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Spatiotemporal distributions of dissolved acrylic acid (AAd) and related biogenic sulfur compounds including dimethylsulfide (DMS) and dissolved and total dimethylsulfoniopropionate (DMSPd and DMSPt) were investigated in the Bohai Sea (BS) and Yellow Sea (YS) during summer and winter. AAd and DMS production from DMSPd degradation and AAd degradation were analyzed. Significant seasonal variations in AAd and DMS(P) were observed. AAd exhibited similar distributions during summer and winter; i.e., relatively high values of AAd occurred in the BS and the northern YS, and the concentrations decreased from inshore to offshore areas in the southern YS. Due to strong biological production from DMSP and abundant terrestrial inputs from rivers in summer, the AAd concentrations in the surface seawater during summer (30.01 nmol L -1) were significantly higher than those during winter (14.98 nmol L -1). The average concentration sequence along the transects during summer (AAd > DMSPt > DMS > DMSPd) showed that particulate DMSP (DMSPp) acted as a DMS producer and that terrestrial sources of AAd were present; in contrast, the sequence in winter was AAd > DMSPt > DMSPd > DMS. High values of AAd and DMS(P) were mostly observed in the upper layers, with occasional high values at the bottom. High AAd concentrations in the porewater, which could be transported to the bottom water, might result from the cleavage of intracellular DMSP and reduce bacterial metabolism in sediments. In addition, the production and degradation rates of biogenic sulfur compounds were significantly higher in summer than in winter, and the removal of AAd was primarily attributed to microbial consumption. Other sources of AAd existed aside from the production from DMSPd. [ABSTRACT FROM AUTHOR]

Abstract: The distributions of dimethylsulfide (DMS), dimethylsulfoniopropionate (DMSP), and acrylic acid (AA) were investigated in the Changjiang Estuary during winter (dry season) and summer (wet season) 2014 and in the East China Sea (ECS) during summer 2015. The rates of dissolved DMSP (DMSPd) degradation with DMS and AA production, DMS degradation, and AA degradation in the ECS were also studied. Significant seasonal variations in DMS(P) and AA concentrations were observed in the Changjiang Estuary with higher values during the wet season than during the dry season. The maximum ratio of AA/chlorophyll a (Chl a) occurred at the mouth of the Changjiang Estuary due to the combined effects of production from DMSP and terrestrial inputs from the Changjiang Estuary. The distributions of DMS(P) and AA in the ECS were dramatically influenced by the Kuroshio Current and the upwelling caused by the Taiwan Warm Current. The ratios of DMS(P)/Chl a and AA/Chl a exhibited similar patterns in the surface seawater of the ECS, which indicated that phytoplankton species and biomass might play important roles in controlling the distributions of DMS(P) and AA. In vertical profiles, high values of AA emerged in the upper water column and bottom seawater of the Changjiang Estuary. Meanwhile, the maxima of DMS(P) and AA generally appeared in the surface or euphotic layer, whereas their minima arose in the bottom seawater of the ECS. The degradation rates of DMSPd, DMS, and AA in the inshore waters were higher than those in the open sea. [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]