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Volatile sulfur compounds, such as dimethyl sulfide (DMS), carbonyl sulfide (OCS), and carbon disulfide (CS 2 ), significantly influence atmospheric chemistry and climate change. Despite the oceans being an important source of these sulfides, the limited understanding of their biogeochemical cycles in seawater introduces considerable uncertainties in quantifying their oceanic emissions and assessing atmospheric OCS budgets. To address this issue, we conducted a comprehensive field survey in the tropical eastern Indian Ocean (EIO) to examine the spatial distributions, source-sink dynamics, and sea-air exchange fluxes of marine DMS, OCS, and CS 2 . Our study indicates that nutrients, organic matter, and freshwater input from terrestrial runoff significantly affect most of the source-sink processes of these sulfides in the Bay of Bengal and even the tropical EIO. The resulting sulfide accumulation in seawater combined with high wind speeds establishes the tropical EIO as a considerable direct and indirect atmospheric OCS source. These insights underscore the potentially critical role of marine environments influenced by runoff in contributing to the atmospheric OCS budget. However, by integrating these results with previous field surveys, we believe that actual OCS emissions from tropical oceans exceed some bottom-up box-model simulations, yet fall significantly below those predicted by top-down models, still insufficient to bridge the atmospheric OCS source gap. Our detailed examination of source-sink dynamics offers deeper insights into the marine sulfur cycle and has potential implications for refining future box-models, thus mitigating uncertainties in estimating marine sulfur emissions., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Benzothiazoles (BTHs), benzotriazoles (BTRs), and benzotriazole ultraviolet absorbers (BUVs) have garnered significant attention owing to their persistent nature in the environment and adverse impacts on aquatic organisms. However, there remains a dearth of investigations and studies conducted in tropical marine environments. In this study, we undertook the inaugural distributional survey and ecotoxicological relevance of BTHs, BTRs, and BUVs in seawater and sediments of the western South China Sea (WSCS). Elevated concentrations of BTHs, BTRs, and BUVs in the seawater and suspended particulate matter (SPM) were primarily observed in the Pearl River Estuary (PRE) and the western region of the WSCS, attributed to terrestrial runoff and hydrodynamic processes. Moreover, the transport of these compounds at the seawater-SPM interface was influenced by both the intrinsic properties of the contaminants and temperature variations. Spatially, concentrations of BTHs, BTRs, and BUVs in surface sediments exhibited a diminishing trend with increasing distance from the coast to offshore areas, reflecting notable anthropogenic impacts. Concentration profiles of these compounds in sediment cores displayed a bottom-up increasing trend, with total organic carbon (TOC) identified as the primary determinant governing their accumulation within sediment cores in the WSCS. Terrestrial runoff inputs and atmospheric deposition as major contributors to the occurrence of BTHs, BTRs, and BUVs in the WSCS. Simultaneously, the study underscores the non-negligible moderate mixture risk quotient associated with BTHs, BTRs, and BUVs in the sediments., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

The Ulva prolifera bloom is considered one of the most serious ecological disasters in the Yellow Sea in the past decade, forming a carbon sink in its source area within a short period but becoming a carbon source at its destination. To explore the effects of different environmental changes on seawater dissolved carbon pools faced by living U. prolifera in its originating area, U. prolifera were cultured in three sets with different light intensity (54, 108, and 162 μmol m -2  s -1 ), temperature (12, 20, and 28 °C) and nitrate concentration gradients (25, 50, and 100 μmol L -1 ). The results showed that moderate light (108 μmol m -2  s -1 ), temperature (20 °C), and continuous addition of exogenous nitrate significantly enhanced the absorption of dissolved inorganic carbon (DIC) in seawater by U. prolifera and most promoted its growth. Under the most suitable environment, the changes in the seawater carbonate system were mainly dominated by biological production and denitrification, with less influence from aerobic respiration. Facing different environmental changes, U. prolifera continuously changed its carbon fixation mode according to tissue δ 13 C results, with the changes in the concentrations of various components of DIC in seawater, especially the fluctuation of HCO 3 - and CO 2 concentrations. Enhanced light intensity of 108 μmol m -2  s -1 could shift the carbon fixation pathway of U. prolifera towards the C 4 pathway compared to temperature and nitrate stimulation. Environmental conditions at the origin determined the amount of dissolved carbon fixed by U. prolifera. Therefore, more attention should be paid to the changes in marine environmental conditions at the origin of U. prolifera, providing a basis for scientific management of U. prolifera., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

The carbonate chemistry in river-dominated marginal seas is highly heterogeneous, and there is ongoing debate regarding the definition of atmospheric CO 2 source or sink. On this basis, we investigated the carbonate chemistry and air-sea CO 2 fluxes in a hotspot estuarine area: the Changjiang Estuary during winter and summer. The spatial characteristics of the carbonate system were influenced by water mixing of three end-members in winter, including the Changjiang freshwater with low total alkalinity (TA) concentration, the less saline Yellow Sea Surface Water with high TA, and the saline East China Sea (ECS) offshore water with moderate TA. While in summer with increased river discharge, the carbonate system was regulated by simplified two end-member mixing between the Changjiang freshwater and the ECS offshore water. By performing the end-member mixing model on DIC variations in the river plume region, significant biological addition of DIC was found in winter with an estimation of -120 ± 113 μmol kg -1 caused by wintertime organic matter remineralization from terrestrial source. While this biological addition of DIC shifted to DIC removal due to biological production in summer supported by the increased nutrient loading from Changjiang River. The pCO 2 dynamics in the river plume and the ECS offshore were both subjected to physical mixing of freshwater and seawater, whether in winter and summer. In the inner estuary without horizontal mixing, the pCO 2 dynamics were mainly influenced by biological uptake in winter and temperature in summer. The inner estuary, the river plume, and the ECS offshore were sources of atmospheric CO 2 , with their contributions varying seasonally. The Changjiang runoff enhanced the inner estuary's role as a CO 2 source in summer, while intensive biological uptake reduced the river plume's contribution., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Marine distribution of dimethylsulfoniopropionate (DMSP) and its cleavage product dimethyl sulfide (DMS) is greatly affected by the community structures of bacteria, phytoplankton, and zooplankton. Spatial distributions of dissolved and particulate DMSP (DMSP d,p ), and DMS were measured and their relationships with DMSP lyase activity (DLA), abundance of DMSP-consuming bacteria (DCB), and the community structures of phytoplankton, zooplankton, and bacteria were determined during summer in the South China Sea (SCS). The depth distributions of DMSP d,p exhibited a similar trend with Chl a, reaching their maxima in the mixing layer. The DMS concentration was positively correlated with DCB abundance and DLA, indicating that DCB and DMSP lyase had a significant effect on DMS production. High DMS concentrations in the horizontal distribution coincided with high DCB abundance and DLA and may be due to the rapid growth of phytoplankton resulting from the high dissolved inorganic nitrogen concentration brought by the cold vortices. Moreover, the highest copepod abundance at station G3 coincided with the highest DMS concentrations there among stations B4, F2, and G3. These results suggest that copepod may play an important role in DMS production. The bacterial SAR11 clade was positively correlated with DLA, indicating its significant contribution to DMSP degradation in the SCS. These findings contribute to the understanding of the effect of the community assemblage on DMSP/DMS distributions in the SCS dominated by mesoscale vortices., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

An integrated observation of NO x that included coastal cities and oceanic cruises covering the Qingdao coastal waters sites (QDCW) and the Yellow Sea and East China Sea sites (YECS) was conducted in spring. The average concentrations of the coastal cities, the QDCW, and the YECS were 5.4 ± 4.1, 4.2 ± 3.5, and 2.9 ± 6.8 ppb for NO while 18.5 ± 7.2, 9.4 ± 5.2, and 4.9 ± 6.4 ppb for NO 2 , depicting lowest levels in the open seas. Atmospheric NO and NO 2 showed similar spatial variations over the seas, the stations where the air masses originated from land or nearshore regions showed higher levels, but the decisive influencing factors were not the same in the different study areas. The calculated NO x flux value in the YECS (-8.7 × 10 -17  mol N cm -2 ) indicated that the sea surface was a net sink of atmospheric NO x ., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Methane is supersaturated in surface seawater and shallow coastal waters dominate global ocean methane emissions to the atmosphere. Aerobic methane oxidation (MOx) can reduce atmospheric evasion, but the magnitude and control of MOx remain poorly understood. Here we investigate methane sources and fates in the East China Sea and map global MOx rates in shallow waters by training machine-learning models. We show methane is produced during methylphosphonate decomposition under phosphate-limiting conditions and sedimentary release is also source of methane. High MOx rates observed in these productive coastal waters are correlated with methanotrophic activity and biomass. By merging the measured MOx rates with methane concentrations and other variables from a global database, we predict MOx rates and estimate that half of methane, amounting to 1.8 ± 2.7 Tg, is consumed annually in near-shore waters (<50 m), suggesting that aerobic methanotrophy is an important sink that significantly constrains global methane emissions., (© 2022. The Author(s).)

In this study, two bacterial strains designated F2608 T and F1192 T , isolated from marine sediment sampled in Weihai, PR China, were characterized using a polyphasic approach. Strains were aerobic, Gram-stain-negative and motile. According to the results of phylogenetic analyses based on their 16S rRNA genes, these two strains should be classified under the genus Psychrobacter and they both show <98.5% sequence similarity to their closest relative, Psychrobacter celer JCM 12601 T . Moreover, strain F2608 T showed 97.5% sequence similarity to strain F1192 T . Strain F2608 T grew at 4-37 °C (optimum, 30-33 °C) and at pH 6.0-9.0 (optimum, pH 6.5-7.0) in the presence of 0-12% (w/v) NaCl (optimum, 4.0-5.0%). Strain F1192 T grew at 4-37 °C (optimum, 30 °C) and at pH 5.5-9.0 (optimum, pH 7.0-7.5) in the presence of 0.5-12% (w/v) NaCl (optimum, 3.0-4.0%). The genomic DNA G+C contents of strain F2608 T and strain F1192 T were 47.4 and 44.9 %, respectively. Genomic characteristics including average nucleotide identity and digital DNA-DNA hybridization values clearly separated strain F2608 T from strain F1192 T . The sole isoprenoid quinone in these two strains was ubiquinone 8 and the major cellular fatty acids (>10.0%) were C 18:1 ω 9 c and C 17:1 ω 8c. The major polar lipids of these two strains were phosphatidylglycerol, phosphatidylethanolamine and diphosphatidylglycerol. Based on the results of polyphasic analysis, the two strains represent two novel species of the genus Psychrobacter , for which the names Psychrobacter halodurans sp. nov. and Psychrobacter coccoides sp. nov. are proposed. The type strains are F2608 T (=MCCC 1K05774 T =KCTC 82766 T ) and F1192 T (=MCCC 1K05775 T =KCTC 82765 T ), respectively.

Dimethylated sulfur compounds play an important role in global sulfur cycle. We investigated the seasonality of dimethylsulfoniopropionate (DMSP), dimethylsulfoxide (DMSO), dimethylsulfide (DMS) and associated processes in two north China marginal seas during 2014 and 2016. High concentrations of DMS, DMSP and DMSO occurred in summer/spring, while the lowest were observed in winter. This clear seasonality was primarily driven by biomass abundance and phytoplankton communities, reflected in chlorophyll a concentrations and the composition/ratios of diatoms and dinoflagellates. The spring maximum was attributed to the annual occurrence of algal bloom. The sea-to-air fluxes of DMS also varied largely between seasons, with an average of 8.84, 11.87, 10.50 and 2.14 μmol m -2  day -1 in spring, summer, autumn and winter, respectively. Given the seasonal uncertainty of sea-to-air flux, the seasonality or situations where specific blooms occur regularly should be considered for accurate estimation of annual global DMS emission., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

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., (© 2020 Society for Applied Microbiology and John Wiley & Sons Ltd.)

In this study, components, concentrations, distribution characteristics and sources of low molecular weight organic acids (LMWOAs) in seawater of the Changjiang Estuary and its adjacent East China Sea were investigated in March 2015. Lactic, acetic and formic acids were identified with their concentration range of 0-16.7, 0-42.7 and 0-6.7 μmol·L -1 , respectively. In the surface seawater, high concentrations of LMWOAs appeared in the sea area close to the estuary and along the coast. LMWOAs were important fractions of dissolved organic carbon and acetic acid was dominant component of LMWOAs. Riverine, terrestrial input, phytoplankton and sediment release were important sources for the LMWOAs, and human activities were considered as dominant sources for them in sampling period. The consistency of regions with high concentrations of LMWOAs, eutrophication, seasonal hypoxia and frequent red tide occurrence suggested LMWOAs as potential indicators for evaluating pollution status in coastal areas., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

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.

Microbial production and catabolism of dimethylsulfoniopropionate (DMSP), generating the climatically active gases dimethyl sulfide (DMS) and methanethiol (MeSH), have key roles in global carbon and sulfur cycling, chemotaxis, and atmospheric chemistry. Microorganisms in the sea surface microlayer (SML), the interface between seawater and atmosphere, likely play an important role in the generation of DMS and MeSH and their exchange to the atmosphere, but little is known about these SML microorganisms. Here, we investigated the differences between bacterial community structure and the distribution and transcription profiles of the key bacterial DMSP synthesis (dsyB and mmtN) and catabolic (dmdA and dddP) genes in East China Sea SML and subsurface seawater (SSW) samples. Per equivalent volume, bacteria were far more abundant (~ 7.5-fold) in SML than SSW, as were those genera predicted to produce DMSP. Indeed, dsyB (~ 7-fold) and mmtN (~ 4-fold), robust reporters for bacterial DMSP production, were also far more abundant in SML than SSW. In addition, the SML had higher dsyB transcripts (~ 3-fold) than SSW samples, which may contribute to the significantly higher DMSP level observed in SML compared with SSW. Furthermore, the abundance of bacteria with dmdA and their transcription were higher in SML than SSW samples. Bacteria with dddP and transcripts were also prominent, but less than dmdA and presented at similar levels in both layers. These data indicate that the SML might be an important hotspot for bacterial DMSP production as well as generating the climatically active gases DMS and MeSH, a portion of which are likely transferred to the atmosphere.

Spatiotemporal distributions of volatile halogenated organic compounds (VHOCs) were investigated in the marine boundary air and surface seawater of the Changjiang (Yangtze River) estuary and its adjacent East China Sea in two cruises from March 11, 2015 to March 21, 2015 and from July 9, 2015 to July 20, 2015. Results revealed that the concentrations of released chlorofluorocarbons (CFCs) such as CFC-12, CFC-11, and CFC-114 in China decreased, suggesting that limitations set by the Chinese government on CFCs production and consumption have taken effect. Atmospheric concentrations of CFCs were affected by local industrial sources of emission and transport of terrestrial pollutants from coastal areas to varying degrees. Seasonal variations in atmospheric VHOCs were probably due to seasonal differences in prevalent monsoon and biogenic production. In the study periods, the investigated area was an essential source of atmospheric CH 3 Br and CH 3 I but was a net sink of CFC-12, CFC-11, and CH 3 Cl., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

A total of 133 seawater samples and 17 sediment samples were collected from 81 sampling sites in the Changjiang River Estuary and its adjacent area and were analyzed for 16 phthalate esters (PAEs). The Σ 16 PAE concentrations in the seawater and sediment samples ranged from 180.3ng·L -1 to 3421ng·L -1 and from 0.48μg·g -1 to 29.94μg·g -1 dry weight (dw), respectively, with mean values of 943.6ng·L -1 and 12.88μg·g -1 . The distribution of ∑ 16 PAE concentrations in the water column showed that PAE concentrations in the bottom samples were higher than those in the surface samples (except the transect C located inside the Changjiang River Estuary), with the maxima appearing in the bottom layer at the offshore stations. Among the 16 PAEs, di (2-ethylhexyl) phthalate (DEHP), diisobutyl phthalate (DiBP), and dibutyl phthalate (DnBP) dominated the PAEs, with 25.1%, 21.1%, and 18.9% of the Σ 16 PAEs in seawater, respectively. The comparison of ∑ 16 PAEs and salinities in transects C and A6 suggested that the Changjiang River runoff was an important driving factor influencing the distribution of PAEs. DEHP concentrations in water samples and DEHP and DnBP concentrations in sediment samples exceeded the environmental risk levels (ERL), indicating their potential hazard to the ocean environment., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Spatial distribution and sea-to-air flux of isoprene in the East China Sea and the South Yellow Sea in July 2013 were investigated. This study is the first to report the concentrations of isoprene in the China marginal seas. Isoprene concentrations in the surface seawater during summer ranged from 32.46 to 173.5 pM, with an average of 83.62 ± 29.22 pM. Distribution of isoprene in the study area was influenced by the diluted water from the Yangtze River, which stimulated higher in-situ phytoplankton production of isoprene rather than direct freshwater input. Variations in isoprene concentrations were found to be diurnal, with high values observed during daytime. A significant correlation was observed between isoprene and chlorophyll a in the study area. Relatively higher isoprene concentrations were recorded at stations where the phytoplankton biomass was dominated by Chaetoceros, Skeletonema, Pennate-nitzschia, and Thalassiosira. Positive correlation was observed between isoprene and methyl iodide. In addition, sea-to-air fluxes of isoprene approximately ranged from 22.17 nmol m -2  d -1 -537.2 nmol m -2  d -1 , with an average of 161.5 ± 133.3 nmol m -2  d -1 . These results indicate that the coastal and shelf areas may be important sources of atmospheric isoprene., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Dimethylsulfoniopropionate (DMSP) is one of the Earth's most abundant organosulfur molecules, a signalling molecule 1 , a key nutrient for marine microorganisms 2,3 and the major precursor for gaseous dimethyl sulfide (DMS). DMS, another infochemical in signalling pathways 4 , is important in global sulfur cycling 2 and affects the Earth's albedo, and potentially climate, via sulfate aerosol and cloud condensation nuclei production 5,6 . It was thought that only eukaryotes produce significant amounts of DMSP 7-9 , but here we demonstrate that many marine heterotrophic bacteria also produce DMSP, probably using the same methionine (Met) transamination pathway as macroalgae and phytoplankton 10 . We identify the first DMSP synthesis gene in any organism, dsyB, which encodes the key methyltransferase enzyme of this pathway and is a reliable reporter for bacterial DMSP synthesis in marine Alphaproteobacteria. DMSP production and dsyB transcription are upregulated by increased salinity, nitrogen limitation and lower temperatures in our model DMSP-producing bacterium Labrenzia aggregata LZB033. With significant numbers of dsyB homologues in marine metagenomes, we propose that bacteria probably make a significant contribution to oceanic DMSP production. Furthermore, because DMSP production is not solely associated with obligate phototrophs, the process need not be confined to the photic zones of marine environments and, as such, may have been underestimated.

Dimethylsulfide (DMS), dimethylsulfoniopropionate (DMSP) and dimethylsulfoxide (DMSO) are the most important biogenic organic dimethylated sulfur compounds in the ocean. The spatial distributions of these three sulfur compounds and their influencing factors were investigated in the East China Sea in June 2013. The mean concentrations of DMS, DMSPd, DMSPp, DMSOd and DMSOp in the surface seawater were 4.70, 7.00, 27.83, 13.66 and 10.78 nmol x L(-1), respectively. The horizontal distributions of DMS, DMSP and DMSO exhibited the similar patterns to that of chlorophyll a (Chl-a), with high values in coastal regions and low values in the open sea. DMS, DMSPd and DMSOp concentrations were significantly correlated with the levels of Chl-a, indicating that phytoplankton biomass might play an important role in controlling the concentrations of these sulfur compounds in the East China Sea. Moreover, positive relationships were observed between DMS and DMSPd and between DMSOd and DMS in the study area, which implied that the microbial degradation of DMSPd was the main source of DMS and DMSOd came mostly from the oxidation of DMS. The sea-to-air flux of DMS from the East China Sea in summer ranged from 0.62 to 33.98 micromol x (m2 x d)(-1), with an average of 9.71 micromol x (m2 x d)(-1).

Carbon monoxide (CO) concentration distribution, sea-to-air flux and microbial consumption rate constant, along with atmospheric CO mixing ratio, were measured in the East China Sea and the South Yellow Sea in summer. Atmospheric CO mixing ratios varied from 68 x 10(-9) -448 x 10(-9), with an average of 117 x 10(-9) (SD = 68 x 10(-9), n = 36). Overall, the concentrations of atmospheric CO displayed a decreasing trend from the coastal stations to the offshore stations. The surface water CO concentrations in the investigated area ranged from 0.23-7.10 nmol x L(-1), with an average of 2.49 nmol x L(-1) (SD = 2.11, n = 36). The surface water CO concentrations were significantly affected by sunlight. Vertical profiles showed that CO concentrations rapidly declined with depth, with the maximum values appearing in the surface water. CO concentrations exhibited obvious diurnal variations in the study area, with the maximum values being 6-40 folds higher than the minimum values. Minimal concentrations of CO all occurred before dawn. However, the maximal concentrations of CO occurred at noon. Marked diurnal variation in the concentrations of CO in the water column indicated that CO was produced primarily by photochemistry. The surface CO concentrations were oversaturated relative to the atmospheric concentrations and the saturation factors ranged from 1.99-99.18, with an average of 29.36 (SD = 24.42, n = 29). The East China Sea and the South Yellow Sea was a net source of atmospheric CO. The sea-to-air fluxes of CO in the East China Sea and the South Yellow Sea ranged 0.37-44.84 μmol x (m2 x d)(-1), with an average of 12.73 μmol x (m2 x d)(-1) (SD = 11.40, n = 29). In the incubation experiments, CO concentrations decreased exponentially with incubation time and the processes conformed to the first order reaction characteristics. The microbial CO consumption rate constants (K(co)) in the surface water ranged from 0.12 to 1.45 h(-1), with an average of 0.47 h(-1) (SD = 0.55, n = 5). A negative correlation between K(co) and salinity was observed in the present study.

The concentrations of dimethylsulfide (DMS) and dimethylsulfoniopropionate (DMSP) were measured in situ in the East China Sea and the Southern Yellow Sea during December 2011 and January 2012 to study their horizontal distributions and influencing factors. Besides, the size distribution of DMSPp and the sea-to-air flux of DMS were also investigated. The concentrations of DMS, dissolved DMSP (DMSPd) and particulate DMSP (DMSPp) ranged from 0.58 to 4.14, from 0.37 to 7.86 and from 4.29 to 25.76 nmol x L(-1), respectively, with the average values of (2.20 +/- 0.82), (2.12 +/- 1.66) and (11.98 +/- 6.23) nmol x L(-1). In addition, significantly positive correlations were found between DMS, DMSPp and chlorophyll a, and their diel variations followed the same trend, implying that phytoplankton biomass might play an important role in controlling the production and distributions of DMS and DMSP. A negative correlation was found between DMSPd and total bacterial abundance, probably because DMSPd was transferred into DMS under the action of DMSP lyase released from bacteria. Moreover, the larger nanophytoplankton (5-20 microm) contributed to the vast majority of Chl-a and DMSPp in the study area. The sea-to-air fluxes of DMS during the investigation were estimated to be from 0.61 to 25.52 micromol x (m2 x d)(-1), with an average of (8.30 +/- 5.92) micromol x (m2 x d)(-1).

Series of laboratory incubation experiments were conducted to simulate degradation of organic matter in sediment-seawater interface in hypoxia enviroments along China coastal area. Under four different redox conditions (oxygen saturation: 100%, 50%, 25% and 0%), degradations of seveal biomarkers originated from Skeletonema costatum, a typical red tide alage along China coastal area were tracked. By analyzing concentrations of four fatty acid biomarkers [14:0, 16:0, 16:1(7) and 20:5] obtained at various sampling time, results showed that their concentrations decreased significantly after 2-3 weeks' incubation. Then, their concentrations changed very slowly or very little. However, degradation of the four fatty acids varied dramatically in different incubation systems. Fatty acids 14:0, 16:1(7) and 20:5 were degraded completely in all incubation systems after two-month incubation, but 25% to 35% of 16:0 was reserved in the systems. Based on multi-G model, degradations of the four fatty acids were quantively described. The results indicated that all four fatty acids had fast-degraded and slow-degraded fractions. Their degradation rate constants (k(av)) ranged from 0.079 to 0.84 d(-1). The fastest degradation of 14:0 and 16:1 (7) occurred under 25% oxygen concentrations. For these two compounds, in the fastest degradation system, their k(av), values were 2.3 folds and 1.7 folds higher than those in the slowest degradation system [50% oxygen saturation for 14:0 and 100% oxygen saturation for 16:1(7)] respectively. The 16:0 was degraded fastest under the anoxic condition and slowest under the 50% oxygen saturation. The ratio of the two k(av)s was 2.1. The k(av)s of 20:5 had a positive relationship with oxygen saturations. Results of this study suggested that besides oxgen saturations, structure and features of organic compounds, roles of microbe in the envrioments and etc. might affect degradations of fatty acids in S. costatum in hypoxia sediment-seawater interface along China coastal area.

The horizontal distributional characteristics of nutrients (DIN, PO4(3-) -P, SiO3(2-) -Si) were studied in the sea-surface microlayer (SML) and subsurface water of the Bohai and Yellow Sea in June 2011, and the vertical distributions of nutrients in the transects of the Yellow Sea Cold Water Mass and the north of the Changjiang River estuary were also investigated. The results showed that the nutrient concentrations in the sea-surface microlayer and subsurface water decreased gradually from inshore to offshore, and higher values were observed in the Changjiang River estuary. A tongue-shaped distribution was observed in the south of the Yellow Sea as a result of the Changjiang diluted water. Stratification occurred in the surface layer and vertical mixing characteristics were observed in the bottom due to the influence of the Yellow Sea Cold Water Mass. In the vertical distributions, higher concentrations of DIN and SiO3(2-) -Si in the north of the Changjiang River estuary occurred in the sea surface compared with the bottom due to the Changjiang River diluted water. The enrichment results of NH(+) -N, NO2(-) -N, NO3(-)-N, PO4(3-) -P, SiO3(2-)-Si and DIN showed that the sea-surface microlayer displayed an apparent enrichment for nutrients except NO3(-) -N, and the mean enrichment factors ranged from 1.37 to 2.21.

Volatile halocarbons (VHCs) are important greenhouse gases, which play significant roles in the global warming and the chemistry of the atmosphere. The concentrations of four kinds of volatile halocarbons including CHCl3, C2 HCl3, C2 Cl4 and CHBr3 in seawater were determined by Purge and Trap-Chromatography in the East China Sea during the period of 23 December 2009-5 January 2010, and the sources of the VHCs were studied. The result showed that the means (ranges) of the CHCl3, C2 HCl3, C2 Cl4 and CHBr3 concentrations in the surface waters were 23.04 (6.04-107.81), 18.81 (10.67-32.35), 3.72 (0.39-9.77) and 24.33 (13.44-33.01) pmol x L(-1), respectively. The concentrations of VHCs near shore were higher than those in the open sea. In the PN section the vertical distribution of VHCs had a common feature that the maxima appeared in the upper mixed layer. The distributions of the four kinds of VHCs were significantly influenced by the Yangtze River effluent, the Kuroshio water and biological activities. A marked positive correlation between the C2 HCl3 and C2Cl4 concentrations was observed in the surface waters, suggesting that they might have some common sources. Besides, a positive correlation was found between chlorophyll a (Chl-a) and CHBr3 concentrations in the surface seawater, indicating that phytoplankton biomass might play an important role in the distribution of CHBr3 in the study area. Our data indicated that the entire ECS shelf acted as a source for atmospheric CHCl3, C2 HCl3 and CHBr3 during the study period.

The horizontal distributions and diurnal variations of particulate and dissolved dimethylsulfoxide (DMSOp, DMSOd) were studied in the surface water of the Yellow Sea and the Bohai Sea in June, 2011. The determination of DMSO was based on the DMS produced by NaBH4 reduction, which was analyzed using the purge-and-trap technique coupled with gas chromatographic separation and flame photometric detection. The concentrations of DMSOp and DMSOd ranged from 5.43 to 18.35 nmol x L(-1) and from 4.75 to 43.80 nmol x L(-1), respectively, with average values of (11.47 +/- 0.25) nmol x L(-1) and (13.42 +/- 0.58) nmol x L(-1). The results showed that no relationship was found between DMSOp and environmental factors such as chlorophyll a (Chl-a), temperature and salinity, whereas a positive correlation was observed between DMSOp/Chl-a and salinity, indicating that intracellular DMSO could act as a cryo-osmoregulator. A significant relationship was also found between DMSOd and dimethylsulfide (DMS), whereas there was no relationship between DMSOd and DMSOp or DMSOd and bacteria, implying that DMSOd in the surface water was produced mainly through the photochemical oxidation of DMS. In addition, both the DMSOp and DMSOd concentrations exhibited obvious diurnal variations with the higher values in the day time.

The ocean acidification caused by elevated CO2 concentration can affect the growth, physiology and ecology, and nutrient uptake of macroalgae. In this paper, the growth and nutrient (PO4(3-) and NO3(-)) uptake of three species of macroalgae [Ulva pertusa, Scytosiphon lomentaria and Corallina pilulifera (calcified algae)] at three pHs (8.2, 7.9 and 7.6) were investigated under conditions of monoculture and mixed culture. Under the condition of monoculture, the percents of increased wet weights of U. pertusa, S. lomentaria and C. pilulifera on day 10 were the highest at the pHs of 7.9, 7.6 and 8.2, respectively, when compared with those on day 0, and the relative growth rates of C. pilulifera at pH 7.6 were significantly lower than those at pH 8.2. The data of mixed culture experiments suggested that lower pH was beneficial for the growth of S. lomentaria, while higher pH was beneficial for the growth of C. pilulifera. In both monoculture and mixed culture, the PO4(3-) and NO3(-) concentrations at the three pHs decreased with the time. The PO4(3-) concentrations decreased sharply by 71.9% - 99.0% from day 0 to day 2, and then decreased smoothly. Under the conditions of monoculture, the PO4(3-) uptake rates of U. pertusa, S. lomentaria and C. pilulifera were the highest at pHs of 8.2, 8.2 and 7.6, respectively. The NO3(-) uptake rates of U. pertusa and C. pilulifera in monoculture were the highest at pHs of 8.2 and 7.6, respectively. Under the conditions of mixed culture, the PO4(3-) uptake rates of U. pertusa + S. lomentaria, U. pertusa + C. pilulifera, S. lomentaria + C. pilulifera were the highest at pHs of 7.6, 8.2 and 8.2, respectively. The NO3(-) uptake rates of U. pertusa + C. pilulifera at pH 7.6 were the highest among the three pHs. The lower growth and higher nutrient (PO4(3-) and NO3(-)) uptake rates of monoculture C. pilulifera at pH 7.6 showed that the uptake and assimilation of PO4(3-) and NO3(-) were not coupled. The species composition of algae was changed due to ocean acidification although the dominant species was not change. Therefore, the different responses of growth and nutrient uptake of macroalgae to long-term ocean acidification in natural environment might lead to the change in macroalgal community.

Distribution of nitric oxide (NO) concentrations in surface seawater of Jiaozhou Bay and adjacent waters was studied adopting the chemiluminescence method during February and March 2011. Based on the data of NO concentrations and related environmental parameters in hydrology, chemistry and biology, the distribution and controlling factors were discussed. The results showed that the range and the mean of NO concentrations in surface seawater of Jiaozhou Bay were 0.080-0.493 nmol x L(-1) and (0.292 +/- 0.146) nmol x L(-1), respectively. The concentrations of NO ranged from below detection limit to 0.435 nmol x L(-1) in adjacent waters of Jiaozhou Bay, with the mean of (0.160 +/- 0.130) nmol x L(-1). The concentrations of NO showed a gradually decreasing trend from inside to outside of Jiaozhou Bay, which was possibly due to the effect of terrestrial runoff and human activities. The NO concentration of surface seawater in Jiaozhou Bay and adjacent waters was one order of magnitude higher than that in the open sea. The concentrations of NO in the surface seawater exhibited an obvious diurnal variation. The highest concentration of NO appeared at 15:00, which was presumably due to the effect of illumination intensity. The influencing factors of NO concentration and distribution were complex, including nitrite, pH, light intensity and so on. The present study showed that Jiaozhou Bay and adjacent waters was a source of atmosphere NO in spring,and F(NO) was about 1.09 x 10(-15)mol x (cm2 x s) (-1).

The photodegradation of ofloxacin (OFLX) was investigated in distilled water, artificial seawater and natural seawater exposed to high-pressure mercury lamp and xeon lamp. The photolysis of OFLX was affected by various factors including light sources, initial concentrations, acetone and surfactants. The photoreaction rate of OFLX under high pressure mercury lamp was much faster than that under xeon lamp, conforming to the first-order kinetics behavior. Expose to the same light intensity, The photodegradation rate of OFLX was the quickest in natural seawater, followed by artificial seawater. The initial concentrations of OFLX were 2, 4 and 6 mg x L(-1), the rate constants were 0.163, 0.140 and 0.132 min(-1), respectively. The photodegradation rates of OFLX in seawater decreased along with its initial concentration. The addition of acetone could accelerate the photoreactions of OFLX, The constants of the reaction rate range from 0.084 2-0.102 min(-1). A positive correlation was found between the photosensitive efficiency and the added concentration of acetone. On the contrary, the addition of cetyl trimethyl ammonium bromide (CTAB), sodium dodecyl benzene sulfonate(SDBS) and Tween-20 (TW-20) inhibited the photodegradation of OFLX, of which concentrations were all 5 mg x L(-1). In addition, toxicity tests with Isochrysis galbana 8701 showed higher risk of intermediate products generated from photolysis of OFLX. The toxicity of products decreased along with the reaction.

The adsorption behaviors of norfloxacin (NOR) on marine sediments at different pH values and in the presence of four different surfactants were systematically investigated by a batch equilibrium method. The results indicated that Freundlich adsorption isotherms fitted the adsorption behavior of NOR on marine sediments very well at different pH values. The Freundlich constant K(F) and the equilibrium adsorption amount of NOR reduced with the increase of pH values, and the minimum appeared at pH 8.10. The results suggested that cation exchange was the main adsorption mechanism of NOR at pH 6.01, while Van der Waals' force, hydrophobic effects, electrostatic force were the major adsorption mechanism of NOR on marine sediments at pH 8.10. The adsorption process fitted well with pseudo-second-order kinetic equations with the addition of surfactants. Our study also indicated that the addition of surfactants had the significant influence on the saturated adsorption amount of adsorption of NOR. The equilibrium adsorption amount (Q(e)) of NOR exhibited the following sequence: Q(e) (Tween80) < Q(e) (Tween20)

Concentration distribution, sea-to-air flux, photoproduction of carbon monoxide (CO) in the surface seawater and atmospheric CO mixing ratio were measured in the Yellow Sea and the Bohai Sea. A headspace analysis system was used for CO measurement. The concentrations of CO in the surface seawater ranged from 0.19 to 3.57 nmol x L(-1), with an average of 1.24 nmol x L(-1) ( SD = 0.79, n = 69). Overall, the concentrations of CO displayed a decreasing trend from the coast to the offshore stations and followed diurnal variations after classifying and averaging the CO concentrations according to sampling and analysing time in the unit of one hour, with the maximum values in midnoon which was 10 folds higher than the minimum values in predawn. Atmospheric CO mixing ratios varied from 215 x 10(-9) to 850 x 10(-9), with an average of 414 x 10(-9) (SD = 140 x 10(-9), n = 69), due to obvious terrestrial input. The supersaturation factors of CO varied from 0.42-18.90, with an average of 3.61 (SD = 2.99, n = 69), indicating that the Yellow Sea and the Bohai Sea was a net source of atmospheric CO. The average sea-to-air fluxes of CO from the Yellow Sea and the Bohai Sea were estimated to be (1.22 +/- 1.70) micromol x (m2 x d)(-1) by the LM86 equation and (2.13 +/- 2.91) micromol x (m2 x d)(-1) by the W92 equation, respectively. Using SMARTS2 spectral irradiance model to estimate CO production, the photoproduction rate of CO was 54.60 micromol x (m2 x d)(-1) and the photoproduction of carbon in the Yellow Sea and the Bohai Sea was 26.95 x 10(9) g in spring. The photoproduction rate of CO was 25-50 times higher than the sea-to-air flux, suggesting that most part of CO was removed by microbial process in the surface seawater.

In the present study, the sorption behaviors of phenanthrene on marine sediments were investigated. Through the study of the adsorption kinetics and isotherms, the adsorption mechanism of phenanthrene on marine sediments was described. The results showed that the adsorption kinetics of phenanthrene on marine sediments could be described by the second-order kinetic equation. The sorption rate of phenanthrene was very rapid, and the equilibrium time was slightly longer in deionized water than in natural seawater. The adsorption isotherms of phenanthrene on all the sediments could be very well described by Freundlich equations. The adsorption capacity of phenanthrene had a significant positive correlation with the sediment organic carbon content. Some external factors that could affect adsorption behaviors of phenanthrene were also investigated. Results of the present study showed that the adsorption capacity of phenanthrene on the sediment decreased with increasing temperature. Moreover, the adsorption amounts of phenanthrene on the sediment appeared to be lower in natural seawater than in deionized water. Finally, the presence of the surfactant of Tween20 in the system could enhance the adsorption of phenanthrene on the sediment, and the adsorbance was proportional to the concentration of Tween20., (Environ. Toxicol. Chem. 2010;29:2169-2176. © 2010 SETAC.)

Spatial variations in dimethylsulfide (DMS) and dimethylsulfoniopropionate (DMSP) were surveyed in the surface microlayer and in the subsurface waters of the low productivity South China Sea in May 2005. Overall, average subsurface water concentrations of DMS and DMSP of dissolved (DMSPd) and particulate (DMSPp) fractions were 1.74 (1.00-2.50), 3.92 (2.21-6.54) and 6.06 (3.40-8.68) nM, respectively. No enrichment in DMS and DMSPp was observed in the microlayer. In contrast, the microlayer showed a DMSPd enrichment, with an average enrichment factor (EF, defined as the ratio of the microlayer concentration to subsurface water concentration) of 1.40. In the study area, none of the sulfur components were correlated with chlorophyll a. An important finding in this study was that DMS, DMSP and chlorophyll a concentrations in the surface microlayer were respectively correlated with those in the subsurface water, suggesting a close linkage between these two water bodies. The ratios of DMS:Chl-a and DMSPp:Chl-a showed a gradually increasing trend from North to South. This might be due to changes in the proportion of DMSP producers in the phytoplankton community with the increased surface seawater temperature. A clear diurnal variation in the DMS and DMSP concentrations was observed at an anchor station with the highest concentrations appearing during the day and the lowest concentrations during the night. The higher DMS and DMSP concentrations during daytime might be attributed to the light-induced increase in both algal synthesis and exudation of DMSP and biological production of DMS. The mean flux of DMS from the investigated area to the atmosphere was estimated to be 2.06 micromo lm(-2)d(-1). This low DMS emission flux, together with the low DMS surface concentrations was attributed to the low productivity in this sea.

The sorption behaviors of nitrobenzene on marine sediments were systematically investigated in this study. The nitrobenzene sorption on both HCl-treated and untreated sediments accorded well with the linear sorption isotherm. It occurred primarily through partition function of organic carbon of sediments. In comparison, the sorption behavior of nitrobenzene on H2O2-treated sediments was nonlinear and conformed to Langmuir isotherm. Sorption of nitrobenzene on H2O2-treated sediment was mainly through surface function of sediment minerals such as clays. With the increase of ionic strength (salinity), solubility of nitrobenzene in solution would decrease. At the same time, the release of dissolvable part of organic carbon into water solution would also decrease. As a result, partition coefficient and saturate adsorption amount of nitrobenzene on marine sediments increased with increasing salinity of seawater. Contrary to the influence of salinity, partition coefficient and saturate adsorption amount of nitrobenzene decreased with increasing temperature.

Dimethyl sulfide (DMS) is the predominant natural sulfur source and plays a pivotal role in regulating global climate. However, the current method for estimating seawater DMS concentrations has limitations, and the existing DMS‐induced radiative effect heavily relies on bottom‐up DMS climatologies. This study aims to improve the method for estimating seawater DMS concentrations as well as to evaluate its induced aerosol direct radiative effect (DRE) and indirect radiative effect (IRE) using a state‐of‐the‐art aerosol microphysics scheme integrated with a chemical transport model. The predicted seawater DMS concentrations based on data‐driven methods were verified with multi‐year in situ measurements, revealing a marked reduction in mean bias by over 80%. Results show that our estimates generally indicate lower seawater DMS concentrations (1.48–1.88 μmol/m3) compared to previous seawater DMS climatologies, with differences ranging from −37% to 11%, and that interannual variability in DMS concentrations is varies significantly, particularly in polar regions. The DRE and cloud‐albedo IRE induced by DMS were −0.06 and −0.19 W/m2, respectively, representing a cooling effect on radiative effect that was weaker by 31.4% and 27.0% of those derived from the commonly used bottom‐up DMS climatology. The comprehensive evaluation of the model's performance of atmospheric DMS prediction based on global‐scale observations shows a significant improvement after using our estimates. Thus, we conclude that the global DMS fluxes provided in the past are overestimated, including its resulting DMS radiative effect, which highlights the need for refining the estimation of global aerosol radiative effect to enhance the accuracy of assessing aerosol‐induced climate impacts. Plain Language Summary: Over the past decade, there has been a significant decrease in global anthropogenic sulfur emissions. This decrease sheds light on the importance of natural sulfur sources, specifically dimethyl sulfide (DMS), the largest among them, and its potential impact on climate. Several modeling studies have assessed the radiative effects induced by DMS. However, these models depend on data that combines DMS measurements from a global database, using smoothing and interpolation methods to create a map of DMS concentrations in sea surfaces. This introduces uncertainties due to the methods used. Our study aims to improve the method for estimating seawater DMS concentration and evaluate its induced radiative effect. Our study provides a more accurate and comprehensive assessment of the global distribution of DMS concentrations, leading to an enhanced understanding of the climate impact of natural sulfur sources. Our findings show that DMS concentration and its climate impact vary across regions and time, generally being lower than previous estimates. This emphasizes the need to refine the estimation of global aerosol radiative effect to enhance the precision of assessing aerosol‐induced climate impacts. This adjustment is important for the progression of global climate governance initiatives. Key Points: Global seawater Dimethyl sulfide (DMS) concentration products (1° × 1°) from 2011 to 2020 were developed based on improved top‐down methodsThis study presents lower estimates for DMS concentration compare to the prior DMS climatology, aligning more accurately with observationsComprehensive evaluation of model performance suggests previous reported DMS‐derived radiative effects are overestimated [ABSTRACT FROM AUTHOR]

The inflow of warm and nutrient‐rich Pacific Water (PW) through the Bering Strait into the Arctic Ocean is likely to have far‐reaching consequences for the ecosystem and biogenic sulfur cycle in the Earth's sensitive subarctic–arctic region of the Pacific sector, even impacting climate change under global warming scenarios. We performed a detailed biogeochemical study of summer biogenic sulfur cycling from cold (2012) to warm (2014) years in the Bering Strait and the Chukchi Sea, so as to highlight the importance of enhanced Pacific inflow in driving dimethylsulfide (DMS) variability. In the Bering Strait, the enhanced Pacific inflow led to the vertical expansion of the eastern high‐DMS regions due to the vertical extension of Alaska Coastal Water, and the horizontal expansion of the western surface high‐DMS regions due to the westward intrusion of Bering Shelf Water. The enhanced extension of PW potentially stimulated seawater warming, the northward retreat of the ice edge, and the enlargement of sea ice‐free areas in the Chukchi Sea. The northern ice melting zone at 71°N with a bloom of phytoplankton was an area of locally high dimethylsulfoniopropionate concentrations and slow DMS consumption in 2012. A hotspot for dimethylated sulfur compound concentrations and DMS sea–air flux occurred in the convergence region near 67.7°N during 2014, due to enhanced mixing caused by increased Bering Sea Water. Owing to the increased advection of PW during 2012–2014, surface DMS and its emission to the atmosphere increased sharply by threefold in the Chukchi Sea. [ABSTRACT FROM AUTHOR]

Volatile organic sulfur compounds (VSCs), including carbon disulfide (CS 2) , dimethyl sulfide (DMS), and carbonyl sulfide (COS), were surveyed in the seawater of the Bohai and Yellow seas and the overlying atmosphere during spring and summer of 2018 to understand the production and loss of VSCs and their influence factors. The concentration ranges of COS, DMS, and CS 2 in the surface seawater were 0.14–0.42, 0.41–7.74, and 0.01–0.18 nmol L -1 during spring and 0.32–0.61, 1.31–18.12, and 0.01–0.65 nmol L -1 during summer, respectively. The COS concentrations exhibited positive correlation with dissolved organic carbon (DOC) concentrations in seawater during summer, which verified the photochemical production of COS from chromophoric dissolved organic matter (CDOM). High DMS concentrations occurred near the Yellow River, Laizhou Bay, and Yangtze River estuary, coinciding with high nitrate and chlorophyll (Chl) a concentrations due to river discharge during summer. The COS, DMS, and CS 2 concentrations were the highest in the surface seawater and decreased with the depth. The mixing ratios of COS, DMS, and CS 2 in the atmosphere were 255.9–620.2, 1.3–191.2, and 5.2–698.8 pptv during spring and 394.6–850.1, 10.3–464.3, and 15.3–672.7 pptv in summer, respectively. The ratios of mean oceanic concentrations and atmospheric mixing ratios for summer to spring in COS, DMS, and CS 2 were 1.8, 3.1, 3.7 and 1.6, 4.6, 1.5, respectively. The ratios of the mean sea-to-air fluxes for summer to spring in COS, DMS, and CS 2 were 1.2, 2.1, and 4.3. The sea-to-air fluxes of VSCs indicated that the marginal seas are important sources of VSCs in the atmosphere. The results support a better understanding of the contribution of VSCs in marginal seas. [ABSTRACT FROM AUTHOR]

Environmental context: Organophosphorus (OP) is bioavailable to phytoplankton with photolysis can play an important role in the process. The photolysis behaviour of an OP (adenosine 5′-monophosphate, AMP) in seawater was investigated, and AMP can release inorganic phosphate under environmentally relevant light conditions, indicating OP photodegradation might be important in the phosphorus biogeochemical cycle. The results are helpful to further understand the bioavailability and cycle of OP in marine environment. Rationale: Organic phosphorus (OP) is a potential source of bioavailable phosphorus for phytoplankton through photolysis and other degradation processes. Therefore, OP photodegradation plays an important role in phosphorus biogeochemical cycle. Methodology: Taking adenosine 5′-monophosphate (AMP) as a model OP, we investigated the photolysis behaviour in seawater and discussed the mechanism. The photolysis dynamics were studied based on the inorganic phosphorus production at appropriate time intervals, which was analysed by spectrophotometric molybdenum blue method. The effects of medium, light and radicals were investigated. Results: It was found that AMP can release inorganic phosphate under photosynthetically active radiation and ultraviolet (UV) with UVB being the most reactive band. The degradation of AMP in seawater was lower than that in deionised water under the same conditions, and the fresh seawater was more beneficial than aged seawater. The kinetics could be described by a pseudo-first order equation. Fe3+ can promote the photolysis due to the generation of ·OH radicals, while within the range of this study, changes of Fe3+ content have no substantial effect on the promotion. The influence of ethanol and tetrahydrofuran as radical inhibitor showed evident inhabitation to the degradation, indicating that ·OH and [sup 1]O[sub 2] played an important role in the process, and ·OH seemed more important than [sup 1]O[sub 2]. Discussion: OP photodegradation is of importance in the phosphorus biogeochemical cycle. Varying properties of the medium and light can affect the OP transformation in seawater. The results are helpful to further understand the bioavailability and cycle of OP in the marine environment. [ABSTRACT FROM AUTHOR]

Methanol metabolism can play an important role in marine carbon cycling. We made contemporaneous measurements of methanol concentration and consumption rates in the northwest Pacific Ocean to constrain the pathways and dynamics of methanol cycling. Methanol was detected in relatively low concentrations (<12–391 nM), likely due to rapid biological turnover. Rates of methanol oxidation to CO2 (0.9–130.5 nmol L−1 day−1) were much higher than those of assimilation into biomass (0.09–6.8 nmol L−1 day−1), suggesting that >89.7% of methanol was utilized as an energy source. Surface water acted as a net methanol sink at most sites, with an average flux of 9 μmol L−1 day−1. Atmospheric deposition accounted for 22.7% of microbial methanol consumption in the mixed layer, illustrating that the atmosphere is less important than internal processes for driving methanol cycling in these pelagic waters. Plain Language Summary: Methanol is one of the most abundant oxygenated volatile organic compounds in the atmosphere and microbial methanol metabolism is an important part of the marine carbon cycle. However, only a limited number of studies describe methanol cycling in marine waters, and the sources and sinks of methanol remain largely unconstrained in the Pacific Ocean. We investigated the distribution and microbial consumption of methanol in the Kuroshio‐Oyashio extension region of northwest Pacific Ocean. Methanol was used primarily as an energy source and the rapid biological turnover of methanol contributed to relatively low‐standing stocks of methanol. Air‐sea flux estimates suggested that the atmosphere was a net source of methanol to the study area. Compared to in situ production and consumption rates, air‐sea exchange represented a less important process for methanol cycling in the mixed layer. Our results add to the global database of methanol concentrations and help to constrain the biological sources and sinks of methanol in the surface ocean. Key Points: Methanol was detected in relatively low concentrations due to rapid biological consumption in the Kuroshio‐Oyashio extension regionMuch higher oxidation rates than assimilation rates suggested methanol was predominantly used as an energy sourceAtmospheric deposition is a source of methanol in the mixed layer and accounted for 22.7% of microbial methanol consumption [ABSTRACT FROM AUTHOR]

Nitric oxide (NO) is a short-lived intermediate of the oceanic nitrogen cycle. However, our knowledge about its production and consumption pathways in oceanic environments is rudimentary. In order to decipher the major factors affecting NO photochemical production, we irradiated several artificial seawater samples as well as 31 natural surface seawater samples in laboratory experiments. The seawater samples were collected during a cruise to the western tropical North Pacific Ocean (WTNP, a N–S section from 36 to 2 ∘ N along 146 to 143 ∘ E with 6 and 12 stations, respectively, and a W–E section from 137 to 161 ∘ E along the Equator with 13 stations) from November 2015 to January 2016. NO photoproduction rates from dissolved nitrite in artificial seawater showed increasing trends with decreasing pH, increasing temperature, and increasing salinity. In contrast, NO photoproduction rates (average: 0.5±0.2×10-12 mol L -1 s -1) in the natural seawater samples from the WTNP did not show any correlations with pH, water temperature, salinity, or dissolved inorganic nitrite concentrations. The flux induced by NO photoproduction in the WTNP (average: 13×10-12 mol m -2 s -1) was significantly larger than the NO air–sea flux density (average: 1.8×10-12 mol m -2 s -1), indicating a further NO loss process in the surface layer. [ABSTRACT FROM AUTHOR]

The 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. Plain Language Summary: Dimethylsulfide (DMS) in the atmosphere can alter the environment and climate by its certain oxidation products. DMS emission from the ocean to the atmosphere is the most important source of atmospheric DMS. Therefore, it is of great importance to investigate the distribution, occurrence, and fate of marine DMS. In our study, the concentrations of DMS, dimethylsulfoniopropionate (DMSP, the precursor of DMS), and dimethylsulfoxide (the photooxidation or microbial oxidation product of DMS) in the marine boundary layer of the Yellow Sea and Bohai Sea were determined, and in situ deck incubation and irradiation experiments were conducted to research the cycle processes of the dimethylated sulfur compounds. We found that the concentrations of DMS and DMSP were mainly influenced by the freshwater input in the study area. The concentrations of DMS and DMSP were significantly correlated with the stocks of chlorophyll a. DMS in the surface water was primarily removed by microbial metabolism and photooxidation. In addition, the flux of DMS from the study area to the atmosphere was also estimated, suggesting it is an important net source of atmospheric DMS. Key Points: The distributions of biogenic dimethylated sulfur compounds were significantly affected by anthropogenic activity and river dischargeMicrobial consumption and photooxidation were the dominant pathways contributing to the DMS sinkBioproduction was not the sole but the primary source of DMS in the surface seawater in the Yellow Sea and Bohai Sea [ABSTRACT FROM AUTHOR]

As an important trace gas, carbon monoxide (CO) is considered to be mainly released by the ocean into the atmosphere. To further understand the role of the marginal seas for marine CO emission, we investigated sea‐to‐air flux and spatial distribution as well as biological consumption of CO using the Yellow and Bohai Seas as research objects. In the surface water, CO concentrations varied largely between 0.109 and 6.26 nmol/L. Strong vertical and diurnal variabilities were also observed, which could be attributed to the sunlight‐induced photochemical production of CO at different sampling time and depth. The atmospheric CO mixing ratios generally decreased from the coast to the open ocean, possibly due to the influence of anthropogenic activity. Relative to atmospheric CO, the concentrations of CO were mostly supersaturated in the surface water, suggesting that both the Bohai and the Yellow Seas were significant CO source in the atmosphere. Average sea‐to‐air flux of CO was about 1.76 μmol · m‐2 · day‐1, which largely depended on the saturation factor and wind speed. As an important removal pathway, microbial consumption of CO exhibited the first order kinetics. The rapid turnover of CO (3.2−9.6 hr) indicated that microbial metabolism was the major CO consumer in the surface waters that could significantly regulate the emission of CO to the atmosphere. Overall, this study improved our understanding of the biogeochemical CO cycling in marginal seas as well as in coastal regions. Key Points: Strong vertical and diurnal variabilities were observed, which could be attributed to the sunlight‐induced photochemical production of CORelative to atmospheric CO, the concentrations of CO were mostly supersaturated in the surface waterMicrobial metabolism was the major CO consumer in the surface waters that could significantly regulate the emission of CO to the atmosphere [ABSTRACT FROM AUTHOR]

Carbonyl sulfide (COS), dimethyl sulfide (DMS), and carbon disulfide (CS2) concentrations were determined in seawater and the overlying atmosphere of the Changjiang Estuary and the adjacent area during two cruises from 22 February 2016 to 15 March 2016 and from 03 July 2016 to 25 July 2016. The concentration ranges of COS, DMS, and CS2 in seawater during winter were 121–388 pmol L−1, 0.321–1.59 nmol L−1, and 10.3–46.8 pmol L−1, respectively, and those during summer were 98–346 pmol L−1, 0.397–9.13 nmol L−1, and 13.3–65.4 pmol L−1. The DMS concentration in surface seawater varied seasonally, whereas the COS and CS2 concentrations varied little. The atmospheric mixing ratios of COS, DMS, and CS2 were 459–777 pptv, 5.2–96.8 pptv, and 96.9–164 pptv during winter and 417–644 pptv, 133–365 pptv, and 15.8–89.8 pptv during summer, respectively. A correlation analysis revealed that COS concentration was related to the concentrations of DMS and CS2. The estimated fluxes of COS, DMS, and CS2 were in the range of 1.19–2.06 μg m−2 d−1, 15.11–164.81 μg m−2 d−1, and 0.27‐1.32 μg m−2 d−1 during winter and 0.61–0.97 μg m−2 d−1, 71.76–2511 μg m−2 d−1, and 0.38–1.47 μg m−2 d−1 during summer, respectively. These results indicate that the study area is a sink for COS, but served as a source of atmospheric DMS and CS2 during the study period. [ABSTRACT FROM AUTHOR]

Sulfur hexafluoride (SF 6) is a powerful greenhouse gas with a high global warming potential. While SF 6 emissions from urban areas have been extensively studied, our knowledge about SF 6 concentrations in the oceanic atmosphere and its air-sea exchange remains limited. Herein, the concentrations of SF 6 in the atmosphere and surface seawater of the WPO (Western Pacific Ocean) and EIO (Eastern Indian Ocean) were comprehensively characterized from 2019 to 2022 in the first long-term study. The mean mixing ratios of SF 6 over the WPO and EIO during 2019–2020 (2021–2022) were 10.9 (11.2) and 10.9 (11.1) ppt, respectively. The atmospheric SF 6 concentration over the WPO and EIO increased at rates of 0.40 ± 0.06 and 0.58 ± 0.28 ppt yr−1, respectively, surpassing previously reported annual growth rates. The faster growth was primarily attributed to the influence of polluted air masses originating from eastern Asian countries, particularly Japan, Northeast China, and India. This might explain why the radiative forcing caused by SF 6 in the study region was higher than the global average. The concentrations of SF 6 in the surface seawater of the WPO and EIO ranged from 0.33 to 2.54 fmol kg−1, and the distribution was affected by atmospheric concentrations and ocean currents. Estimated air-sea fluxes revealed that the ocean acted as a significant sink of atmospheric SF 6 , and the preliminary estimation suggested oceanic uptake accounts for about 7% of annual global SF 6 emissions. Based on these findings, we tentatively suggest that the strength of the ocean as a sink of SF 6 may warrant reassessment. The global oceanic uptake of SF 6 has the potential to reduce its global abundance and environmental impacts. [Display omitted] • Elevated atmospheric SF 6 levels was due to emission from East Asian countries. • Atmospheric concentration and ocean currents dictated SF 6 in the seawater. • The oceanic uptake of atmospheric SF 6 was about 7% of its emissions. [ABSTRACT FROM AUTHOR]

The spatial distribution, chemical composition and ecological risk of 16 phthalate esters (PAEs) were investigated in the sea-surface microlayer (SML), seawater and sediment samples of the Bohai Sea (BS) and the Yellow Sea (YS). The concentration levels of the ΣPAEs spanned a range of 449–13441 ng L −1 in the SML, 453–5108 ng L −1 in seawater, and 1.24–15.8 mg kg −1 in the sediment samples, respectively, with diisobutyl phthalate (DiBP), di-n-butyl phthalate (DBP) and di-ethylhexyl phthalate (DEHP) as the dominant PAEs in both the water and sediment samples. The concentrations of ΣPAEs in the BS were higher than those in the YS. The vertical distribution of ΣPAEs in the water column showed that the concentrations were higher in the surface waters, but decreased slightly with depth, and started to increase at the bottom. Additionally, PAEs were significantly enriched in the SML, with an average enrichment factor of 1.46. The ecological risk of the PAEs was evaluated by the risk quotient (RQ) method, which indicated that DEHP posed a high risk to aquatic organisms in the whole water-phase, while the RQ values of DBP and DiBP reached a high risk levels in sedimentary environment. [ABSTRACT FROM AUTHOR]