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Dimethyl sulfide (DMS) is an important and dominant trace gas that is transferred from the ocean to the atmosphere; however, the production of DMS from marine algae is still rudimentary, with the enzymatic cleavage of dimethylsulfoniopropionate (DMSP) to DMS and acrylic acid (AA), one of the main considered pathways. Dissolved DMSP (DMSPd) was supplied to batch cultures of Prorocentrum minimum at different algal growth stages and the kinetics of overall DMSPd consumption and DMS (AA) production were investigated. The kinetics of overall DMSPd consumption and DMS (AA) production from DMSPd were different during the growth cycle. The cultures displayed Michaelis–Menten-type kinetics for DMS production during the entire growth period, which yielded an apparent half-saturation constant (Km(app)) value of 37.8 ± 12.8 μM and a maximum rate (Vmax) value of 75.6 ± 12.2 nmol min−1 (1010 cells)−1. The production rates of AA had a nearly linear fit over the concentration range of the added DMSPd except during mid-exponential growth phase. A Km(app) value of 1.73 ± 0.75 μM and a Vmax value of 2.36 ± 0.12 μmol min−1 (1010 cells)−1 were observed. The ratio of DMS/AA increased with the concentration of the added DMSPd, which was less than 12% during the entire growth period. The low ratios of DMS/(DMSP + AA), which ranged from 0.01 to 1.83%, demonstrate that degradation of DMSP tends to take a non-DMS-production pathway. The ratios of AA/(DMSP + AA) varied from 9 to 95% during the stationary phase and from 6 to 69% during the senescent phase and declined with substrate concentration when different concentrations of DMSPd were added. The degradation ratios of DMSPd were related to the initial concentrations of DMSPd. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Production of dimethylsulfoniopropionate (DMSP), dimethylsulfide (DMS), and acrylic acid (AA) from 22 marine microalgae representing six phyla were examined at different growth stages. The concentrations of DMSP, DMS, and AA per cell in the media showed significant changes during the whole growth period, and the highest concentrations were found at the stationary growth phase or the senescent phase. Different species had different concentration levels of DMSP, DMS, and AA, among which Pyrrhophyta, Bacillariophyte, and Chrysophyta had relatively large release. The highest concentrations of DMSP, DMS, and AA were 56.70, 0.86, and 44.60 fmol cell−1 in Scrippsiella trochoidea , Prymnesiacee , and Karenia mikimotoi , respectively. The ratios of DMS/DMSP and AA/(DMSP+AA) in the 22 marine microalgae differed dramatically over the growth cycle. The DMS/DMSP ratios were <25%, indicating that only a small fraction of DMSP was converted to DMS by enzymatic cleavage. Moreover, there was a higher ratio of enzymatic degradation of DMSP in the senescent growth stage. The AA/(DMSP+AA) ratio, representing the degradation ratio of DMSP, increased significantly at the beginning of growth period and then decreased. Hence, the changes in these ratios could approximately illustrate the degradation mechanism of DMSP among diverse species at different growth phases. • High DMSP, DMS and AA concentrations were detected in Pyrrophyta and Bacillariophyta. • The maximum concentrations of DMSP and DMS appeared in the stationary growth stage. • The highest release of AA was observed in the early exponential growth period. • The maximum value of DMSP enzymatic degradation appeared in late growth phase. [ABSTRACT FROM AUTHOR]

To examine the sulfate assimilation and reduction process and the regulation of illumination, diatom Phaeodactylum tricornutum and dinoflagellate Amphidinium carterae were selected for continuous simulation incubation under different photon flux densities (PFDs) (54, 108 and 162 μmol photons m−2 s−1), and concentration variations of related sulfur compounds sulfate, dimethylsulfoniopropionate (DMSP), dimethylsulfide (DMS) and acrylic acid (AA) in the culture system were observed. The optimal PFD for the growth of two microalgae was 108 μmol photons m−2 s−1. However, the maximum sulfate absorption occurred at 162 μmol photons m−2 s−1 for P. tricornutum and at 54 μmol photons m−2 s−1 for A. carterae. With the increase of PFD, the release of DMSP by P. tricornutum decreased while A. carterae increased. The largest release amount of DMS was 0.59 ± 0.05 fmol cells−1 for P. tricornutum and 2.61 ± 0.89 fmol cells−1 for A. carterae under their optimum growth light condition. The sulfate uptake of P. tricornutum was inhibited by the addition of amino acids, cysteine had a greater inhibitory effect than methionine, and the absorption process was controlled by light. The intermediate products of sulfur metabolism had an up–control effect on the sulfate uptake process of P. tricornutum. However, the addition of amino acids had no obvious effect on the sulfate absorption of A. carterae. • Illumination regulated sulfate assimilation of P. tricornutum and A. carterae. • 108 μmol photons m−2 s−1 was the optimum light condition for the algal growth. • Related sulfur compounds concentrations varied under different illumination. • Sulfur metabolic intermediates inhibited the sulfate uptake of P. tricornutum. • Sulfur metabolic intermediates had no obvious regulative law on A. carterae. [ABSTRACT FROM AUTHOR]

Acrylic acid (AA), a short-chain fatty acid found in the ocean, is derived from the microbial cleavage of dimethylsulfoniopropionate in addition to terrestrial input. The aqueous photochemical transformation of AA in natural seawater, artificial seawater, and Milli-Q water was studied under artificial light (using a photochemical reactor) and natural light (by exposure to sunlight). A degradation study on field seawater was conducted inside and outside Jiaozhou Bay, which is located in the north of China. Kinetic studies showed that the degradation and reaction rate of AA in natural seawater were obviously higher than those in the other aqueous media under artificial and natural light, with the degradation characteristics in artificial seawater and Milli-Q water being similar. The degradation and reaction rate of AA in natural seawater significantly increased with decreased concentration. AA in different media exhibited relatively lower reaction rates under natural light than those under artificial light. However, AA at different concentrations had similar degradation and reaction rates under these two irradiation types. Visible light seemed more efficient for the degradation reaction than ultraviolet A and ultraviolet B rays. The concentrations and degradation of AA inside and outside the Jiaozhou Bay showed significantly seasonal variations, and the photochemical and microbial degradation both showed the maximum rates in autumn. The photochemical reaction rates were found to be lower than the microbial degradation rates in four seasons. The photochemical degradation inside the bay was always lower than that outside. The photochemical transformation of AA depended on seawater composition and field conditions. [ABSTRACT FROM AUTHOR]

As the degradation products of dimethylsulfoniopropionate (DMSP), dimethylsulfide (DMS) and acrylic acid (AA) are crucial to the sulfur cycle in the ocean. However, the biogeochemical processes of DMSP, DMS, and AA remain unclear. A monthly investigation was conducted to determine the DMSP, DMS, and AA concentrations and related parameters in the surface water of Jiaozhou Bay, a semi-enclosed bay in the western Yellow Sea, from December 2010 to November 2011. The monthly mean concentrations of DMSP, DMS, and AA were in the ranges of 5.02–27.25 nmol L−1, 0.41–3.14 nmol L−1, and below the detection limit–301.75 nmol L−1, respectively, showing significant seasonal variations with higher concentrations in summer than in autumn. The results were attributed to a combination of biogenic factors, including phytoplankton, zooplankton, and bacteria, as well as environmental factors, such as temperature and nutrients. The DMSP, DMS, and AA concentrations were not significantly correlated with chlorophyll a and bacterial abundance because of the influence of the community structure and anthropogenic activities. DMS was mainly produced by the enzymatic cleavage of DMSP, whereas AA was affected primarily by terrigenous input. The monthly mean sea-to-air fluxes of DMS ranged from 0.74 (in Apr) to 6.55 (in Jan) μmol m−2 d−1 with an average of 2.80 μmol m−2 d−1. • DMSP, DMS, and AA showed significant seasonal variations. • Biogenic sulfur variation was a combination of biogenic and environmental factors. • The monthly mean sea-to-air fluxes of DMS was estimated. [ABSTRACT FROM AUTHOR]