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Nitric oxide (NO) is an atmospheric pollutant and climate forcer as well as a key intermediary in the marine nitrogen cycle, but the ocean’s NO contribution and production mechanisms remain unclear. Here, high-resolution NO observations were conducted simultaneously in the surface ocean and the lower atmosphere of the Yellow Sea and the East China Sea; moreover, NO production from photolysis and microbial processes was analyzed. The NO sea–air exchange showed uneven distributions (RSD = 349.1%) with an average flux of 5.3 ± 18.5 × 10–17 mol cm–2 s–1. In coastal waters where nitrite photolysis was the predominant source (89.0%), NO concentrations were remarkably higher (84.7%) than the overall average of the study area. The NO from archaeal nitrification accounted for 52.8% of all microbial production (11.0%). We also examined the relationship between gaseous NO and ozone which helped identify sources of atmospheric NO. The sea-to-air flux of NO in coastal waters was narrowed by contaminated air with elevated NO concentrations. These findings indicate that the emissions of NO from coastal waters, mainly controlled by reactive nitrogen inputs, will increase with the reduced terrestrial NO discharge.

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.

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.

Environmental context Blooms of Ulva prolifera have recurred annually in the Yellow Sea since 2007, causing economic losses and severe ecological problems. We conducted laboratory incubation experiments to examine the effects of temperature and nutrients on its biogenic sulfur emissions during its decline period. Increasing temperature and nutrients affected the decay of U. prolifera, resulting in respective decreased and increased emission of biogenic sulfur compounds. Abstract The Ulva prolifera blooms have recurred annually in the Yellow Sea (YS) since 2007, causing huge economic losses and severe ecological problems. So far, few studies have investigated the release of volatile biogenic sulfur compounds by the U. prolifera blooms. In this study, laboratory incubation experiments were conducted to examine the effects of temperature and nutrient concentrations on the emissions of biogenic sulfur compounds during the green tide decline period. Under simulated conditions, higher incubation temperatures and nutrient concentrations promoted the decay of U. prolifera. When the incubation temperature was increased from 20 °C to 25 °C, the mean concentrations of dimethylsulfide (DMS), dissolved dimethylsulfoniopropionate (DMSPd) and particulate dimethylsulfoniopropionate (DMSPp) in the culture medium decreased by ~20 %, 55 % and 20 % respectively; in addition, these values increased by ~40 %, 70 % and 240 % respectively when exogenous nutrients were added to the culture medium. Moreover, a high concentration of nitrate (NO3–) (>50 μM) could promote the release of biogenic sulfur by U. prolifera in the absence of other nutrients. The findings of this study provide insight into the roles of macroalgae on changes to the environment and shed light on the potential impact of DMSP and other degradation products of DMS produced by the green tide on the environment and ecosystem.

Environmental context Atmospheric trace gases called volatile halocarbons (VHCs) significantly contribute to ozone depletion and global warming. The oceans are a primary source of VHCs, and concentrations and fluxes of selected VHCs in the Yellow Sea and East China Sea were measured. These data, and the influence of marine environmental factors on these parameters, provide information which will permit the assessment of the marine contribution of VHC behaviour and impact. Abstract Concentrations of five volatile halocarbons (VHCs), that is, chloroform (CHCl3), trichloroethylene (C2HCl3), tetrachloroethylene (C2Cl4), bromoform (CHBr3) and chlorodibromomethane (CHBr2Cl), were measured in the South Yellow Sea (SYS) and East China Sea (ECS) during autumn in 2011. The average (min–max) concentrations of CHCl3, C2HCl3, C2Cl4, CHBr2Cl and CHBr3 in surface seawater were 63.91 (24.63–361.23), 28.46 (1.82–85.77), 21.04 (9.85–89.31), 20.92 (7.98–59.89) and 75.91 (0.04–537.04) pmol L−1 respectively. The five VHCs exhibited a point distribution in autumn with clearly defined patterns in certain areas. In the vertical profiles, the highest concentrations of VHCs generally appeared in the upper mixing layer. Different VHCs were correlated with different environmental parameters, such as temperature, salinity, chlorophyll a (Chl-a), nutrient levels and bacteria. These results revealed that the sources of these VHCs were influenced by the Yangtze River effluent and Kuroshio waters as well as the biogenic release. Diurnal bimodal cycles were obvious in the concentrations of the five VHCs in the ECS. In general, concentrations peaked around noon, likely owing to biological production and photochemical mechanisms, and a secondary peak occurred around midnight, possibly resulting from a combination of respiration, zooplankton feeding and tidal action. The estimated sea-to-air fluxes showed that the study area was a net source of the five VHCs in the atmosphere during the study period.

As the boundary interface between the atmosphere and ocean, the sea-surface microlayer (SML) plays a significant role in the biogeochemical cycles of dissolved organic matter (DOM) and macronutrients in marine environments. In our study, the optical properties of DOM were compared between the sub-surface water (SSW) and the SML during spring, summer and winter in the East China Sea (ECS) and the Yellow Sea (YS). In addition, photoexposure experiments were designed to compare photochemical degradation processes of DOM between the SML and the SSW. Chromophoric DOM (CDOM), fluorescent DOM, dissolved organic carbon, chlorophyll a (Chl a), picoplankton, nutrients and bacteria were frequently enriched in the SML. The enrichment factors (EFs) of tryptophan-like component 4 were significantly higher than other fluorescence components; the longer wavelength absorption values of CDOM showed higher EFs in the SML, and a more significant relationship between CDOM and Chl a in the SML, indicating that autochthonous DOM was more strongly enriched in the SML than the terrestrial DOM. Higher EFs were generally observed in the SML in the off-shore regions than in the coastal regions, and CDOM in the SML was photobleached more after relatively strong irradiation, as also indicated by the lower percentages of humic-like DOM and lower specific UV absorbance values (SUVA254) in the SML than the SSW. Compared to the SSW, the elevated nutrients may stimulate phytoplankton growth, biological activity and then production of abundant fresh autochthonous DOM in the SML. Our results revealed a new enrichment model for exploring the air–sea interface environment, which can explain the more autochthonous properties of DOM in the SML than the SSW.

Dimethylsulfide (DMS) plays an important role in the sulfur biogeochemical cycle and cloud formation on Earth. In the past few decades, coastal shellfish breeding facilities have developed rapidly and the number of hypoxic environments has increased rapidly in shallow coastal areas. However, the effects of hypoxia and marine animal feeding on DMS production remain controversial. The Yantai offshore area is an important shellfish breeding area where hypoxia occurs frequently in the bottom seawater during the summer. In this study, we found that particle dimethylsulfoniopropionate (DMSPp) and attached bacteria play dominated roles in DMS production and average DMS concentration in coastal shellfish farming region was 38.84% higher than that in non-shellfish farming region during the breeding period. Different from the zooplankton “sloppy feeding”, the shellfish “filter-feeding” first repackages the phytoplanktonic DMSP into fecal DMSP, and then degrades DMSPp into DMS by attracting attached bacteria. Based on field investigations and hypoxia simulation experiment, we found that hypoxic stress had no significant effect on the production or consumption of DMS in seawater and the decline rates of DMS at the sediment-water interface between the oxic and hypoxic groups were nearly identical. Therefore, no significant difference in average DMS concentration was observed between the mild hypoxic area and the other sea areas during the summer. Meanwhile, although the DMSP-degrading bacteria presented different responses to hypoxia, little difference was observed in the entire microbial community structure or the DMSP catabolizing genes.

The Pacific Ocean plays an important role in regulating the budget of climatically active gases and the burden of sulfate aerosols. Here, a field investigation was conducted to clarify the key processes and factors controlling climatically active gases, including dimethyl sulfide (DMS), carbonyl sulfide (OCS), carbon disulfide (CS

Most marine copiotrophic bacteria can produce extracellular enzymes to degrade biopolymers into bio-available smaller solutes, while oligotrophic bacteria usually cannot. Bacterial extracellular enzymes and enzymatic products can be a common resource that could be utilized by both copiotrophs and oligotrophs; when present, oligotrophs may outcompete the enzyme-producing copiotrophs. However, copiotrophs and oligotrophs consistently coexist in the ocean. How they maintain coexistence has still not been experimentally studied. In this study, the interaction and coexistence of a copiotroph and an oligotroph, isolated from the same surface seawater sample and utilizing the same proteinaceous substrate, were experimentally investigated. The copiotroph could secrete extracellular proteases to degrade and then utilize the proteinaceous substrate. The oligotroph was unable to utilize the proteinaceous substrate by itself, but could grow by using the hydrolysate amino acids. The copiotroph outcompeted the oligotroph by adsorbing the amino acids quickly and having a higher growth rate in the rich medium. The oligotroph survived by adapting to low concentration of nutrients. The copiotroph and oligotroph were able to maintain long-term (up to 142 days) coexistence in the laboratory. This study indicates that differences in the utilization of different concentrations of nutrients can drive the coexistence of marine copiotrophs and oligotrophs.

Methyl iodide (CH3I) is an important trace greenhouse gas in the atmosphere and an ozone-depleting substance. The influence of different environmental factors, such as the duration of illumination; the strength of illumination; the concentrations of humic acid, ferric ion (Fe3+), and iodide ion (I−); and pH, on the photochemical production of CH3I in artificial seawater (ASW) were tested by simulated solar irradiation. In addition, Yangtze River Estuary waters from inshore to offshore were used to explore the relationship between the photochemical production of CH3I and different sources of dissolved organic matter (DOM) in natural sea-water (NSW). The results revealed that higher concentrations of humic acid and I−, as well as higher strengths of illumination and longer illumination durations, promoted the photochemical formation of CH3I in ASW. The addition of Fe3+ accelerated the photochemical production of CH3I, but high concentrations of Fe3+ inhibited the formation of CH3I. Experiments on NSW obtained from the Yangtze River estuary spiked when concentrations of DOM were high, confirming that DOM plays an important role in facilitating the photochemical production of CH3I within the Yangtze River Estuary. The photochemical production of CH3I in the seawater was significantly higher under light conditions relative to dark conditions, indicating that illumination accelerated the production of CH3I.

Dimethylsulfoniopropionate (DMSP) is an important marine osmolyte. Aphotic environments are only recently being considered as potential contributors to global DMSP production. Here, our Mariana Trench study reveals a typical seawater DMSP/dimethylsulfide (DMS) profile, with highest concentrations in the euphotic zone and decreased but consistent levels below. The genetic potential for bacterial DMSP synthesis via the dsyB gene and its transcription is greater in the deep ocean, and is highest in the sediment.s DMSP catabolic potential is present throughout the trench waters, but is less prominent below 8000 m, perhaps indicating a preference to store DMSP in the deep for stress protection. Deep ocean bacterial isolates show enhanced DMSP production under increased hydrostatic pressure. Furthermore, bacterial dsyB mutants are less tolerant of deep ocean pressures than wild-type strains. Thus, we propose a physiological function for DMSP in hydrostatic pressure protection, and that bacteria are key DMSP producers in deep seawater and sediment., Dimethylsulfoniopropionate (DMSP) is an osmolyte produced by marine microbes that plays an important role in nutrient cycling and atmospheric chemistry. Here the authors go to the Mariana Trench—the deepest point in the ocean—and find bacteria are key DMSP producers, and that DMSP has a role in protection against high pressure.

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.

Seasonal and spatial distributions of dissolved and particulate dimethylsulfoxide (DMSOd, DMSOp) were measured in the East China Sea and the Yellow Sea during March–April 2011 and October–November 2011. The concentrations of DMSOd and DMSOp in the surface water were 20.6 (5.13–73.8) and 8.90 (3.75–29.6) nmol/L in spring, and 13.4 (4.17–42.7) and 8.18 (3.44–22.6) nmol/L in autumn, respectively. Both DMSOd and DMSOp concentrations revealed similar seasonal changes with higher values occurring in spring, mainly because of the higher phytoplankton biomass observed in spring. Moreover, the ratios of DMSOp/chlorophyll a also exhibited an apparent seasonal change with higher values in autumn (35.7 mmol/g) and lower values in spring (23.4 mmol/g), thereby corresponding with the seasonal variation in the proportion of DMSO producers in the phytoplankton community between spring and autumn. In addition, DMSOd and DMSOp concentrations in the surface seawater revealed obvious diurnal variations with the maxima appearing in the afternoon.

In this paper, the kinetics and thermodynamics of Adenosine 5'-monophosphate (AMP) sorption on the sediments obtained from the Yangtze River Estuary and adjacent areas were studied, in combination with the effects of the sediments' properties and media conditions. The kinetics curves could be described by a two-compartment first-order equation, and the equilibrium isotherms fitted well with the modified Langmuir and Freundlich models. The analysis of organic phosphorus (OP) fractions changes after sorption indicated that the contents of exchangeable or loosely sorbed P

To explore the spatial and temporal distributions of dissolved organic matter (DOM) affected by Ulva prolifera bloom and the regulation of DOM released by the addition of nitrate (NO

This paper proposes a new method for the simultaneous determination of emerging contaminants (ECS) in the marine environment by solid-phase extraction (SPE)-gas chromatography-mass spectrometry (GC-MS). Organic corrosion inhibitors (OCI) and UV absorbers are common products in plastic rubber and personal care products, and they have been acknowledged as emerging contaminants due to their toxicity and bio-accumulative effects in the environment. In addition to common persistent organic pollutants (POPs), it is also necessary to detect and analyze the concentration and composition of these emerging organic contaminants in the ocean. Solid-phase extraction (SPE) and solid-phase microextraction (SPME) were used as two common pretreatment methods. After comparing their recoveries, SPE was used for treatment, and the conditions such as SPE cartridge, extraction solvent, extraction time, pH and elution solvent were optimized. The method was applied to determine the concentrations of these contaminants in seawater and sediments from the Yangtze River Estuary and its adjacent areas with a precision of about 10% and recoveries in the range of 67.40%-102.3% and 77.35%-101.8%, respectively. The detection limits of this method for the determination of contaminants in seawater and sediment were 0.03-0.47 ng/g and 0.01-0.58 ng/g. The method is simple to operate and has high precision, and can be applied to the detection of emerging pollutant concentrations in marine environments.

Nitric oxide (NO) is a non-traditional regulator of the growth of plants and phytoplankton. Here, the growth of five marine phytoplankton species, Platymonas helgolandica var. tsingtaoensis, Platymonas subcordiformis, Skeletonema costatum, Gymnodinium sp., and Prorocentrum donghaiense, was monitored, and carbonate system parameters in the culture media were determined after adding different concentrations of NO and sodium nitroprusside (SNP, NO donor) solutions. The two dietary algae (P. helgolandica var. tsingtaoensis and P. subcordiformis) and three red tide algae (S. costatum, Gymnodinium sp., and P. donghaiense) showed different responses to the same NO concentration. The red tide algae were more sensitive to exogenous NO than the dietary algae. NO with a concentration of 1.4 × 10−6 mol L−1 had the optimal stimulatory effect on the growth of the microalgae and increased the cell density by 9.8–38.3%. SNP solution with a concentration of 100 μmol L−1 inhibited the growth of the two dietary algae, and the cell density decreased by 38.8–84.3%. The addition of 10 μmol L−1 SNP solution to the three red tide algae decreased the cell density by 95.3–99.9%. Low concentrations of SNP (0.1 μmol L−1 for the two dietary algae and 0.01 μmol L−1 for the red tide algae) slightly promoted the growth of microalgae. High concentrations of NO (100 μmol L−1 SNP) inhibited CO2 assimilation, whereas low concentrations of NO (0.01–1.0 μmol L−1 SNP) promoted CO2 assimilation, indicating that NO participates in the regulation of photosynthesis.

The oceanic production and release of volatile halocarbons (VHCs) to the atmosphere play a vital role in regulating the global climate. In this study, seasonal and spatial variations in VHCs, including trichlorofluoromethane (CFC-11), methyl iodide (CH

The effects of ocean acidification and solar radiation on marine organisms have received increasing attention. Coccolithophores are a major producer of dimethylsulfoniopropionate (DMSP), which is a precursor of dimethylsulfide (DMS), a volatile biogenic active gas related to climate. Here, we investigated the individual and combined effects of elevated CO

Solid-phase speciation and porewater chemistry measured by the diffusive gradients in thin films (DGT) technique were used to understand the diagenesis of sulfur (S), iron (Fe), and phosphorus (P) in sediments of Jiaozhou Bay (China), which has been impacted by multiple anthropogenic perturbations. Despite water eutrophication, sediments of the bay are low in organic carbon and sulfide, but high in unsulfidized Fe(II). Dissimilatory iron reduction (DIR) prevails in sediments of the bay, and there is no evidence for responses of S and Fe diagenesis to the water eutrophication, which is largely attributable to unique depositional and diagenetic regimes in association with multiple anthropogenic perturbations. Good coupling of porewater Fe2+ and P in the porewaters suggests that P mobilization is driven mainly by DIR. Low Fe2+/P ratios in porewaters imply that oxidative regeneration of Fe oxides within the upper sediments is incapable of efficiently scavenging upward diffusing P.