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The interplay of global climate change and anthropogenic activities has significantly affected the carbon cycle in coastal ocean environments. Consequently, further investigation into the carbonate system, carbon source and sink processes, and acidification mechanisms is essential. This study examined the surface carbonate system offshore of Qingdao, utilizing data from nine spring cruises in 2011-2019. The inter-annual variations in sea surface temperature revealed a gradual upward trend, whereas chlorophyll a (Chl-a) and apparent oxygen utilization (AOU) exhibited alternating trends of increase and decrease. Over the period from 2011 to 2019, pH levels ranged from 8.00 to 8.19, partial pressure of CO 2 (pCO 2 ) values varied between 187.8 and 364.1 μatm, and calcium carbonate saturation (Ω arag ) ranged from 3.22 to 4.79. From 2011 to 2017, both pH and Ω arag showed a decreasing trend, attributed to the increasing influence of respiration. In contrast, an upward trend was observed for both parameters during 2018 and 2019, indicating a decline in respiration's contribution. Biological processes, especially the increase in respiration caused by the nutrients and organic matter released through human activities, were pivotal in determining spatial variations in pCO 2 and Ω arag offshore, while the impact of mixing processes and temperature was comparatively negligible. Furthermore, the Ulva prolifera bloom event in July 2015 significantly affected the coastal waters of Qingdao's carbonate system when compared to the no-bloom period in March 2015. Overall, the study area functioned as a sink for atmospheric CO 2 in the spring. The fluctuations in air-sea CO 2 fluxes corresponded with changes in ΔpCO 2 and wind speeds, with surface seawater air-sea CO 2 fluxes ranging from -17.7 to 12.2 mmol m -2 d -1 between 2011 and 2019, yielding an average flux of -9.4 ± 5.3 mmol m -2 d -1 ., 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.)

Nitrogen oxides (NO x  = NO + NO 2 ) have essential impacts on global climate and the environment, making it essential to study the contribution of wetland-generated NO x to environmental problems. With exogenous nitrogen input from anthropogenic activities, wetland sediments become active emission hotspots for NO x . In this study, we conducted field experiments in a typical salt marsh wetland to measure nitric oxide (NO, the primary component of NO x from sediments) exchange fluxes in both mudflat and vegetated sediments. We found that NO fluxes in vegetated sediments (0.40 ± 0.15 × 10 -12  kg N m -2  s -1 ) were relatively higher than in mudflat sediments (-1.31 ± 1.39 × 10 -12  kg N m -2  s -1 ), with this difference occurring only during the vegetation-dying season (autumn). Correlations between sediment NO fluxes and environmental parameters revealed that NO flux variation during the observation period was primarily influenced by sediment respiration, temperature, water content, and substrate availability. However, the influence of these factors on NO fluxes differed between mudflat and vegetated sediments. In-situ data analysis also suggested that tidal horizontal migration, which affects sediment substrate and salinity, may regulate sediment NO emissions. Furthermore, in-situ incubations with nitrogen addition (ammonia, nitrite, and nitrate) were conducted to study the response of sediment NO emissions to exogenous nitrogen. We observed that nitrogen addition caused a 259.7 % increase in NO emissions from vegetated sediments compared to the control during the effective period of nitrogen addition (days 1-3). However, although nitrogen addition markedly stimulated sediment NO emissions, the overall NO production capacity constrained the extent of this increase., 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 B.V. 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.)

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.)

Understanding the control mechanisms of carbon dioxide (CO 2 ) emissions in intertidal wetland sediments is beneficial for the concern of global carbon biogeochemistry and climate change. Nevertheless, multiple controls on CO 2 emissions from intertidal wetland sediments to the atmosphere still need to be clarified. This study investigated the effect of tidal action on CO 2 emissions from salt marsh sediments covered by Spartina alterniflora in the Jiaozhou Bay wetland using the static chamber method combined with an infrared CO 2 detector. The results showed that the CO 2 emission fluxes from the sediment during ebb tides were higher than those during flood tides. The whole wetland sediment acted as a weak source of atmospheric CO 2 (average flux: 24.44 ± 16.80 mg C m -2  h -1 ) compared to terrestrial soils and was affected by the cycle of seawater inundation and exposure. The tidal influence on vertical dissolved inorganic carbon (DIC) transport in the sediment was also quantitated using a two-end member mixing model. The surface sediment layer (5-15 cm) with maximum DIC concentration during ebb tides became the one with minimum DIC concentration during flood tides, indicating the DIC transport from the surface sediment to seawater. Furthermore, aerobic respiration by microorganisms was the primary process of CO 2 production in the sediment according to 16 S rDNA sequencing analysis. This study revealed the strong impact of tidal action on CO 2 emissions from the wetland sediment and provided insights into the source-sink pattern of CO 2 and DIC at the land-ocean interface., 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 © 2023 Elsevier Inc. All rights reserved.)

To examine the sulfate assimilation and reduction process and the regulation of illumination, diatom Phaeodactylum tricornutum and dinoflagellate Amphidinium carterae were selected for continuous simulation incubation under different photon flux densities (PFDs) (54, 108 and 162 μmol photons m -2  s -1 ), and concentration variations of related sulfur compounds sulfate, dimethylsulfoniopropionate (DMSP), dimethylsulfide (DMS) and acrylic acid (AA) in the culture system were observed. The optimal PFD for the growth of two microalgae was 108 μmol photons m -2 s -1 . However, the maximum sulfate absorption occurred at 162 μmol photons m -2 s -1 for P. tricornutum and at 54 μmol photons m -2 s -1 for A. carterae. With the increase of PFD, the release of DMSP by P. tricornutum decreased while A. carterae increased. The largest release amount of DMS was 0.59 ± 0.05 fmol cells -1 for P. tricornutum and 2.61 ± 0.89 fmol cells -1 for A. carterae under their optimum growth light condition. The sulfate uptake of P. tricornutum was inhibited by the addition of amino acids, cysteine had a greater inhibitory effect than methionine, and the absorption process was controlled by light. The intermediate products of sulfur metabolism had an up-control effect on the sulfate uptake process of P. tricornutum. However, the addition of amino acids had no obvious effect on the sulfate absorption of A. carterae., 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 © 2023 Elsevier Ltd. All rights reserved.)

One new pentacyclic triterpenoid glycoside, ardisiapunine E (1), along with two known compounds were isolated from the root of Ardisia lindleyana D.Dietr. Their structures were elucidated by 1 H and 13 C NMR, DEPT, HMBC, HSQC, 1 H- 1 H COSY and NOESY spectroscopic analyses, ESI-MS, and literature. Compounds 1-3 exhibited obvious anti-proliferative activities against the HeLa cell line in a dose- and time-dependent manner by inducing G2/M phase arrest and apoptosis in vitro, both consisting of pentacyclic triterpenes and sugar. Hence, this study identified a new and two known pentacyclic triterpenoid glycosides promoting apoptosis as a potential anti-proliferative agent., 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 © 2023 Elsevier Ltd. All rights reserved.)

Background: Many studies have investigated the effects of soy isoflavones on weight control, but few have focused on the role of equol, a gut-derived metabolite of daidzein with greater bioavailability than other soy isoflavones., Objectives: This study examined the association of equol production with obesity and explored the mediating roles of equol-related gut microbiota and microbial carnitine metabolites., Methods: This 6.6-y prospective study included 2958 Chinese adults (2011 females and 947 males) aged 60.6 ± 6.0 y (mean ± SD) at baseline. Urinary equol and isoflavones were measured using HPLC-tandem MS. BMI, percentage fat mass (%FM), and serum triglycerides (TGs) were assessed every 3 y. Metagenomics sequencing and assessment of carnitine metabolites in feces were performed in a subsample of 897 participants., Results: Urinary equol, but not daidzein and genistein, was independently and inversely associated with the obesity-related indicators of BMI, %FM, and a biomarker (TGs). Equol producers (EPs) had lower odds of adiposity conditions and a reduced risk of 6.6-y obesity progression than non-EPs among total participants. Gut microbial analyses indicated that EPs had higher microbiome species richness (P = 3.42 × 10-5) and significantly different β-diversity of gut microbiota compared with the non-EP group (P = 0.001), with 20 of 162 species differing significantly. EPs (compared with non-EPs) had higher abundances of Alistipes senegalensis and Coprococcus catus but lower abundances of Ruminococcus gnavus (false discovery rate <0.05). Among the 7 determined fecal acylcarnitine metabolites, palmitoylcarnitine, oleylcarnitine 18:1, and stearylcarnitine were inversely associated with EPs but positively correlated with obesity conditions and progression. Path analyses indicated that the beneficial association between equol and obesity might be mediated by gut microbiota and decreased production of 3 acylcarnitines in feces., Conclusions: This study suggests a beneficial association between equol and obesity, mediated by the gut microbiome and acylcarnitines, in adults.This trial was registered at clinicaltrials.gov as NCT03179657., (© The Author(s) 2022. Published by Oxford University Press on behalf of the American Society for Nutrition.)

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 3 -N) nutrients, the variation in DOM was analyzed by three cruises in the coastal waters of the southern Yellow Sea (SYS) off Qingdao during a 2018 U. prolifera bloom. A mesocosm experiment was conducted during the decay of U. prolifera. The U. prolifera bloom resulted in higher concentrations of the bulk DOM except for total dissolved amino acids (TDAA), compared with levels recorded during non-bloom periods. Three different fluorescent substances of chromophoric dissolved organic matter (CDOM) were identified, which were also affected by the bloom. Concentrations of total dissolved carbohydrates (TCHO), monosaccharides (MCHO), and polysaccharides (PCHO) peaked during the late bloom, with average levels of 49.78 ± 9.73, 14.23 ± 3.32, and 35.55 ± 9.19 μmol C L -1 , respectively, accompanied by an increase of DOC, indicating release of DOM with U. prolifera decay. In contrast, the concentrations of CDOM and TDAA declined during the late bloom, with averages of 0.10 ± 0.10 m -1 and 1.16 ± 0.82 μmol L -1 , suggesting that the yields of CDOM and TDAA were regulated by the U. prolifera bloom and other mechanism. These findings were confirmed by the mesocosm experiment. DOM production was obviously improved by NO 3 -N addition except for TDAA and CDOM. The release of protein-like CDOM was primarily regulated by NO 3 -N nutrients, however, it was not obvious with humic-like CDOM. Our findings provide evidence supporting the role of U. prolifera blooms in the coastal DOM pool and its significant effect on the marine carbon cycle., 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 © 2022 Elsevier B.V. All rights reserved.)

Dissolved inorganic carbon (DIC) and its stable isotope (δ 13 C-DIC) are important parameters for studying carbon cycling in aquatic environments. Traditional methods based on isotope-ratio mass spectrometers are labor-intensive and not easily deployable at field sites. Here we report the performance of a method that simultaneously measures DIC concentration and its stable isotope by using a CO 2 extraction device and a Cavity Ring-Down Spectroscopy (CRDS) detector. A multi-port valve is used to increase sample throughput and improve precision. The instrument achieves average precisions of better than ±1.95 μmol kg -1 and ±0.06‰, respectively, for DIC and δ 13 C-DIC in seawater based on three injections for each sample. We also provide recommendations on how to precisely determine δ 13 C-DIC samples with a wide range of DIC content in different types of waters by examining injection volume and concentration effects. This technique was applied to study carbon cycling in the Delaware Estuary. It demonstrates that a simultaneous and precise determination of both DIC and δ 13 C-DIC is a powerful and effective approach for constraining the processes controlling aquatic carbon cycling and CO 2 fluxes. Both laboratory tests and field applications confirmed that this system can be used with high precision to study carbon cycling in various aquatic environments., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: W. -J. Cai is related to the Apollo SciTech., (Copyright © 2022. Published by Elsevier B.V.)

As an environmental nuisance, Ulva prolifera green tides have occurred annually in the southern Yellow Sea since 2007. While it is expected that high levels of biological activity during these blooms can alter seawater carbonate chemistry, there has been little research on the responses of marine carbonate system to green tides. Here, the effects of the bloom on the carbonate system were examined on three cruises in June, July, and September, corresponding to the early-, late-, and after-bloom periods of the U. prolifera bloom in Qingdao coastal waters in 2018. Among these three stages, the pH (National Bureau of Standards scale), dissolved inorganic carbon (DIC), total alkalinity (TA), and partial pressure of CO 2 (pCO 2 ) were all affected by bloom, with the highest pH and lowest DIC and TA concentrations of the surface seawater occurring at the late-bloom stage. While pCO 2 continuously increased from the beginning to the end of the bloom. TA increased by ∼40 μmol kg -1 between the early- and after-bloom periods likely due to the shifts in the carbonate system equilibrium caused by increased CO 3 2- concentrations and the organic matter released by U. prolifera during decomposition. Compared to nearby areas with no U. prolifera bloom, the green tide, along with increasing temperature, reduced the pH and DIC but increased the TA and pCO 2 . This large-scale bloom also turned the coastal waters from being an atmospheric CO 2 sink to a strong source, with the estimation of air-sea CO 2 fluxes about 1.69 ± 1.70, 2.28 ± 1.16, and 7.44 ± 5.84 mmol m -2 d -1 during the early-, late-, and after-bloom periods, respectively. This bloom event also promoted the formation of CaCO 3 and was an important source of low molecular weight organic acids. These new findings provide nuances for the current conversations on the role of biological processes in modulating marine carbonate system and the contribution of organic matter to alkalinity., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Marginal seas are highly productive and disproportionately large contributors to global air-sea CO 2 fluxes. Due to complex physical and biogeochemical conditions, the southern Yellow-East China Sea is an ideal site for studying carbonate chemistry variability. The carbonate system was investigated in the area in spring of 2017 and summer of 2018. Dissolved inorganic carbon (DIC) and total alkalinity (TA) concentrations were higher in the SYS than the ECS due to material from carbonate weathering and erosion carried by the Yellow River. High pH and low DIC and TA were observed in the Zhe-Min Coastal Current in spring due to high primary productivity caused by Changjiang River input and the Taiwan Warm Current. Temperature and biological activity were the primary drivers controlling the partial pressure of CO 2 (pCO 2 ) in the SYS, pCO 2 was controlled by primary productivity related to nutrients carried by the Changjiang River and physical mixing in the Changjiang River plume and inner/middle shelves of the ECS, whereas temperature was the dominant factor determining pCO 2 distributions in the ECS outer shelf waters influenced by the Kuroshio Current. Overall, the entire study area shifted from a CO 2 sink (-4.18 ± 5.60 mmol m -2 d -1 ) to a weak source (1.02 ± 4.87 mmol m -2 d -1 ) from spring to summer. Specifically, the SYS and ECS offshore waters changed from CO 2 sinks in spring to sources in summer, while the Changjiang River plume was always a CO 2 sink., Competing Interests: Declaration of competing interest The authors declare that they have no conflict of interest., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Three cruises were conducted during an Ulva prolifera bloom in 2018 off the Qingdao coast to observe early-, late-, and after-bloom characteristics. Spatio-temporal changes in dimethylsulfide (DMS), dimethylsulphoniopropionate (DMSP), and acrylic acid (AA) and their relationships with environmental parameters were examined. Mesocosm experiments tested the effect of nutrient on the release of biogenic sulfur compounds during the decline period. Biogenic sulfur concentrations contrasted with those in non-bloom regions and reached their highest values during the late-bloom period. The average sea-to-air DMS flux was about 5 times higher than those of non-bloom regions. The mean concentrations of DMS and DMSP in the enclosures were 3-5 times those of in-situ seawater. Biogenic sulfur release was promoted by the addition of high concentrations of nutrients as U. prolifera was declining. The contribution of the U. prolifera bloom to atmospheric DMS was estimated to be 125 kg S d -1 ., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Nitric oxide (NO) has been identified as a key physiological modulator and signaling molecule in animals and plants. However, due to its high reactivity, our knowledge of its production and consumption pathways in the ocean remain limited. Laboratory experiments showed that Ulva prolifera can produce NO, producing as much as 0.44 ± 0.04 nmol h -1 g -1 . During the growth period, U. prolifera released NO, but during the decay period NO was absorbed by U. prolifera and bacteria. Furthermore, field investigations examined NO concentrations in the coastal waters of the Yellow Sea off Qingdao, where the U. prolifera green tide occurred in summer 2018. The average concentrations of NO in the surface seawater were 70.2 ± 38.2 pmol L -1 and 18.9 ± 10.3 pmol L -1 in the late- and after-bloom periods, respectively. NO release by U. prolifera was the primary contributor to the high NO concentrations during the late-bloom period. The study area was a net source of NO to the atmosphere during the study period, with average NO sea-air fluxes from the Qingdao coastal waters being 1.5 × 10 -12  mol m -2 s -1 and 0.4 × 10 -12  mol m -2 s -1 in the late- and after-bloom periods, respectively. This study concluded that the coastal waters of the Yellow Sea off Qingdao contributed more NO to the atmosphere during the bloom of U. prolifera than afterward., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Distributions and variations of biogenic sulfur compounds including dimethylsulfide (DMS), dissolved and total dimethylsulfoniopropionate (DMSPd and DMSPt) and acrylic acid (AA) were investigated in coastal waters off Qingdao, China during the late-bloom and after-bloom periods of the Ulva prolifera bloom of 2015. DMSPd, DMS and AA concentrations after the bloom were significantly higher than during the late-bloom, but DMSPt concentrations in surface waters began to decrease. High concentrations of these compounds in the surface layer were associated with the bloom, with the exception of increased concentrations of DMSPt in the middle layer as decaying U. prolifera debris settled. The sea-to-air fluxes of DMS were estimated to be 18.08 and 24.24 μmol m - 2  d - 1 during the late-bloom and after-bloom, and about three times higher than the reported average fluxes of the Yellow Sea, which highlighted the impacts of U. prolifera blooms on DMS emissions., Competing Interests: Declaration of competing interest We declare that we have no financial and personal relationships with other people or organizations that can inappropriately influence our work, there is no professional or other personal interest of any nature or kind in any product that could be construed as influencing the position presented in the manuscript entitled., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Dimethylsulfoniopropionate (DMSP) and nitric oxide (NO) in marine microalgae are considered as two important compounds involved in a variety of physiological functions. We examined the NO responses and the growth of Isochrysis galbana Parke and Gymnodinium sp. when supplemented with different concentrations of DMSP solutions in the cultures. Production of DMSP and dimethylsulfide (DMS) in Amphidinium carterae and Emiliania Huxleyi was investigated after the addition of NO donor sodium nitroprusside (SNP) and NO solution to algal media. The release peaks of NO were observed in cell suspensions of I. galbana Parke and Gymnodinium sp. immediately after the injection of DMSP solutions. The growth of these two microalgae was found to be significantly promoted or inhibited caused by exogenous DMSP. There was a decrease of DMSP concentrations in algal cultures within 24 h, accompanied with an increase in DMS, due to the effect of NO. The results provided direct evidence to confirm that there exist mutual effects of DMSP and NO during the growth of marine microalgae, which is speculated to be related to their roles as signaling molecules in planktonic communities., (Copyright © 2014 Elsevier Inc. All rights reserved.)

As an important signaling molecule, nitric oxide (NO) plays diverse physiological functions in plants, which has gained particular attention in recent years. We investigated the roles of NO in the growth of marine phytoplankton Platymonas subcordiforms and Skeletonema costatum under abiotic stresses. The growth of these two microalgae was obviously inhibited under non-metal stress (sodium selenium, Na2SeO3), heavy metal stress (lead nitrate, Pb(NO3)2), pesticide stress (methomyl) and UV radiation stress. After the addition of different low concentrations of exogenous NO (10(-10)-10(-8) mol L(-1)) twice each day during cultivation, the growth of these two microalgae was obviously promoted. Results showed that NO could relieve the oxidative stresses to protect the growth of the two microalgae. For different environmental stress, there is a different optimum NO concentration for marine phytoplankton. It is speculated that the protective effect of NO is related to its antioxidant ability., (Copyright © 2013 Elsevier Inc. All rights reserved.)