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Abstract: The Tl concentrations and chemical speciation were determined in the surface sediments of Bohai Bay to evaluate its biogeochemical characteristics. The total Tl concentrations were in the range of 0.506–0.770 μg/g and correlated significantly with clay and total organic carbon (TOC) contents, suggesting that the grain size and TOC were major factors controlling Tl distribution. The sequential extraction performed to indicate Tl speciation and availability in Bohai Bay sediments suggested that Tl occurred mainly in the residual fraction and Tl came mainly from natural input. In the non-residual fractions, Fe–Mn oxide and organic matter fractions accounted for the main portions, suggesting that the labile Tl adsorption was dominated by Fe–Mn oxides and organic matter. In addition, according to our estimate, about 2.7 t/yr and 0.16 t/yr of Tl reached Bohai Bay via rivers and atmosphere, respectively. [Copyright &y& Elsevier]

Comprehensive surveys were conducted in the Kocebu deep seamount and the M4 shallow seamount in the Western Pacific Ocean in March 2018 and May 2019, respectively. The distributions of nutrients in euphotic zone of the two seamount-areas were revealed, and the causative controlling factors were analyzed. Results show that the vertical distribution of nutrients in the two seamount-areas accorded with the general law of the oligotrophic ocean. The concentrations of NO3-N, PO4-P, and SiO3-Si generally increased gradually with the increase of water depth, and they were extremely low in water layers within 100 m. The area of high NO2-N concentration well agreed with the Deep Chlorophyll Maximum Layer. On the other hand, the distribution of water masses and phytoplankton and hydrological conditions in the two seamount-areas were different, resulting in lower concentrations of NO3-N, PO4-P, and SiO3-Si in the water layers below 100 m in the Kocebu seamount area than those in the M4 seamount area. In addition, NO2-N was affected by the distribution of phytoplankton, and distributed mainly in the water layers of 150 and 100 m. There was upwelling in the euphotic zone of M4 seamount area, causing accumulations of nutrients and phytoplankton around the seamount, forming a "seamount effect"; however, no such an effect was found in Kocebu seamount area. Affected by the composition of biological community and the "seamount effect", the nitrogen limitation in the M4 seamount area was not significant, and the dissolved inorganic nitrogen (DIN):PO4-P and SiO3-Si:DIN were closer to the Redfield ratios. [ABSTRACT FROM AUTHOR]

• Multiple indications of BHPs were evaluated in the East China Sea for the first time. • Two end-member model of R soil was applied to quantify OM source allocation. • BHT-isomer ratio of 0.20–0.45 is proposed as a threshold value to indicate hypoxia. • CH 4 oxidation markers have potential to reflect aerobic methane oxidation activity. The bacterial biomarker group of bacteriohopanepolyols (BHPs) has shown a significant potential to track terrestrial inputs and to respond to environmental changes. A total of 12 BHPs were detected in surface sediments of the East China Sea (ECS), with the contents of 3.79–361 μg/g TOC. The spatial distribution patterns and correlation analyses of bacteriohopanetetrol (BHT) and soil marker BHPs in sediments of the ECS indicate that they were mainly derived from marine autochthonous and terrestrial sources, respectively. The R soil index presented an "offshore decrease" trend, with the contribution of terrestrial organic matter (OM) decreasing from 63% in the coastal waters to 0.81% in the outer seas. This suggests that sedimentary OM in the coastal waters is mainly from terrestrial sources while that in the outer seas is dominantly from marine sources. The spatial distribution patterns and correlation analyses suggest mainly marine sources for the BHT-isomer in the ECS. Thus, although the co-eluted BHT-x and BHT-34R cannot be distinguished, the BHT-isomer in the ECS may be mainly BHT-x derived from marine bacteria rather than BHT-34R derived from terrestrial bacteria. Zones with high value of BHT-isomer ratios in sediments were consistent with the seasonal hypoxic zones in the ECS; furthermore, these ratios were negatively correlated with dissolved oxygen concentrations in the bottom waters. These results indicate that hypoxic environments are beneficial to BHT-isomer production, further confirming that the BHT-isomer can be a biomarker for marine hypoxia. Aminotetrol and aminopentol were closely related to the aerobic methane-oxidation gene pmoA and dissolved CH 4 , suggesting their potential as markers for aerobic methane oxidation. [ABSTRACT FROM AUTHOR]

To identify the sedimentary organic matter (OM) sources and reconstruct primary productivity evolution process in the coastal areas of the East China Sea (ECS), carbon, nitrogen and carbon stable isotope (δ13C) combined with sterols were studied in the surface and core sediments. The quantitative calculations of δ13C model and characteristic sterols suggested that the OM is derived from mixed marine and terrestrial inputs. Sinking marine phytoplankton was the dominant marine OM (MOM) source, with the average MOM proportion calculated by two end-member model of δ13C and characteristic sterol analysis of 73% and 62%, respectively. Terrestrial organic matter (TOM) displayed a decreasing trend seaward, attributed to the Changjiang River input as the dominant terrestrial source pathway. The decreased proportion of TOM with age in the core sediment was mainly controlled by the fluctuating changes of freshwater and sediment influxes of the Changjiang River. The sum content of epi-brassicasterol and dinosterol increased with age in recent 30 years, suggesting the increasing phytoplankton productivity. Enhanced anthropogenic nutrient inputs from the Changjiang River as well as the incremental nutrient supplement from the deep waters of the coastal upwelling area aggravated the phytoplankton blooms. Besides, the increasing ratio of epi-brassicasterol to dinosterol contents (B/D ratio) with age revealed the increasing diatom productivity relative to dinoflagellate productivity. This variation was mostly attributed to the natural forcing of the increased nutrient supplement from intensified coastal upwelling in the Zhejiang coastal mud area. • Marine organic matter input was the dominant source in the sediments. • Terrestrial organic matter was mainly controlled by the Changjiang River input. • The phytoplankton productivity increased during the past 30 years. • Increased diatoms compared with dinoflagellates was controlled by natural forcing. [ABSTRACT FROM AUTHOR]

Nutrients directly control the level of primary productivity and are crucial for the stability of marine ecosystems. Focusing on the survey results in August 2020 of the Yangtze River Estuary, this study elucidated the distribution characteristics and controlling factors of three nutrients: NO 3 -N, PO 4 -P, SiO 3 -Si. The results showed that the concentrations of NO 3 -N, PO 4 -P, SiO 3 -Si in the study area were generally higher near the shore than far shore, with average concentrations of 11.40, 0.70, and 23.73 μmol/L, respectively. The ocean currents drove the distribution of nutrients, and the transport of CDW and YSCC increased the nutrient levels. The resuspension of sediment caused by factors such as terrain and weather may lead to an abnormal increase in nutrients in the bottom waters. The main controlling factors of the three nutrients were different. NO 3 -N was significantly affected by human activities, PO 4 -P and SiO 3 -Si were mainly affected by natural factors., 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 process of atmospheric organic carbon (OC) entering the ocean through wet deposition plays a crucial role in the global carbon cycle. To gain insights into the biogeochemical dynamics of OC at the land-sea margin, we conducted an extensive four-year investigation on precipitation OC in Jiaozhou Bay (JZB). The results showed that the volume-weighted mean concentration of particulate OC (POC) and dissolved OC (DOC) in precipitation were 0.38 and 2.06 mg C L -1 with an average wet deposition flux of OC for 2666.5 mg C m -2  yr -1 . The source of POC in precipitation is predominantly by the C3 plant emission and burning and fossil fuel combustion. Wet deposition contributed 986.6 t yr -1 of OC of which 506.3 t yr -1 of bioavailable DOC, which could have significant implications for carbon cycle in the JZB. This study could enhance the understanding of the marine atmospheric OC in coastal areas., 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 behavior of heavy metals in contaminated sediment is of ecological significance considering the change of pH caused by ocean acidification. This study investigated the mobility of Cd, Cu, Ni, Pb, Fe, and Mn under experimental conditions for seawater acidification via enrichment of CO 2 gas at different reaction set-ups. The results indicated that the concerned metals behaved differently in the water compared to the sediment. The heavy metals were considerably transferred from sediment to seawater, and the resultant intensity was controlled by the degree of acidification and the chemical state of specific metals. Moreover, labile fractions of heavy metals in sediments were more susceptible to acidification than other fractions. These findings were observed and confirmed using real-time monitoring conducted via the diffusion gradient technique (DGT). Overall, the results of this study provided new insights into exploring the coupling risk of heavy metals with ocean acidification., 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.)

The development of marine carbon sequestration project has an important potential for carbon neutralization in the short-term (several decades). Marine carbon sequestration technology is based on biological and carbonate pumps to increase particulate organic carbon and authigenic insoluble carbonates to the deep sea or seafloor, aiming to achieve permanent carbon sequestration. Particularly, chemical carbon sequestration technology based on carbonate pump is proposed and considered to achieve short-term marine carbon sequestration in recent years. This technology mainly includes alkaline mineral addition and combining CO 3 2- to insoluble carbonates to improve marine carbon fixation capacity. Potential marine ecosystem risks of chemical CO 2 removal method should be considered before being a feasible technology. We reviewed the potential effects of marine chemical carbon sequestration project on marine organisms. Marine chemical carbon sequestration had two main effects on marine organisms: released chemicals effect, and particle effect. Released chemicals in mineral weathering directly affected phytoplankton and bacteria community. Particles formed during carbon sequestration process mainly affected filter feeding organisms. The toxic effects of particles on aquatic organisms increased with decreasing sizes and increasing concentrations of particle. Algae and crustaceans were the most sensitive groups exposed to metal nanoparticles (nm-μm) in seawaters, thus could be used as target species to evaluate ecological risk of small particles generated in chemical carbon sequestration project. Embryos or larva of filter feeding organisms were more sensitive to large clay and metal microparticles (μm‑mm) than adults, thus could be used as sensitive groups to establish safety concentration of large particles. The relatively inert metal nanoparticles and microparticles had higher safety concentrations than active ones. These particle concentration thresholds could be as a reference to design concentrations and initial sizes of applied minerals in marine chemical carbon sequestration project. This will ensure that the ecological risk is minimized when carbon fixation efficiency is maximized., 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.)

Fuzzy comprehensive assessment was applied, for the first time, to investigate the sediment environmental quality and compare the historical variations of heavy metal pollution in Daya Bay and Jiaozhou Bay, which are representative for sub-tropical and temperate zone of China, respectively. Results shown the Daya Bay had undergone three contrasting stages in the past 100 years. Before 1980s, the sediment was not contaminated by metals and its quality generally conformed to class I of China National Standard for marine sediment quality. During from 1980s to 2000s, however, Daya Bay's environment had experienced significant deterioration. The metal concentrations were significantly higher than the background values, suggesting that there was a sharp increase of metal input. The category of sediment quality fell to class II and class III. Copper was the dominant pollutant during that time. The good thing is sediment quality of Daya Bay has improved to class I since 2000s, and chromium turned to be the major pollutant. As for the Jiaozhou Bay, enrichment of heavy metal was generally not detected and the sediment quality strictly conformed to class I during the recent 90 years. Chromium and zinc were the major pollutants in this bay.

Coastal wetlands are terrestrial-marine transition zones harboring diverse active microbial communities. The origins of diverse glycerol ether lipids preserved in coastal wetlands are rarely investigated. 16 surface sediments were collected from the coastal wetland at Guangrao (GR), Changyi (CY) and Xiamen (XM), where both climate and sedimentary environment show significant differences. Ten groups of glycerol ether lipids, including isoprenoidal and branched glycerol dialkyl glycerol tetraethers (iGDGTs and bGDGTs), isoprenoidal and branched glycerol dialkanol diethers (iGDDs and bGDDs), hydroxylated isoprenoidal GDGTs and GDDs (OH-GDGTs and OH-GDDs), overly branched GDGTs (OB-GDGTs), sparsely branched GDGTs (SB-GDGTs), hybrid isoprenoid/branched GDGTs (IB-GDGTs) and a tentatively assigned H-shaped branched GDGTs (H-B-GDGTs) were detected and quantified. Sediments collected in the north (Guangrao and Changyi) contain, in general, a lower abundance of GDGT (3.7-55.9 ng/g sed) than samples from south (Xiamen; 251-1020 ng/g sed). iGDGTs and bGDGTs are the predominant components at all sites and account for 17.2-74.3% and 16.1-75.1% of total ether lipids, respectively. The relative abundance of iGDGTs decreases but that of bGDGTs increases with the distance from sea, suggesting a marine vs. terrestrial origin of iGDGT and bGDGTs, respectively. In addition, the methylation index (MI OB/B/SB ) of branched GDGTs shows a significant inverse correlation with water content, suggesting that marine waters have a major influence on the microbial communities inhabiting wetland sediment. Such an assumption was confirmed by the distinct lipid pattern of three low water content (<5%) samples collected in an area isolated from tidal flushing. The other isoprenoidal ether lipids, such as iGDDs, OH-GDGTs and OH-GDGTs, have a similar distribution as iGDGTs, indicating a common biological source, so do the corresponding non-isoprenoidal ether lipid series with bGDGTs. The BIT value increases with increasing distance from the sea, which implies that the BIT index can be probably applied to trace past sea level change in costal wetland settings. The reconstructed temperature from TEX 86 shows significant offset from observed data, but only little deviation for the MBT/CBT calculated temperature. This suggests that the MBT/CBT has the potential to reconstruct past temperatures in coastal wetland settings.

Antioxidant activity of kappa-carrageenan oligosaccharides (OM) and their chemical modification derivatives was investigated employing various established in vitro systems, such as reducing power, iron ion chelation, and total antioxidant activity using beta-carotene-linoleic acid system. The oversulfated (SD), lowly (LAD), and highly acetylated derivatives (HAD) in reducing power assay, the phosphorylated derivative (PD) in metal chelating assay, and oversulfated and phosphorylated derivatives in total antioxidant activity assay exhibited antioxidant activity higher than that of carrageenan oligosaccharides. The results indicated that the chemical modification of carrageenan oligosaccharides can enhance their antioxidant activity in vitro. The protective effects of the carrageenan oligosaccharides and their chemically modified derivatives against H(2)O(2) and UVA (long-wave ultraviolet radiation) induced oxidative damage on rat thymic lymphocyte were investigated by measuring cell viability via 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT). Thymic lymphocyte exposure to H(2)O(2) and UVA, a marked reduction in cell survival was observed, which was significantly prevented by carrageenan oligosaccharides and their derivatives (preincubated for 2h) at 66.7-2000 microg/mL. But both the carrageenan oligosaccharides and their different derivatives showed the similar protective effects on intracellular level. Taken together, these results suggest that carrageenan oligosaccharides and their derivatives show relevant antioxidant activity both in vitro and in a cell system.