of oceanic dimethyl sulfide around North America

Simultaneous measurements of atmospheric and surface water dimethyl sulfide (DMS) concentrations were taken aboard the icebreaker USCGC Polar Sea from July to October 1994, as part of a joint Canada/United States circumnavigation of North America, an expedition with a unique Arctic Ocean transect. Atmospheric DMS concentrations around North America varied between 0.25 and 50 nmol m−3 (mean = 5.1 nmol m−3, σ = 8.5 nmol m−3, n = 89) with highest values occurring near (south of) the Arctic ice edge. Surface water DMS concentrations ranged between 0.1 and 12.6 nmol L−1 (mean = 2.2 nmol L−1, σ = 2.7 nmol L−1, n = 46) with highest values in the western Arctic Ocean and off the U.S. east coast, near the Sargasso sea. In the Arctic Ocean, maximum concentrations in air and water were found along the ice edge in the Chukchi Sea region. Atmospheric DMS decay rates of 68% per day and 38% per day were deduced from observations between 70° and 76°N (continental shelf and slope of Chukchi Sea) on the west side and between 80° and 90°N (central Arctic Ocean) for the east side of the Arctic Ocean, respectively. Ocean to atmosphere flux estimates of DMS were determined using the Liss‐Merlivat empirical dependence of exchange coefficient on wind speed, DMS air concentrations, Henry's law constants, and DMS water concentrations. DMS fluxes varied between 0.0017 and 30 μmol m−2 d−1, respectively, with higher fluxes in regions with open water. The Arctic Ocean contributed 0.063 Tg S (DMS) (0.4% of DMS from the world oceans) during the summer of 1994. A simple one‐dimensional (1‐D) photochemical box model, applied to six case studies, showed that the atmospheric lifetime of DMS in the high Arctic was 2.5 to 8 days, whereas at 16°–33°N it was 1 to 2 days. Modeled DMS decay rates for these regions, using the 1‐D model, accounted for only 33% of the measured decay rate. This result also suggests that halogen chemistry, reactions with Br/BrO, may be an important sink for DMS in the Arctic atmosphere.

Dimethyl sulfide emissions to the atmosphere from lakes of the Canadian boreal region

Dimethyl sulfide (DMS) concentrations were measured over 2 years in 10 lakes situated in northwestern Ontario. Concentrations varied from 0.1 nmol L−1 to 100 nmol L−1 (geometric mean of 1.2 nmol L−1) during the ice‐free season (April to November) of 1995 and 1996. Shallow (1–5 m depth and 1–5 ha area) and medium depth (5–10 m depth and 5–15 ha area) lakes exhibited higher surface water DMS concentrations than deeper and larger lakes (32 m depth and 20–56 ha area). During the fall in the medium size lakes (5–12 m depth and &lt;15 ha area), DMS concentrations increased markedly by a factor of as much as 100 because of circulation of deeper, high‐DMS water from the hypolimnion (lake turnover). The estimated seasonal mean fluxes of DMS from shallow and medium depth lakes to the atmosphere ranged between 0.058 and 15 μmol S m−2 d−1 respectively. The shallow and medium depth lakes tend to release higher DMS than the large and deeper lakes. Extrapolation of flux estimates indicates that the lakes of the Canadian Boreal Shield emit 1.5 Gg yr−1 biogenic sulfur (DMS) to the atmosphere, and this is approximately 83% of the total annual biogenic sulfur (DMS) emissions from the Canadian Boreal Shield (lakes plus terrestrial). Compared to the annual anthropogenic emissions by five smelters in the boreal region, these emissions are small (0.08%).

Biogenic sulfur emissions from the Gulf of Saint Lawrence and assessment of its impact on the Canadian east coast

We measured dimethylsulfide (DMS) concentrations over a grid of 79 stations covering the central part of the Gulf of Saint Lawrence and during a 24‐hour sampling period at a fixed station, in August 1993. Surface water DMS concentrations ranged from &lt;0.9 to 9 nM over the sampling grid. DMS sea‐to‐air fluxes ranged from &lt;0,1 to 23 μmol m−2 d−1, with a mean of 4.7 μmol m−2 d−1 for August. Atmospheric DMS levels measured during the cruise ranged from less than 0.5 nmol m−3 (12 parts per trillion by volume, or pptv) to 25 nmol m−3 (625 pptv) with a mean value of 11.9 nmol m−3 (291 pptv). Results from the 24‐hour sampling at the fixed station show that ventilation may represent the most important sink for surface DMS when wind speeds exceed approximately 8 m s−1. The relative magnitude of the biogenic and anthropogenic S components was estimated by comparing sulfur emissions from the gulf to the sulfur emissions from surrounding continental regions and to a sulfur budget calculated by using a Lagrangian box model. The first approach suggests that DMS emissions from the gulf represented at least 4% of total (biogenic plus anthropogenic) sulfur emissions from the Atlantic Provinces in August 1993. A Lagrangian forward motion trajectory shows that these biogenic emissions would affect all the Maritime Provinces and a portion of eastern Quebec. The second approach suggests that the contribution of the gulf to the total sulfur flux may reach 13% when compared with the anthropogenic inflow of sulfur from the Atlantic Provinces impacting the Maritimes. When the transboundary inflow of sulfur from the United States is also taken into account, the contribution of the gulf becomes 8%. Thus DMS emissions from coastal waters may represent a significant source of sulfur to the atmosphere.

Determination of the Henry's law constant for dimethyl sulfide in seawater

This study describes a modified method to measure the Henry's law constant (Hc) of dimethyl sulfide (DMS) across air-water interface. A fixed amount of DMS was added into a 50 ml gas-tight glass syringe with air-water (seawater or distilled water) and equilibrated twice with different volumes of air but identical volume of water. The He of DMS in water could be determined by measuring the concentrations of DMS in the air phases of two equilibrium by gas chromtography. The He of DMS in seawater and distilled water determined by the modified method at 18°C were 0.069 and 0.056, respectively, and the relative standard deviation was less than 5%. The modified method was used to determine the effects of temperature on He of DMS in seawater and concentration of NaCl on He of DMS in freshwater.

Production and fate of dimethylsulfide and dimethylsulfoniopropionate in pelagic mesocosms:the role of sedimentation

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 131:275-286 (1996) - doi:10.3354/meps131275 Production and fate of dimethylsulfide and dimethylsulfoniopropionate in pelagic mesocosms: the role of sedimentation Osinga R, Kwint RLJ, Lewis WE, Kraay GW, Lont JD, Lindeboom HJ, van Duyl FC Elevated concentrations of dimethylsulfide (DMS) sometimes occur in sea water during phytoplankton blooms. To determine the factors controlling the concentration of DMS in sea water, the development and fate of a bloom dominated by Phaeocystis sp. was studied in relation to the production and fate of DMS and its precursor beta-dimethylsulfoniopropionate (DMSP) in a pelagic mesocosm experiment. The part of this study described here focused on the role of sedimentation of algae as a loss factor for DMSP and as a trigger mechanism for DMS production. A hypothesis tested was that high DMS concentrations occur after a mass release of DMSP from algae due to mass sedimentation followed by cell lysis on the mesocosm floor. This was studied by monitoring Phaeocystis cell numbers, chlorophyll a, particulate DMSP, dissolved DMSP and DMS in the water column, and by daily measurements of the sedimentation of Phaeocystis cells. We evaluated a technique for measuring DMSP indirectly as acrylate by high-performance liquid chromatography (HPLC). This method seemed to be hampered by DMSP-lyase activity of Phaeocystis sp. during sample processing, but gave good results when Phaeocystis was not dominant. Sedimentation rates of Phaeocystis sp. were found to be high and constantly related to the standing stock in the water column. The average sinking velocity of Phaeocystis cells was 1.4 m d-1. At the decline of the bloom, sedimentation accounted for approximately 50% of the observed loss of Phaeocystis biomass, which indicates that cell lysis may have been important as well at this time. The decline of the bloom did not result in an elevated DMS concentration. However, a significant peak in DMS was observed at the end of the exponential growth phase of the Phaeocystis bloom. It was concluded that the decline of a Phaeocystis bloom does not lead to an elevated DMS concentration in the water column. The continuously high sedimentation of living Phaeocystis cells suggests that, in these mesocosms, lysis after sedimentation was an important mechanism for release of DMSP from cells and, hence, production of DMS. Nevertheless, this mechanism in itself can not explain the strong fluctuations in the DMS concentration observed in this experiment. Phaeocystis . Sedimentation . DMS . DMSP Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 131. Publication date: February 08, 1996 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 1996 Inter-Research.

Experimental determination of the diffusion coefficient of dimethylsulfide in water

Estimates of the sea‐to‐air flux of dimethylsulfide (DMS) are based on sea surface concentration measurements and gas exchange calculations. Such calculations are dependent on the diffusivity of DMS (DDMS), which has never been experimentally determined. In this study the diffusivity of DMS in pure water was measured over a temperature range of 5°–30°C. The measurements were made using a dynamic diffusion cell in which the diffusing gas flows over one side of an agar gel membrane and the inert gas flows over the other side. The diffusion coefficient can be estimated from either time dependent or steady state analysis of the data, with an estimated uncertainty of less than 8% (1σ) in each measurement. A best fit to all the experimental results yields the equation DDMS (in cm2 sec−1) = 0.020 exp (−18.1/RT), where R = 8.314 × 10−3 kJ mole−1 K−1 and T is temperature in kelvin. The values of DDMS obtained in this study were 7–28% larger than estimates from the empirical formula of Hayduk and Laudie (1974) which has previously been used for DMS in gas exchange calculations. Applying these values to seawater results in an increase of less than 5% in the global oceanic flux of DMS.

Seasonal Variations in Dimethylsulfide in the Water of Maizuru Bay.

The concentration of biogenic dimethylsulfide (DMS) in the sea water in Maizuru Bay in one year (May 1986 to April 1987) ranged from 0.04 to 18.0μg DMS/l. Although these concentrations of DMS coincide slightly with the incidence of the concentration of chlorophyll a, a good correla-tion was obtained between concentrations of DMS and chlorophyll a in red tide waters of dinoflagellates such as Prorocentrum micans and Gymnodiniunm nagasakiense. Rough estimates for the average flux of DMS from coastal water to the atmosphere during the summer are of the order of 103μg S/m2.d, a 100-fold increase over the winter flux.