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Tunable‐lifetime room‐temperature phosphorescence (RTP) materials have been widely studied due to their broad applications. However, only few reports have achieved wide‐range lifetime modulation. In this work, ultra‐wide range tunable‐lifetime efficient dark blue RTP materials were realized by doping methyl benzoate derivatives into polyvinyl alcohol (PVA) matrix. The phosphorescence lifetimes of the doped films can be increased from 32.8 ms to 1925.8 ms. Such wide range of phosphorescence lifetime modulation is extremely rare in current reports. Moreover, the phosphorescence emission of the methyl 4‐hydroxybenzoate‐doped film is located in the dark blue region and the phosphorescence quantum yield reaches as high as 15.4 %, which broadens their applications in organic optoelectronic information. Further studies demonstrated that the reason for the tunable lifetime was that the magnitude of the electron‐donating ability of the substituent group modulates the HOMO–LUMO and singlet‐triplet energy gap of methyl benzoate derivatives, as well as the ability to non‐covalent interactions with PVA. Moreover, the potential applications of luminescent displays and optical anti‐counterfeiting of these high‐performance dark blue RTP materials have been conducted. [ABSTRACT FROM AUTHOR]

Tunable‐lifetime room‐temperature phosphorescence (RTP) materials have been widely studied due to their broad applications. However, only few reports have achieved wide‐range lifetime modulation. In this work, ultra‐wide range tunable‐lifetime efficient dark blue RTP materials were realized by doping methyl benzoate derivatives into polyvinyl alcohol (PVA) matrix. The phosphorescence lifetimes of the doped films can be increased from 32.8 ms to 1925.8 ms. Such wide range of phosphorescence lifetime modulation is extremely rare in current reports. Moreover, the phosphorescence emission of the methyl 4‐hydroxybenzoate‐doped film is located in the dark blue region and the phosphorescence quantum yield reaches as high as 15.4 %, which broadens their applications in organic optoelectronic information. Further studies demonstrated that the reason for the tunable lifetime was that the magnitude of the electron‐donating ability of the substituent group modulates the HOMO–LUMO and singlet‐triplet energy gap of methyl benzoate derivatives, as well as the ability to non‐covalent interactions with PVA. Moreover, the potential applications of luminescent displays and optical anti‐counterfeiting of these high‐performance dark blue RTP materials have been conducted. [ABSTRACT FROM AUTHOR]

Developing pure organic single-component stimuli-responsive room-temperature phosphorescence (RTP) is of great significance but challenging. Herein, multiple stimuli-responsive RTP emitters are explored from the single-component neat molecular crystals of the analogues of drug raloxifene. The important role of the antiparallel molecular packing in the stimuli-responsiveness and RTP properties is clearly expounded. Advanced optical information encryption is realized by virtue of the polymorph conversion. The present work would shed light on the rational design of multi-stimuli responsive RTP systems based on single-component organics, drugs, and so on. [Display omitted] Simultaneously achieving room-temperature phosphorescence (RTP) and multiple-stimuli responsiveness in a single-component system is of significance but remains challenging. Crystallization has been recognized to be a workable strategy to fulfill the above task. However, how the molecular packing mode affects the intersystem crossing and RTP lifetime concurrently remains unclear so far. Herein, four economic small-molecular compounds, analogues of the famous drug raloxifene (RALO), are facilely synthesized and further explored as neat single-component and stimuli-responsive RTP emitters via crystallization engineering. Thanks to their simple structures and high ease to crystallize, these raloxifene analogues function as models to clarify the important role of molecular packing in the RTP and stimuli-responsiveness properties. Thorough combination of the single-crystal structure analysis and theoretical calculations clearly manifests that the tight antiparallel molecular packing mode is the key point to their RTP behaviors. Interestingly, harnessing the controllable and reversible phase transitions of the two polymorphs of RALO-OAc driven by mechanical force, solvent vapor, and heat, a single-component multilevel stimuli-responsive platform with tunable emission color is established and further exploited for optical information encryption. This work would shed light on the rational design of multi-stimuli responsive RTP systems based on single-component organics. [ABSTRACT FROM AUTHOR]

There are limited reports about the transformation of pure organic room‐temperature phosphorescence (RTP) materials with multilevel stimuli‐responsiveness at different RTP emission wavelengths under external stimuli. It is difficult to ensure efficient intersystem crossing (ISC) in different states of a single‐component system. This research reports the conversion of the organic single‐component small molecule 1,2‐bis(4‐alkoxyphenyl)ethane‐1,2‐dione (N‐BOX) with multilevel stimuli‐responsiveness between high‐efficiency blue and yellow RTP by grinding or thermal annealing N‐BOX crystals. The RTP emission of N‐BOX in the crystalline state was easy to adjust by external stimuli (grinding or thermal annealing) due to its non‐compact packing, which led to a phase transition and generated unique multilevel stimuli‐responsiveness. In particular, the RTP quantum yield of 7‐BOX with multilevel stimuli‐responsiveness reached 68.4 %, which provides an opportunity for regulation of smart optical materials based on pure organic RTP. [ABSTRACT FROM AUTHOR]

There are limited reports about the transformation of pure organic room‐temperature phosphorescence (RTP) materials with multilevel stimuli‐responsiveness at different RTP emission wavelengths under external stimuli. It is difficult to ensure efficient intersystem crossing (ISC) in different states of a single‐component system. This research reports the conversion of the organic single‐component small molecule 1,2‐bis(4‐alkoxyphenyl)ethane‐1,2‐dione (N‐BOX) with multilevel stimuli‐responsiveness between high‐efficiency blue and yellow RTP by grinding or thermal annealing N‐BOX crystals. The RTP emission of N‐BOX in the crystalline state was easy to adjust by external stimuli (grinding or thermal annealing) due to its non‐compact packing, which led to a phase transition and generated unique multilevel stimuli‐responsiveness. In particular, the RTP quantum yield of 7‐BOX with multilevel stimuli‐responsiveness reached 68.4 %, which provides an opportunity for regulation of smart optical materials based on pure organic RTP. [ABSTRACT FROM AUTHOR]

The ocean could profoundly modulate the ever-increasing atmospheric CO2 by air-sea CO2 exchange process, which is also able to cause significant changes of physical and biogeochemical properties in return. In this study, we assessed the long-term average and spatial-temporal variability of global air-sea CO2 exchange flux (FCO2) since 1980s basing on the results of 18 Coupled Model Intercomparison Project Phase 6 (CMIP6) Earth System Models (ESMs). Our findings indicate that the CMIP6 ESMs simulated global CO2 sink in recent three decades ranges from 1.80 to 2.24 Pg C/a, which is coincidence with the results of cotemporaneous observations. What's more, the CMIP6 ESMs consistently show that the global oceanic CO2 sink has gradually intensified since 1980s as well as the observations. This study confirms the simulated FCO2 could reach agreements with the observations in the aspect of primary climatological characteristics, however, the simulation skills of CIMP6 ESMs in diverse open-sea biomes are unevenness. None of the 18 CMIP6 ESMs could reproduce the observed FCO2 increasement in the central-eastern tropical Pacific and the midlatitude Southern Ocean. Deficiencies of some CMIP6 ESMs in reproducing the atmospheric pressure systems of the Southern Hemisphere and the El Niño-Southern Oscillation (ENSO) mode of the tropical Pacific are probably the major causes. [ABSTRACT FROM AUTHOR]

As a serious consequence of ocean warming and increased stratification, a rapid decrease in dissolved oxygen (DO) content of the world's oceans has attracted more and more attention recently. In open oceans, the decline of DO is characterized by the expansion of oxygen minimum zones (OMZs) in the ocean interior. Vast OMZs exist within the mesopelagic zones of the Tropical Western Pacific (TWP), but have gained very little attention. In this study, we focus on characteristics of OMZs in three typical seamounts areas (named Y3, M2, and Kocebu, respectively) of the TWP. Based on distributions of DO, the OMZs of the three seamounts areas are very different in scope, thickness, and the minimum oxygen content. The significantly different characteristics of OMZs at the seamounts are mainly because they are located in regions affected by different ventilation and consumption characteristic. To quantitatively describe the intensity of OMZs, a parameter, IOMZ, is firstly proposed. According to this quantitative parameter, the intensity order of OMZs for the three seamounts areas is Kocebu>M2>Y3. Potential biogeochemical effects of OMZs in the three seamounts areas are discussed using IOMZ. With higher IOMZ, the degradation particulate organic carbon (POC) tends to be lower. Yet because of the limited data, their relationship still need more research to prove. However, if this relationship holds in global oceans, the presence of seamounts would—under climate warming with expanding OMZs—promote vertical transport of POC resulting in an enhanced biological pump. Our study provides a new way to quantitatively study the impact of OMZs on the efficiency of biological pump. [ABSTRACT FROM AUTHOR]

The oxygen minimum zones (OMZs) are globally expanding, yet the variation pattern of microbial communities related to dissolved oxygen levels remain unclear. Spatial variability of bacterial diversity and community composition (represented by 16S rRNA) of six stations was investigated within the water column in the seamount area of Tropical Western Pacific Ocean (TWPO) in May 2019. The seawater has dissolved oxygen (DO) concentration of 3.01–6.68 mg/L and the core of the oxygen minimum zones was located between the depths of 650 m and 1 750 m. The bacterial alpha-diversity showed unimodal pattern with the decreasing DO with depths and peaked in the upper oxycline (UO) of OMZs. The bacterial community structure of the mixed layer (ML) and the bottom layer clustered and separated from each other, while those of UO and the OMZ core (OM) clustered and overlapped. Overall, bacterial community composition transitioned from being Alphaproteobacteria and Gammaproteobacteria-dominant in ML to being Gammaproteobacteria and Nitrososphaeria/Deltaproteobacteria-dominant in UO and OM, and then changed to being Clostridia and unidentified_Actinobacteria-dominant in the bottom layer. Moreover, both bacterial alpha-diversity and the abundant classes fitted varying sectioned functions with DO. The DO solely explained 40.37% of the variation of bacterial community composition among layers (P<0.001). The predicted function profiling showed that the water column was predominant by chemoheterotrophy, cyanobacteria, and photoautotrophy in ML, by chemoheterotrophy and nitrate/sulfide cycling in UO and OM, and by chemoheterotrophy and fermentation in the bottom layer. Our findings revealed the DO-associated variation in bacterial diversity and community composition, and help to clarify the potential responses of microbes and their involved biogeochemical processes to the expansion and intensification of OMZs. [ABSTRACT FROM AUTHOR]

Comprehensive surveys were conducted in the Kocebu deep seamount and the M5 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 M5 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 M5 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 M5 seamount area was not significant, and the dissolved inorganic nitrogen (DLN):PO4-P and SiO3-Si:DIN were closer to the Redfield ratios. [ABSTRACT FROM AUTHOR]

Spatial variations of sediment microbes pose a great challenge for the estimation of anthropogenic influence on biogeochemical processes, yet remain very unclear in coastal ecosystems. Surface sediments in 9 stations from the eutrophic Jiaozhou Bay, China, were sampled, DNA was extracted within the sediments, and the 16S rDNA was sequenced with the Illumina Hiseq sequencing. Results reveal considerable heterogeneity of sediment bacteria in the Jiaozhou Bay, of which Proteobacteria and Bacteroidetes accounted for over 75%. Bacterial alpha-diversity indices decreased generally from the outside to the inner part of the bay and from the offshore to the nearshore area. Bacterial community structures of S3, S4, S7, and S8 clustered, those of S5, S13, and S14 grouped together, while those of S6 and S10 were distinct from each other and from those of the other stations. Major class Gammaproteobacteria were more abundant at the stations with mesoeutrophic to eutrophic levels (S4, S5, S8, and S10) and less abundant at oligotrophic stations (S6, S13, and S14), while Deltaproteobacteria had an opposite distribution pattern. Overall, bacterial community composition transitioned from being Xanthomonadales-dominant at S4 and S8 to being unidentifed_Gammaproteobacteria-dominant at S5, S6, S13, and S14, while in other stations there were comparable orders. The biogeochemical processes correspondingly changed from being nitrogen cycling-dominant at S4 and S8 to being sulfur cycling-dominant at S5, S6, S13, and S14. The bacterial distribution patterns were especially affected by the factors (dissolved organic phosphorus, DOP) in the overlying seawater due to the habitat status of P-insufficiency in the bay. Both orders Xanthomonadales and Alteromonadales could serve as bioindicators of anthropogenic pollution to different pollution types. At last, divergent distribution patterns of individual bacterial populations in the bay were revealed, the influential environmental gradients were clarified, and the uncertainty of microbes was reduced, helping to predict environmental functions in coastal areas. [ABSTRACT FROM AUTHOR]

The continuous uptake of anthropogenic CO2 by the ocean leads to ocean acidification, which is an ongoing threat to the marine ecosystem. The ocean acidification rate was globally documented in the surface ocean but limited below the surface. Here, we present a monthly four-dimensional 1°×1° gridded product of global seawater pH, derived from a machine learning algorithm trained on pH observations at total scale and in-situ temperature from the Global Ocean Data Analysis Project (GLODAP). The constructed pH product covers the years 1992–2020 and depths from the surface to 2 km on 41 levels. Three types of machine learning algorithms were used in the pH product construction, including self-organizing map neural networks for region dividing, a stepwise algorithm for predictor selection, and feed-forward neural networks (FFNN) for non-linear relationship regression. The performance of the machine learning algorithm was validated using real observations by a cross validation method, where four repeating iterations were carried out with 25 % varied observations for each evaluation and 75 % for training. The constructed pH product is evaluated through comparisons to time series observations and the GLODAP pH climatology. The overall root mean square error between the FFNN constructed pH and the GLODAP measurements is 0.028, ranging from 0.044 in the surface to 0.013 at 2000 m. The pH product is distributed through the data repository of the Marine Science Data Center of the Chinese Academy of Sciences at http://dx.doi.org/10.12157/IOCAS.20230720.001 (Zhong et al., 2023). [ABSTRACT FROM AUTHOR]

Objectives: To compare the clinical significance of SF3B1/DNMT3A Comutations with SF3B1 or DNMT3A mutation alone in myelodysplastic syndrome (MDS) and clonal cytopenia of undetermined significance (CCUS).Methods: We identified and compared 31 patients with only DNMT3A mutation, 48 patients with only SF3B1 mutation, and 16 patients with only SF3B1/DNMT3A comutations.Results: SF3B1/DNMT3A comutations were found to be more common in MDS, whereas DNMT3A mutation alone was more common in CCUS. The patients with SF3B1/DNMT3A comutations were less likely to have poor cytogenetics than patients with DNMT3A mutation alone. Patients with SF3B1/DNMT3A comutations showed significantly longer median survival time and better overall survival than patients with DNMT3A mutation alone.Conclusions: Patients with SF3B1/DNMT3A comutations appear to have better clinical outcomes than patients with isolated DNMT3A mutation. These findings suggest that the favorable prognosis of SF3B1 mutation in is not abrogated by the concurrent presence of a DNMT3A mutation. [ABSTRACT FROM AUTHOR]

An investigation was carried out in the Y3 seamount area of the Western Pacific Ocean in December 2014, and the distribution of dissolved inorganic carbon (DIC) and its relationship with environmental factors in this area were explored. The results show that DIC concentration was higher in the adjacent waters of the Y3 seamount area, and the uplift of DIC isolines at the stations was close to the seamount. Meanwhile, interaction between the North Equatorial Current (NEC) and the Y3 seamount aff ected the DIC distribution, i.e., the upwelling in the same direction of the NEC was obvious, resulting in a decreasing trend of average concentration of DIC in the 200 m water column from the top to the two sides in this direction but in the cross direction. The DIC concentration increased with the water depth increase, and its distribution was aff ected by various environmental factors. In the surface water, high temperature was a decisive factor for the decrease of the DIC concentration, but the photosynthesis of phytoplankton showing only a weak influence. In the North Pacific Tropic Water (NPTW), DIC production rate from organic matter decomposition was higher than that of DIC consumption by phytoplankton photosynthesis, leading to a continual increase of DIC. In the North Pacific Intermediate Water (NPIW), organic matter decomposition played a leading role in the increase of DIC. In the deep water, decomposition of organic matter weakened, and the dissolution of CaCO3 controlled the carbonate system, and DIC had the smallest variation range. [ABSTRACT FROM AUTHOR]

To constrain the resuspension influence to the biogeochemical behavior of trace metals (TMs) in settling materials, the concentrations and chemical speciations of macro-elements (Al, Fe, Mn) and selected particulate TMs (V, Cr, Co, Cu, Zn, Ga, Sr, Cd, Ba, Tl, Pb, U) in trap-collected particles (TCPs), surface sediments (SS) and core sediment samples (CS5) of the Jiaozhou Bay were compared. Two approaches, mass conservation method and vertical two end-members mixing model, both calculated a resuspension ratio of more than 90%. Greater TM concentrations and Al-normalization levels than SS/CS5 determined the TCPs an important TM-sink, predominantly owing to grain-size effects and TCP-specific characteristics, i.e., structural capacity of organic-Fe associations for TMs' scavenging, preferential remineralization of TM than biogenic elements in autochthonous microorganisms. Comparison revealed distinct, Fe mineral controls on TM sequestration patterns: higher metal sequestration associated with amorphous Fe oxyhydroxides, while less reactive crystalline Fe oxides hold less metal. Nevertheless, turbulent hydrodynamics muted the wide TM retention divergences between TCP and SS, which should have happened based on different Fe minerals distribution for TCP/SS. The net effect of TM release by the organic carrier phase and then adsorption principally onto Mn/Fe oxyhydroxide phase for raised overall TCP-TM concentrations was also identified. • The resuspended ratios from sediments were estimated over 90% for Jiaozhou Bay. • Resuspended particles were important trace metal sinks for higher concentrations. • Effects of iron cycling and organic remineralization were evaluated. [ABSTRACT FROM AUTHOR]

Atmospheric aerosol samples over the western boundary regions of Pacific Ocean were collected during August 2014–October 2014 and November 2015–February 2016 on R/V Ke Xue , and concentrations of major water-soluble ions, NO 3 −, NO 2 −, NH4+, PO 4 3−, SO 4 2−, MSA−, Cl−, and Na+, were determined to study their seasonal distributions, sources and biogeochemical effect. The results showed that the average concentrations of NO 3 −, Cl− and Na+ were higher in winter, while the other ions had higher concentrations in summer. Most water-soluble ions presented obvious high-value centers in nearshore, indicating the significant influence of terrestrial input. Terrestrial input and marine emission were two major factors causing variation in concentrations of water-soluble ions, although their relative contributions were different in summer and winter. The average MSA/nss-SO 4 2− ratios in summer and in winter were 1.60% and 2.10%, respectively, based on which the contributions of anthropogenic sources to the total SO 4 2− were calculated to be 45.7% and 30.1% in summer and winter, respectively. Yet the contribution of biogenic sources to the total SO 4 2−, which was 14.9% in summer and 14.4% in winter, showed no seasonal change. Apart from air masses from Asian continent, air masses from Japan as well as from Indonesia were also important terrestrial sources of aerosol ions according to air mass backward trajectories analysis. Based on the distribution patterns of aerosol ions, the studied area was divided into Southeast China coastal sea area and Western Pacific open sea area, and the dry deposition fluxes of DIN for these two areas were 6166 μg m−2 day−1 and 574 μg m−2 day−1, which could support 5.6–19.4% and ~13.8% of the new production in the East China Sea and the Western Pacific, respectively. Therefore, atmospheric aerosols as an important medium for transporting nutrients to the study area should attract much attention. • Major water-soluble ions in aerosols over the western Pacific Ocean were examined. • Human sources contributed 45.7% and 30.1% of the total SO 4 2− in summer and winter, respectively. • The dry deposition of DIN could support ~13.8% of the new production in the Western Pacific. [ABSTRACT FROM AUTHOR]

Sediment resuspension in coastal environments is associated with both nutrient repartitioning and with the biological carbon pump, which are further linked to climate change, eutrophication, and marine pollution. To explore these relationships, a resuspension framework, including surficial/core sediments and settling trap-collected particles (TCPs), was assessed in the Jiaozhou Bay (JZB) to examine the behavior and fate of particulate biogenic elements (C, N, P and Si). Resuspension-mediated differences in the concentrations of numerous biogenic proxies were significant and mainly corresponded to selective upwelling of fine-sized, nutrient-enriched particles, to autochthonous organic matter degradation below the trap-deployed level comprising water column transportation and long-term retention at the sediment-water interface. This is further reinforced by smaller inorganic carbon concentrations in sediments and origin-indicating stoichiometric ratio records (OC:ON, OC:OP). Nevertheless, biogenic silica (BSi) exhibited a near homologous concentration and had the largest preservation efficiency. Three principal components, representing production and preservation, remineralisation, and a particle-size effect, accounted for 55.5%, 14.0%, and 9.1% of the total variance, respectively. After calibration, the primary sinking flux was two orders of magnitude smaller than the measured absolute sedimenting flux. Also, the limited bottom achieving contribution with a maximum of 28.3% for freshly biogenic particles produced in autumn/winter circumstances with low primary productivity was inferred. The recurrent resuspension processes in JZB demonstrated that 5–12 cycles of similar or higher intensity resuspension was required before freshly-formed biogenic particles could ultimately be integrated into the sediments. Regarding the internal P sink-switching mechanism, the previously transformed Fe-bound fraction across the estuarine salinity gradient has limited application under offshore redox oscillations, whereas near-quantitative transfer of dissolved P from remineralized organic matter to authigenic carbonate fluorapatite could substantially reduce its bio-availability in resuspended particulate P. • Biogenic element concentration in sinking particles is greater than sediments. • Resuspension correction downgraded sinking flux by two orders of magnitude. • Interior P sink-switching can reduce bio-availability of resuspended particles. [ABSTRACT FROM AUTHOR]

• The preservation efficiency of GDGTs in sediment of the ECS was estimated. • TEX 86 -derived SST matched well with the satellite-derived mean SST in autumn. • BrGDGTs were from terrestrial soils and used to reconstruct MAAT and soil pH. • Crenarchaeol and methane index could be used as potential palaeo-redox proxy. Glycerol dialkyl glycerol tetraethers (GDGTs) were determined in surface sediments from the East China Sea (ECS) in order to evaluate their potential for palaeo-climate and environmental reconstructions. Isoprenoid GDGTs (isoGDGTs) ranged from 516.75 ng/g to 1365 ng/g and crenarchaeol (cren) and caldarchaeol (GDGT-0) were the main components. IsoGDGTs were mainly derived from marine planktonic Thaumarchaeota. Branched GDGTs (brGDGTs) ranged from 12.3 ng/g to 123.5 ng/g and were dominated by GDGT-I and GDGT-II. The fractions and distributions, combined with branched/isoprenoid tetraether index (BIT) and methylation and cyclization indexes of brGDGT (MBT-CBT) suggested that brGDGTs in the ECS were mainly derived from terrestrial soils and they could be used to reconstruct climates. The TEX 86 -derived sea surface temperatures (SST) were close to the satellite-derived SST in autumn. The MBT/CBT-derived mean annual air temperatures (MAATs) and CBT-derived pH values in inner shelf by local and global calibrations matched well with the measured MAATs and soil pH in the lower Changjiang River basin, which seem to be appropriate for palaeo-climate and environment reconstructions of the continent around the ECS. Besides, cren and methane index showed a sensitive response to dissolved oxygen variation, suggesting their potential as palaeo-redox proxy. [ABSTRACT FROM AUTHOR]

• We investigated algal bloom effects on sediment-water interface arsenic dynamics. • Algal blooms aggravated sedimentary arsenic release, posing a marine pollution risk. • The main arsenic release pathway was microbially rather than geochemically mediated. • Algal bloom input mainly promoted microbial As(V) vs. Fe(III) reduction. • Changjiang Estuary summer algal blooms can cause 1440 kg of sedimentary As release. Algal blooms can aggravate arsenic (As) release from sediments and thus pose a pollution risk in the marine environment. However, the driving mechanism of algal blooms on sedimentary As cycling remains unclear. This study undertakes the first comprehensive examination of As release mechanisms under algal bloom conditions based on the evidence provided by temporal and depth profile changes of As species in the overlying water column, porewater and sediment, as well as As-related functional genes over the course of a 30-day incubation experiment using algal addition. The higher rate of increase of dissolved total As (dTAs) concentrations in a high biomass algal group (HAG) than an experimental control group (CG) suggested that algal degradation promoted the release of sedimentary As. The solid phase in all experimental groups remained rich in As(V), while in porewater As(III) and As(V) were the dominant As species during the initial rapid and subsequent slow degradation phases of organic matter, respectively, indicating that microbial reduction of As(V) and Fe(III) controlled the release of As during these two periods. A pronounced increase in arrA gene copies, and not a corresponding increase in the Geobacter copies, in HAG relative to CG supported the notion that algal blooms promoted microbial As(V) reduction. Additionally, the lower concentration of dissolved As(III) and cumulative dTAs flux in the sterilized-HAG treatment than in the sterilized-CG one further suggested that geochemically-mediated processes were not the main pathways of As release. Finally, it is estimated that summer algal blooms in the Changjiang Estuary can cause the release of 1440 kg of sedimentary As into the overlying water. [Display omitted] [ABSTRACT FROM AUTHOR]

The seasonal dynamics and diagenesis of trace metals at two contrasting coastal sites were studied to determine the mechanism that drove the diffusive release of trace metals from sediments in the Changjiang Estuary. Porewater trace metal concentrations were 53.4–4829 nM for Zn, 11.0–344 nM for Cu, 7.75–221 nM for Cr, 2.71–61.1 nM for Co, 0.822–42.7 nM for Pb and 0.037–4.22 nM for Cd. The concentrations and profiles of trace metals in the porewater and solid phase displayed obvious regional and seasonal variations. This variation was mainly reflected in the surface layer and the depth of the suboxic and anoxic layers. Regionally, surface porewater trace metal concentrations in the seasonal hypoxic region were higher than those in the aerobic region due to changes in the redox conditions being beneficial to the release of trace metals. Seasonally, surface porewater trace metal concentrations decreased in summer compared to spring due to their removal by forming metal sulfides in summer. Solid profiles of the trace metals supported their dynamic variations in the porewater. The partition coefficient suggested that the formation of Fe/Mn (hydr)oxides was effective for the removal of trace metal in oxidizing condition, while the formation of sulfides was conducive to the removal of trace metals in reducing condition. The combination of porewater with solid phase data suggested that the dynamics of Cu, Zn, Cr and Co were mainly controlled by Fe and Mn diagenesis, the dynamics of Cd were affected by S cycling, and the dynamics of Pb were disturbed by anthropogenic inputs and benthic organism activities. Estimation of benthic fluxes indicated that sediments were an important source of trace metals in the water column. The contributions of trace metals by sediments to the water column of the Changjiang Estuary were only one order of magnitude lower than those by riverine fluxes. Unlabelled Image • Seasonal dynamics of trace metals at SWI of the Changjiang Estuary are absent. • Mechanism that drove the diffusive release of trace metals at SWI was studied. • Seasonal cycling of trace metals was more obvious in the seasonal hypoxic zone. • Solid profiles of trace metals supported their dynamic variations in porewater. • Benthic diffusion was an important contributor to trace metals in water column. [ABSTRACT FROM AUTHOR]

A marine survey was conducted from 18 May to 13 June 2014 in the East China Sea (ECS) and its adjacent Kuroshio Current to examine the spatial distribution and biogeochemical characteristics of dissolved oxygen (DO) in spring. Waters were sampled at 10‒25 m intervals within 100 m depth, and at 25‒500 m beyond 100 m. The depth, temperature, salinity, and density (sigma-t) were measured in situ with a conductivity-temperature-depth (CTD) sensor. DO concentrations were determined on board using traditional Winkler titration method. The results show that in the Kuroshio Current, DO content was the highest in the euphotic layer, then decreased sharply with depth to about 1 000 m, and increased with depth gradually thereafter. While in the ECS continental shelf area, DO content had high values in the coastal surface water and low values in the near-bottom water. In addition, a low-DO zone off the Changjiang (Yangtze) River estuary was found in spring 2014, and it was formed under the combined influence of many factors, including water stratification, high primary productivity in the euphotic layers, high accumulation/ sedimentation of organic matter below the euphotic layers, and mixing/transport of oceanic current waters on the shelf. Most notable among these is the Kuroshio intruded water, an oceanic current water which carried rich dissolved oxygen onto the continental shelf and alleviated the oxygen deficit phenomenon in the ECS, could impact the position, range, and intensity, thus the formation/destruction of the ECS Hypoxia Zone. [ABSTRACT FROM AUTHOR]

Sedimentation rate and biogenic elements of a sediment core KET-1 recovered from Kuroshio Mainstream, east of Taiwan, were determined to investigate variation of organic carbon burial and its response to climate fluctuations. The results showed that the organic carbon burial flux was mainly depended on the sedimentation rate and the input of river particles had a dilution effect on total organic carbon (TOC) content of the sediment. Based on the organic carbon burial flux, the entire depositional process could be divided into three stages, which exactly corresponded to three specific climate periods over the past millennium. During the Medieval Warm Period (MWP, AD 1150-1250), the strong East Asian summer monsoon (EASM) caused more river input to the sea, resulting in high sedimentation rate and high organic carbon burial flux, meanwhile the dilution effect of river particles as well as low marine primary productivity resulted in relatively low proportion of marine organic matter (MOM) in the sediment, which was reflected by low TOC content. During the Little Ice Age (LIA, AD 1400-1835), lower organic burial flux and higher marine primary productivity as well as higher TOC content in the sediment were accompanied by weakened EASM. In the Modern Period (MP, AD 1835-present), however, the correlation between organic carbon burial and climate fluctuations that was found to be significant during the MWP and LIA had been greatly changed, and anthropogenic forcing was thought to be the primary driving factor. Overall, the climate variability and anthropogenic activities over the past millennium dominated the organic carbon burial in the sediment along the Kuroshio mainstream. [ABSTRACT FROM AUTHOR]

Abstract The spatial and temporal dynamics of both dissolved and particulate nutrients were studied during 2015–2016 in the Jiaozhou Bay (JZB), a deeply anthropogenic impact ecosystem in China. The dissolved inorganic nutrients was mainly from the wastewater and riverine inputs which is demonstrated from the negative correlation between nutrients with salinity and their higher levels distribution observed in the northeastern and/or northwestern JZB, where mainly received industrial and agricultural source run-off, respectively. The high levels of dissolved and particulate organic pools were also observed in the same area but have autochthonous sources besides terrestrial input, which lead to their higher concentrations in autumn during phytoplankton bloom. The composition of DIN has been changed with the major component from NH 4 + to NO 3 -, which probably due to the controlling load of NH 4 + but no limitation of NO 3 - by human intervention. The average annual DIN/DIP ratio increased by one time but SiO 3 2-/DIN ratio has no obvious variation over the past decade, which indicated that the potential limiting nutrient for phytoplankton growth has been converted from silicon to phosphorus in JZB. Additional, more prone to partition into POC but not DOC pools of organic carbon were found during the phytoplankton bloom in autumn due to the nutrient-rich, diatom dominated condition and both DOP and POP may be the potential P source and can relieve P limitation to some extent during the same time. Nutrient budgets calculation also demonstrated that riverine input and wastewater discharge are major sources of dissolved nitrogen and phosphorus, while silicate were mainly came from submarine fresh groundwater discharge. The mixing flow transported large amounts of nutrients from JZB to the Yellow Sea. Meanwhile, the net ecosystem metabolism and nitrogen metabolism calculation showed the whole ecosystem was heterotrophic and a net nitrogen fixation in JZB. Highlights • The composition of DIN in JZB has been changed with the major component from NH 4 + to NO 3 -. • The proportions of DON and DOP to TDN and TDP has increased obviously over the past decade. • The potential limiting nutrient for phytoplankton growth has been converted from silicon to phosphorus in JZB. • An annual nutrients budget including submarine fresh groundwater discharge is proposed. • JZB is net heterotrophic (57 ×107 mol C/yr) and net nitrogen fixation (74 ×106 mol/yr) on annual basis. [ABSTRACT FROM AUTHOR]

The sinks/sources of carbon in the Yellow Sea (YS) and East China Sea (ECS), which are important continental shelf seas in China, could exert a great influence on coastal ecosystem dynamics and the regional climate change process. The CO2 exchange process across the seawater-air interface, dissolved and particulate carbon in seawater, and carbon burial in sediments were studied to understand the sinks/sources of carbon in the continental shelf seas of China. The YS and the ECS generally have different patterns of seasonal air-sea CO2 exchange. In the YS, regions west of 124°E can absorb CO2 from the atmosphere during spring and winter, and release CO2 to the atmosphere during summer and autumn. The entire YS is considered as a CO2 source throughout the year with respect to the atmosphere, but there are still uncertainties regarding the exact air-sea CO2 exchange flux. Surface temperature and phytoplankton production were the key controlling factors of the air-sea CO2 exchange flux in the offshore region and nearshore region of the YS, respectively. The ECS can absorb CO2 during spring, summer, and winter and release CO2 to the atmosphere during autumn. The annual average exchange rate in the ECS was −4.2±3.2 mmol m−2 d−1 and it served as an obvious sink for atmospheric CO2 with an air-sea exchange flux of 13.7×106 t. The controlling factors of the air-sea CO2 exchange in the ECS varied significantly seasonally. Storage of dissolved inorganic carbon (DIC) and dissolved organic carbon (DOC) in the YS and the ECS were 425×106 t and 1364×106 t, and 28.2×106 t and 54.1×106 t, respectively. Long-term observation showed that the DOC content in the YS had a decreasing trend, indicating that the “practical carbon sink” in the YS was decreasing. The total amount of particulate organic carbon (POC) stored in the YS and ECS was 10.6×106 t, which was comparable to the air-sea CO2 flux in these two continental shelf seas. The amounts of carbon sequestered by phytoplankton in the YS and the ECS were 60.42×106 t and 153.41×106 t, respectively. Artificial breeding of macroalgae could effectively enhance blue carbon sequestration, which could fix 0.36×106-0.45×106 t of carbon annually. Organic carbon (OC) buried in the sediments of the YS was estimated to be 4.75×106 t, and OC of marine origin was 3.03×106 t, accounting for 5.0% of the TOC fixed by phytoplankton primary production. In the ECS, the corresponding depositional flux of OC in the sediment was estimated to be 7.4×106 t yr−1, and the marine-origin OC was 5.5×106 t, accounting for 5.4% of the phytoplankton primary production. Due to the relatively high average depositional flux of OC in the sediment, the YS and ECS have considerable potential to store a vast amount of “blue carbon.” [ABSTRACT FROM AUTHOR]

There are still limit reports to realize stimuli-responsive room-temperature phosphorescence (RTP) through molecular packing mode conversion of organic small compounds. Moreover, utilizing photoirradiation to regulate RTP emission behavior without chemical structure change, as a new kind strategy of functional optical material preparation, remains an interesting and challenging topic. Herein, we designed a new class of benzil derivatives: 1,2-bis (4-alkoxyphenyl) ethane-1,2-dione (BP-X). Among three molecules, 1,2-bis(4-(2-(2-(2-methoxyethoxy) ethoxy) ethoxy) phenyl) ethane-1,2-dione (BP-1) showed tangible and reversible phosphorescence conversion between cyan and green RTP under various external stimuli (mechanical force, thermal annealing and solvent fume). Besides, when irradiated with ultraviolet light, the molecular motion enhanced, leading to the packing mode of grinding state BP-1 reordering, which synchronously triggered its photo stimuli-responsiveness from green colour RTP emission back to cyan without destroying chemical structure. Both experimental and theoretical studies indicated that the multilevel stimuli-responsive phenomenon was attributed to molecular packing mode conversion and the alternation of molecular conformation of excited state. Such unique multilevel stimuli-responsive property supplies a facile strategy to enrich the advanced smart RTP materials. • The BP-1 displayed sensitive stimuli-responsive switching. Under various stimuli, due to the change of molecular packing mode, a new longer wavelength RTP emission would appear. • Photoirradation regulated luminescence, as a novel strategy in this work, was utilized to realize photo-responsive RTP conversion without molecular chemical structure change. • We achieved the reversible multicolour RTP conversion between green phosphorescence and cyan phosphorescence. [ABSTRACT FROM AUTHOR]

To probe the deposition velocities ( V d ), fluxes, origins and biogeochemical significance of atmospheric dry deposition (ADD) of nutrients in coastal waters, aerosol and dry deposition samples were collected in Jiaozhou Bay (JZB) from June 2015 to May 2016. We measured water-soluble inorganic nitrogen (WSIN; including ammonium (NH 4 N), nitrate (NO 3 N) and nitrite (NO 2 N)), organic nitrogen (WSON), inorganic phosphorus (WSIP; including reactive phosphate (PO 4 P)) and organic phosphorus (WSOP) for all samples. The concentrations of aerosol N species were comparatively higher than those in other aquatic ecosystems worldwide. Although WSIN and WSIP represented relatively large percentages of species, WSON (~16%) and WSOP (~35%) cannot be ignored in aerosols. The dry deposition fluxes for NH 4 N, NO 3 N, NO 2 N, WSON, PO 4 P and WSOP were 29.4, 29.9, 0.058, 15.4, 0.099 and 0.165 mmol m −2  yr −1 , respectively, with apparent seasonal variations. The average annual V d values of NH 4 N, NO 3 N, NO 2 N, WSON, PO 4 P and WSOP were indirectly calculated as 0.17 ± 0.11, 0.35 ± 0.20, 0.34 ± 0.25, 0.30 ± 0.22, 0.43 ± 0.28 and 0.91 ± 0.60 cm s −1 , respectively. The considerable differences between the percentages of corresponding nutrient concentrations and ADD fluxes were mainly attributed to V d variations. Anthropogenic emissions were the most common source of WSON and WSIN based on a correlation analysis. WSIP was highly correlated with WSOP, suggesting that they may share similar sources. Additionally, the long-range transport of natural and anthropogenic pollutants, especially the air-masses originating from the northwest direction, exerted greater effects than local emissions on aerosol N and P species in JZB based on an air mass backward trajectory analysis. The increasing ADD flux may have non-negligible biogeochemical effects on JZB by increasing primary productivity and altering the nutrient structure due to the high WSIN/WSIP ratio. [ABSTRACT FROM AUTHOR]

Protein rotation in viscous environments can be measured by fluorescence depletion anisotropy (FDA) which combines long lifetimes of chromophore triplet states with the sensitivity of fluorescence excitation and detection. FDA achieves sensitivity well beyond that attainable by the more common technique of time-resolved phosphorescence anisotropy (TPA). We have now combined benefits of both time-domain and frequency-domain FDA into a single continuous technique (CFDA). Intensity and polarization of a single laser beam are modulated continuously according to a complex, repeating waveform. Fluorescence signals excited from triplet-forming fluorescent probes are digitized over recurring waveform periods by a high-speed signal averager. CFDA experiments typically involve substantial ground state depletion. Thus signals, unlike those of TPA, are not linear in the exciting light intensity and simple data analysis based on such linearity is not appropriate. An exact solution of the coupled diffusion and triplet production/decay equation describing CFDA within individual data points has been combined with simulated annealing optimization to extract triplet and anisotropy decay kinetics from experimental data. Related calculations compare possible excitation waveforms with respect to rotational information provided per fluorescence photon. We present CFDA results for the model system of eosin conjugates of carbonic anhydrase, BSA and immunoglobulin G in 90% glycerol at various temperatures and initial cellular results on eosin-IgE bound to 2H3 cell Type I Fcε receptors. We explore how CFDA reflects rotational parameters of heterogeneous systems and discuss challenges of extending this method to single cell microscopic measurements. [ABSTRACT FROM AUTHOR]

Coastal hypoxic zones are expanding due to anthropogenic activities and climate changes. Increased hypoxia has greatly affected the marine nitrogen cycle. There are two typical seasonal hypoxic core areas in the north and south of the East China Sea (ECS). However, the interannual variations, north-south differences in hypoxia and their effects on the nitrogen cycle are still poorly understood. This study investigated bacteriohopanepolyols (BHPs), especially newly developed marine anammox bacteria and hypoxic biomarker bacteriohopanetetrol stereoisomer (BHT-x) and cyanobacterial nitrogen fixation biomarker 2-methyl BHT in two sediment cores, aiming to reconstruct hypoxia and nitrogen cycle records in the northern and southern hypoxic zones of the ECS over the last century. The results showed that BHT-x ratio in northern core 3100–2 presented higher values since 1960s (>0.2) and increased after 2000 (0.25–0.57), while it decreased in southern core DH6–1 after 2000 (0.03–0.11), indicating the continuously intensified hypoxia in the northern area and significantly weakened hypoxia in the southern area. Hypoxia is mainly associated with organic matter degradation and seawater stratification. The similar temporal increases of BHT-x ratios and marine-derived organic matter (MOM) contents in core 3100–2 suggest that eutrophication-driven MOM degradation is the main reason for hypoxia formation, which is exacerbated by strong water stratification there. Differently, although MOM contents still increased in core DH6–1 after 2000, the hypoxia weakened and even disappeared due to lessened stratification. In addition, the temporal variations of BHT-x and 2-methyl BHT in both cores indicated that anammox and nitrogen fixation simultaneously increased during periods of hypoxia. The co-variation suggests that hypoxia promotes anammox, and nitrogen loss may induce an increase in nitrogen fixation to compensate for nitrogen availability. • Regional differences of the ECS were evaluated by BHPs records for the first time. • Hypoxia and anammox prevailed since 1960s and intensified after 2000 in the north. • Hypoxia and anammox weakened after 2000 in the southern hypoxic zone. • Nitrogen fixation increased to compensate for nitrogen loss promoted by hypoxia. [ABSTRACT FROM AUTHOR]

From May to June 2014, the geochemical characteristics of dissolved barium (Ba) in sea water and its influx from the Kuroshio into the East China Sea (ECS) were studied by investigation of the Kuroshio mainstream east of Taiwan Island and the adjacent ECS. This allowed for the scope and extent of the Kuroshio incursion to be quantitatively described for the first time by using Ba as a tracer. The concentration of Ba in the Kuroshio mainstream increased gradually downward from the surface in the range 4.91-19.2 μg L. In the surface layer of the ECS, the Ba concentration was highest in coastal water and gradually decreased seaward, while it was higher in coastal and offshore water but lowest in middle shelf for bottom layer. The influx of Ba from Kuroshio into the ECS during May to October was calculated to be 2.19×10 kg by a water exchange model, in which the subsurface layer had the largest portion. The distribution of Ba indicated that Kuroshio upwelled in the sea area northeast of Taiwan Island. The north-flowing water in the Taiwan Strait restrained the incursion of Kuroshio surface water onto the ECS shelf, while Kuroshio subsurface water gradually affected the bottom of the ECS from outside. The results of end member calculation, using Ba as a parameter, showed that the Kuroshio surface water had little impact on the ECS, while the Kuroshio subsurface water formed an intrusion current by climbing northwest along the bottom of the middle shelf from the sea area northeast of Taiwan Island into the Qiantang Estuary, of which the volume of Kuroshio water was nearly 65%. Kuroshio water was the predominant part of the water on the outer shelf bottom and its proportion in areas deeper than the 100 m isobath could reach more than 95%. In the DH9 section (north of Taiwan Island), Kuroshio subsurface water intruded westward along the bottom from the shelf edge and then rose upward (in lower proportion). Kuroshio water accounted for 95% of the ocean volume could reach as far as 122°E. Ba was able to provide detailed tracing of the Kuroshio incursion into the ECS owing to its geochemical characteristics and became an effective tracer for revealing quantitative interactions between the Kuroshio and the ECS. [ABSTRACT FROM AUTHOR]

Objectives: To compare the mutational profiles of patients with primary myelofibrosis (PMF), polycythemia vera (PV), and essential thrombocytosis (ET).Methods: Next-generation sequencing results of 75 cases of PMF, 33 cases of PV, and 27 cases of ET were compared.Results: Mutation rates of ASXL1 and SRSF2 were significantly higher in PMF than in PV or ET. ASXL1 mutations appeared to be more frequently associated with risk of transformation to acute myeloid leukemia than JAK2 or TET2 mutations. The most common mutation-cytogenetic combinations in myeloproliferative neoplasm (MPN) were mutations of JAK2 or ASXL1 with del(20q) and were more common in patients with PMF and PV than in patients with ET. Differences were also found between patients with PMF and PV.Conclusions: PMF, PV, and ET show different mutational profiles, which may be helpful in resolving the differential diagnosis between MPNs. Due to the relatively small number of cases and variable testing over time, larger controlled studies are necessary to confirm the findings. [ABSTRACT FROM AUTHOR]

To analyze the fluxes, seasonal variations, sources and potential ecological effects of dissolved trace elements (TEs) in atmospheric wet deposition (AWD), one-year wet precipitation samples were collected and determined for nine TEs in Jiaozhou Bay (JZB) between June 2015 and May 2016. Both the volume-weighted mean (VWM) concentration and flux sequence for the measured TEs was Al > Mn > Zn > Fe > Pb > Se > Cr > Cd > Co. Al was the most abundant TE with a VWM concentration and wet flux of 33.8 μg L −1 and 29.2 mg m −2 yr −1 , which were 2 and 3 orders of magnitude higher than those of Co, respectively. The emission intensities of pollutants, rainfall amount and wind speed were the dominating factors influencing seasonal variations of TEs in AWD. Based on enrichment factors, correlation analysis and principal component analysis, most of the TEs in AWD were primarily originated from anthropogenic activities except for Al and Fe, which are typically derived from re-suspended soil dusts. Although the TE inputs by AWD were significantly lower than those by rivers, the TE inputs via short-term heavy rains would distinctly increase surface seawater TE concentrations and then pollute the marine environment of JZB. AWD would have both profound impacts on the biogeochemical cycles of TEs and dual ecological effects (nutrient and toxicity) on aquatic organisms. [ABSTRACT FROM AUTHOR]

Phosphorus (P) is an important macronutrient that can limit primary productivity in coastal marine ecosystems. In this study, four sediment cores were collected in the Jiaozhou Bay to study the phosphorus forms and their bioavailability, including exchangeable or loosely sorbed P (Ex-P), iron-bound P (Fe-P), authigenic P (Ca-P), detrital P (De-P) and organic P (OP), which were separated and quantified using a sequential extraction method (SEDEX). The results showed that the concentration of total P (TP) in core sediments ranged from 6.23 to 10.46 μmol/g, and inorganic P (IP) was the dominated P form. Fe-P and De-P were the main chemical forms of IP in core sediments. The profile variation of OP presented the most significant among the phosphorus forms. Whereas the concentrations of Ex-P, Fe-P, and Ca-P varied slightly with depth, indicating that the transformation of Ex-P, Fe-P, Ca-P, and OP could occur during sedimentary P burial. Moreover, the distribution of P species was influenced by many factors, including terrigenous input, biological processes, organic matter degradation and increasing human activities. High total organic carbon (TOC)/OP ratio occurred in the Jiaozhou Bay, ranging from 73 to 472 (average, 180 ± 81) in core sediments, which was caused by the increasing terrestrial organic matter. The ratio of TOC/P reactive ranged from 24 to 101 (average 46 ± 15) in core sediments (lower than the Redfield ratio), implying a surplus of sedimentary reactive P compared with TOC. Potential bioavailable P (BAP) accounted for about 28.2–60.8% (average, 47.1 ± 7.4%) of TP in core sediments, and presented an increasing trend since 1980s, which might be responsible for the shift of phytoplankton community composition during these decades. [ABSTRACT FROM AUTHOR]

Atmospheric wet deposition (AWD) is an important pathway for anthropogenic and natural pollutants entering aquatic ecosystems. However, the study on the magnitudes and ecological effects of AWD of various nutrient species (nitrogen, phosphorus and silicon) on Jiaozhou Bay is scarce. To address these issues, in this study, wet deposition samples were collected at a coastline site along Jiaozhou Bay from June 2015 to May 2016. Dissolved inorganic nitrogen (DIN, including NH 4 –N, NO 3 –N and NO 2 –N), dissolved organic nitrogen (DON), dissolved inorganic phosphorus (DIP, i.e. PO 4 –P), dissolved organic phosphorus (DOP) and reactive silicate (SiO 3 –Si) were analyzed. The volume-weighted mean (VWM) concentrations of NH 4 –N, NO 3 –N and DON in AWD were higher compared with those of NO 2 –N, PO 4 –P, DOP and SiO 3 –Si. The annual influxes of NH 4 –N, NO 3 –N, NO 2 –N, DON, DIP, DOP, and SiO 3 –Si via AWD were 92.8, 54.5, 0.427, 47.5, 0.274, 0.448 and 1.73 mmol·m − 2 ·yr − 1 respectively; NH 4 –N and DOP were the dominant species for N and P, and the roles of DON and DOP in AWD could not be neglected. Significant seasonal variations were observed in concentrations and fluxes of all nutrient species owing to the effects of rainfall, the intensities of local emission sources and the long-distance transports of natural and anthropogenic pollutants. The major sources of N, Si and P in AWD were agricultural activities, soil dust and a mixing one involving both anthropogenic and natural sources, respectively. Though AWD represents relatively low percentages of external inputs for nutrients and low contribution to primary productivity (PP) of Jiaozhou Bay, large amounts of nutrient inputs originating from sudden heavy rains may enhance PP prominently, as well as aggravate P-limitation and Si-limitation and further affect phytoplankton community structures and size-fractioned structures with the quite high DIN:DIP ratios and extremely low Si:DIN ratios in AWD. [ABSTRACT FROM AUTHOR]

The coastal waters off the Changjiang Estuary are a seasonal hypoxic region, offering an ideal system for studying the geochemical cycles of redox sensitive elements (RSEs) at the sediment-water interface (SWI) and their response potential to redox changes. The profiles of porewater and solid RSEs and their chemical speciation and diffusive fluxes at five sites in two seasons were studied to evaluate the migration and removal of RSEs at the SWI off the Changjiang Estuary. Results showed that porewater and solid RSEs displayed the corresponding profile variations. The porewater Mo and U concentrations generally decreased with depth, attributed to the reductive removal. Particularly, the removal of Mo may be mediated by the Fe–S phase, and the removal of U appears to be via the microbially-mediated reduction. Porewater V, U and Mo were removed successively with depth, corresponding to the peaks of dissolved nitrate, Fe2+ and acid volatile sulfur (AVS). However, porewater V increased again in the deep layers due to its complexation with dissolved organic matter. The upward shift of RSE peaks in porewater and transformation depths of their oxidation states based on the model from spring to summer reflected the occurrence of hypoxia in summer. The downward diffusive fluxes of RSEs at hypoxic site in summer indicated their hypoxia-induced enrichment. The Mo–U covariation suggested that the seasonal hypoxic sites off the Changjiang Estuary were more favorable for the accumulation of authigenic U. • The profile and seasonal variations of RSEs at the SWI off the Changjiang Estuary were studied. • The porewater profiles of V, U and Mo showed the successive removal with depth. • Chemical speciation obtained by model reflected the reductive removal of RSEs. • The Mo–U covariation and diffusive fluxes indicated the summer hypoxia. [ABSTRACT FROM AUTHOR]

Nitrogen (N) and phosphorus (P) in suspended particles are important to the cycles of N and P in marine ecosystem. Suspended particles were collected from the East China Sea (ECS) and its adjacent Kuroshio waters to investigate the composing and distribution characteristics of particulate inorganic and organic nitrogen and phosphorus (PIN, PIP, PON and POP, respectively). The particulate N and P concentrations were fairly low in the Kuroshio water but much higher in the ECS water, especially in nearshore waters. PON and PIP were the dominant forms of particulate N and P, with an exception that POP was the major form of particulate P in the Kuroshio upper water. The regime of particulate N and P in the ECS was strongly influenced by riverine input, oceanic input, ocean current and photosynthesis. Among them, PON and POP were mainly from biogenic source, while PIN and PIP were originated from biogenic and external sources. And sedimentation, remineralization and resuspension were important influencing factors for the vertical distributions of particulate N and P. The budgets of particulate N and P for the ECS Shelf during rainy season (May–October) were also evaluated. The total particulate N and P (TPN and TPP) fluxes from oceanic input are respectively 10.99 and 2.49 times of those from riverine input. And oceanic input contains more POP, which is liable to be decomposed into phosphate, than riverine input. Furthermore, particulate nutrients fluxes from photosynthesis are the overriding source of total influxes for the ECS Shelf, accounting for 90.93% of TPN and 89.37% of TPP influxes. As for the photosynthetic fixed N and P, only 6.17% and 7.60% of them can reach the seafloor, while up to 87.73% and 60.06% of them are likely to be remineralized. The POP-rich oceanic input and the intensive photosynthesis and remineralization processes play important roles in the biogeochemical cycles of N and P in the ECS. [ABSTRACT FROM AUTHOR]

Vertical profiles of environmental radionuclides ( 210 Pb, 137 Cs, 238 U, 232 Th, 226 Ra and 4 0 K) in a sediment core (Y1) of the Yellow River Estuary wetland were investigated to assess whether environmental evolutions in the coastal wetland could be recorded by the distributions of radionuclides. Based on 210 Pb and 137 Cs dating, the average sedimentation rate of core Y1 was estimated to be 1.0 cm y −1 . Vertical distributions of natural radionuclides ( 238 U, 232 Th, 226 Ra and 40 K) changed dramatically, reflecting great changes in sediment input. Concentrations of 238 U, 232 Th, 226 Ra and 40 K all had significant positive relationships with organic matter and clay content, but their distributions were determined by different factors. Factor analysis showed that 238 U was determined by the river sediment input while 226 Ra was mainly affected by the seawater erosion. Environmental changes such as river channel migrations and sediment discharge variations could always cause changes in the concentrations of radionuclides. High concentrations of 238 U and 226 Ra were consistent with high accretion rate. Frequent seawater intrusion decreased the concentration of 226 Ra significantly. The value of 238 U/ 226 Ra tended to be higher when the sedimentation rate was low and tide intrusion was frequent. In summary, environmental evolutions in the estuary coastal wetland could be recorded by the vertical profiles of natural radionuclides. [ABSTRACT FROM AUTHOR]

Surface partial pressure of CO 2 ( p CO 2 ) and pertinent parameters (i.e., pH, total alkalinity, dissolved oxygen, chlorophyll a) were investigated in the southern Yellow Sea (SYS) and the East China Sea (ECS) basing on two surveys conducted in June and August of 2013. The results suggested carbonate chemistry dynamics and related controlling factors were provided with significant temporal and spatial variations in different subregions of these two continental shelf seas. The western of SYS (SYSW) was CO 2 -undersaturated both in June and August, with the average F CO 2 −1.88 mmol m −2 d −1 and −3.72 mmol m −2 d −1 , respectively. The phytoplankton initiated CO 2 -absorption and the suspended sediment induced CO 2 -emission jointly controlled the air–sea CO 2 exchange there. The center of SYS (SYSC) also behaved as an obvious CO 2 sink (−1.57 mmol m −2 d −1 and −3.99 mmol m −2 d −1 in June and August, respectively), probably due to elevated TA/DIC ratio and the subsequent effects of spring bloom. As for the Yangtze River estuary (YRE), it changed from an obvious CO 2 sink (−1.28 mmol m −2 d −1 ) in June into a very weak CO 2 source (0.04 mmol m −2 d −1 ) in August. This change was probably associated with the rising of seawater temperature and monthly variation of Yangtze River discharge. The inner shelf of ECS (ECSS) experienced obvious air–sea CO 2 flux changes during from June (−8.88 mmol m −2 d −1 ) to August (−0.36 mmol m −2 d −1 ) as well. Biological DIC consumption in the upper layer and DIC regenerated from respiration in the subsurface jointly controlled this p CO 2 variation. As a whole, the SYS and ECS acted as an obvious CO 2 sink during summer and could absorb atmospheric CO 2 with the average air–sea flux ( F CO 2 ) −2.68 mmol m −2 d −1 . The summary of air–sea CO 2 flux in the ECS and SYS during recent two decades indicated the ECS served as quite a stable CO 2 sink, whereas the SYS experienced obvious change. Discharge of Yangtze River and anthropogenic nutrients loading could profoundly affect the variations of p CO 2 and F CO 2 in future. [ABSTRACT FROM AUTHOR]

The turbidity maximum zone (TMZ) is one of the most important regions in an estuary. However, the high concentration of suspended material makes it difficult to measure the partial pressure of CO ( pCO) in these regions. Therefore, very little data is available on the pCO levels in TMZs. To relatively accurately evaluate the CO flux in an example estuary, we studied the TMZ and surrounding area in the Changjiang (Yangtze) River estuary. From seasonal cruises during February, August, November 2010, and May 2012, the pCO in the TMZ and surrounding area was calculated from pH and total alkalinity (TA) measured in situ, from which the CO flux was calculated. Overall, the TMZ and surrounding area acted as a source of atmosphere CO in February and November, and as a sink in May and August. The average FCO was −9, −16, 5, and 5 mmol/(m·d) in May, August, November, and February, respectively. The TMZ's role as a source or sink of atmosphere CO was quite different to the outer estuary. In the TMZ and surrounding area, suspended matter, phytoplankton, and pH were the main factors controlling the FCO, but here the influence of temperature, salinity, and total alkalinity on the FCO was weak. Organic carbon decomposition in suspended matter was the main reason for the region acting as a CO source in winter, and phytoplankton production was the main reason the region was a CO sink in summer. [ABSTRACT FROM AUTHOR]

The partial pressure of CO2 (pCO2) and air-sea CO2 exchange flux (FCO2) in the southern Yellow Sea (SYS, 120–125°E, 31.5–37°N) were investigated basing on the field surveys conducted in April of 2011, and June, July, October of 2012. With significant spatial variations, surface pCO2 ranged from 243 to 574μatm, 206 to 620μatm, 102 to 655μatm and 328 to 557μatm in April, June, July and October, respectively. Nearshore area of Shandong Peninsula and Jiangsu Shallow (depth<50m) were pCO2-supersaturated (pCO2=400–600μatm), as the result of intensive water mixing which brought the bottom CO2-rich water to the surface layer. Conversely, offshore area of SYS center (depth>50m) was pCO2-undersaturated (pCO2<390μatm) in April, June and October, but supersaturated in July. Phytoplankton production sustained by abundant nutrient and suitable hydrodynamic conditions was of great importance for this undersaturated pCO2. Moreover, extreme low pCO2 (pCO2<300μatm) was observed in the Changjiang plume (32.5–33.5°N, 123–125°E) in July, which was also related with the biological uptake of CO2. Average air-sea CO2 exchange flux of the SYS in April, June, July and October was −3.16±0.40mmolm−2 d−1,−4.56±0.34mmolm−2 d−1, −0.36±0.51mmolm−2 d−1, and 6.67±0.57mmolm−2 d−1, respectively. As a whole, the SYS behaved as a weak CO2 sink during April to October, with an average flux for about −0.35mmolm−2 d−1. As for the controlling factors for pCO2 variation, temperature played the dominant role in October, whereas the non-temperature factors, such as vertical mixing, Changjiang plume and biological activity, were considered as the primary controlling factors in June and July. Spatially, the control of temperature on pCO2 was predominant in the offshore SYS; the non-temperature factors were predominant in the shallow nearshore area, especially in coast of Shandong Peninsula and the Jiangsu Shallow. [ABSTRACT FROM AUTHOR]

With the implementation of the GEOTRACES program, the biogeochemical cycle and distribution of tellurium (Te) in marine environments are becoming increasing environmental concerns. In this study, the concentration of dissolved Te in the Changjiang (Yangtze) River estuary and nearby waters was determined in May 2009 by hydride-generation atomic fluorescence spectrometry to elucidate the abundance, dominant species, distribution, and relationship with environmental factors. Results show that: (1) dissolved Te was low owing to its low abundance in the Earth's crust, high insolubility in water, and strong affinity to particulate matter; (2) Te(IV) and Te(VI) predominated in surface water. Te(VI) was the dominant species in bottom water, and Te(IV) was the minor species; (3) Horizontally, resulting from low phytoplankton metabolism and the weak reduction from Te(VI) to Te(IV) in the shore, Te(IV) was concentrated in the central zone instead of the coastal region. However, Te(VI) was abundant near the mouth of the Changjiang River where the Changjiang water is diluted and in the area to the south where the Taiwan Warm Current invaded. In the adsorption-desorption process, Te(IV) was negatively related to suspended particulate matter (SPM), indicating that it was adsorbed by particulate matter. While for Te(VI), the positive correlation with SPM suggested that it was desorbed from the solid phase. In the estuary, dissolved Te had a negative correlation to salinity. However, it deviated from the dilution line in high-salinity regions due to the invasion of the Taiwan Warm Current and the mineralization of organic matter. The relationship between Te(IV) and SPM nutrients indicated that it was more bioavailable and more related to phosphorus than to nitrogen. Progress in the field is slow and more research is needed to quantify the input of Te to the estuary and evaluate the biochemical role of organisms. [ABSTRACT FROM AUTHOR]

Biogenic elements and six phosphorus (P) fractions in surface sediments from the Changjiang Estuary and adjacent waters were determined to investigate the governing factors of these elements, and further to discuss their potential uses as paleo-environment proxies and risks of P release from sediment. Total organic carbon (TOC) and leachable organic P (Lea-OP) showed high concentrations in the estuary, Zhejiang coast and offshore upwelling area. They came from both the Changjiang River and marine biological input. Biogenic silicon (BSi) exhibited a high concentration band between 123 and 124°E. BSi mainly came from diatom production and its concentration in the inshore area was diluted by river sediment. Total nitrogen (TN) was primarily of marine biogenic origin. Seaward decreasing trends of Fe-bound P and Al-bound P revealed their terrestrial origins. Influenced by old Huanghe sediment delivered by the Jiangsu coastal current, the maximum concentration of detrital P (Det-P) was observed in the area north of the estuary. Similar high concentrations of carbonate fluorapatite (CFA-P) and CaCO 3 in the southern study area suggested marine calcium-organism sources of CFA-P. TOC, TN and non-apatite P were enriched in fine sediment, and Det-P partially exhibited coarse-grain enrichment, but BSi had no correlation with sediment grain size. Different sources and governing factors made biogenic elements and P species have distinct potential uses in indicating environmental conditions. Transferable P accounted for 14%–46% of total P. In an aerobic environment, there was low risk of P release from sediment, attributed to excess Fe oxides in sediments. [ABSTRACT FROM AUTHOR]

Measurements of pH, total alkalinity (TA), partial pressure of CO ( pCO) and air-sea CO flux ( FCO) were conducted for the inner continental shelf of the East China Sea (ECS) during August 2011. Variations in pCO distribution and FCO magnitude during the construction of the Three Gorges Dam (TGD) (2003-2009), and the potential effects of the TGD on the air-sea CO exchange were examined. Results showed that the ECS acts as an overall CO sink during summer, with pCO ranging from 107 to 585 μatm and an average FCO of −6.39 mmol/(m ·d). Low pCO (<350 μatm) levels were observed at the central shelf (28°-32°N, 123°-125.5°E) where most CO-absorption occurred. High pCO (>420 μatm) levels were found in the Changjiang estuary and Hangzhou Bay which acted as the main CO source. A negative relationship between pCO and salinity ( R=0.722 0) in the estuary zone indicated the predominant effect of the Changjiang Diluted Water (CDW) on the seawater CO system, whereas a positive relationship ( R=0.744 8) in the offshore zone revealed the influence of the Taiwan Current Warm Water (TCWW). Together with the historical data, our results indicated that the CO sink has shown a shift southwest while FCO exhibited dramatic fluctuation during the construction of the TGD, which is located in the middle reaches of the Changjiang. These variations probably reflect fluctuation in the Changjiang runoff, nutrient import, phytoplankton productivity, and sediment input, which are likely to have been caused by the operations of the TGD. Nevertheless, the potential influence of the TGD on the CO flux in the ECS is worthy of further study. [ABSTRACT FROM AUTHOR]

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]

Abstract: To understand the spatial and temporal distributions, environmental risks and sources of As, 38 surface sediments and three sediment cores were collected in the East China Sea (ECS). As concentrations in sediments ranged from 1.70 to 22.1μg/g with an average of 11.5μg/g. As concentration had positive correlations with clay+silt and total organic carbon (TOC) content with higher As values near the Changjiang Estuary and Hangzhou Bay mouth, indicating fine-grained sediments and riverine inputs as the main factors controlling As distribution. Chemical fraction analysis, sediment quality guidelines, together with geoaccumulation index, suggested that As in sediments of the ECS was at low risk, low adverse effect and moderately polluted level. Vertical profiles of As concentrations and burial fluxes, combined with 210Pb dating, reflected the As pollution history in the ECS within the last one hundred years. It showed a stable trend before one hundred years ago, a slight increase from the 1900s to 1990s, with peak values in the 1980s and 1990s, and a declining trend after the 1990s to 2009 with a relatively low value in 1998. These trends were closely associated with both natural and anthropogenic activities. [Copyright &y& Elsevier]

Abstract: Increasing eutrophication and seasonal anoxia in bottom water in the Changjiang Estuary and its adjacent waters has progressed in recent decades, caused by elevated anthropogenic N and P input. Sedimentary biogenic elements were investigated to determine whether the biogenic proxies could be used in paleoenvironmental studies in an energetic estuary, as well as to reconstruct the histories of environmental changes in the East China Sea (ECS). Two 210Pb-dated cores from the coastal and offshore waters were analyzed for organic C (TOC) and its stable isotope (δ13C), total N (TN), biogenic Si (BSi), total P (TP) and P species. In coastal sediment, the variations of P species, especially Fe-P, Al-P and detrital apatite P (Det-P), reflected the dry–wet oscillations in the Changjiang River for the past century, which has influenced the sediment grain size and terrestrial material input. Much lower BSi content (0.756%) at 16–22cm likely recorded the pronounced decrease in silicate flux in the Changjiang River and its lower flow in the late 1980s. In offshore sediment, higher concentrations of TOC, TN, BSi, Ex-P, Fe-P and Lea-OP indicated higher primary productivity in response to the strong winter monsoons during the 1960s–1980s, and their 20-a fluctuations were in agreement with the decadal variations of the winter monsoon. Low contents and little variations of Al-P and Det-P indicated the slight influence of the terrestrial sediment input in offshore waters. The influence of human activities on the environment in recent decades has also been recorded in coastal sediment. Grain-size normalized concentrations of TOC, TN, TP, Ex-P, Fe-P and Lea-OP increased by 24%, 23%, 15%, 13% and 51% in the upper 16cm of coastal sediment, indicating elevated P and N load and primary productivity since the 1990s. Elevated TN/TP ratios and decreased BSi/TOC recorded the changed nutrient structure and the decrease in the proportion of the diatom to phytoplankton community. However, the sediment record indicated that the eutrophication might actually have started from the end of the 20th century rather than the reported middle of 20th century. In contrast, biogenic elements in offshore sediment did not reflect disturbance by human activities. This study revealed that multi-nutrient proxies in sediment in the ECS could indicate natural environmental changes including runoff and the winter monsoon over the past century, as well as the influence of human activities in recent decades. Phosphorus species with distinct origins and biogeochemical behaviors could effectively reflect different aspects of past environmental conditions. [Copyright &y& Elsevier]

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]

Estuarine plankton communities can serve as indicators of ecosystem modification in response to anthropogenic influences. The main objectives of this study were to describe the spatial distribution and diurnal variability in zooplankton abundance and biomass over almost entire salinity gradient of the Changjiang (Yangtze) River estuary and to provide a background reference for future studies. To accomplish this, data were collected from 29 stations in the estuary from May 19 to 26, 2003, including two anchor stations. The spatial and diurnal variations in zooplankton characteristics, i.e. abundance, biomass, and gross taxonomic composition, were examined. Generally, both the abundance and biomass gradually increased seaward and presented distinct spatial variations. In addition, the spatial data revealed a significant correlation between abundance and biomass; however, there was no significant correlation between abundance and biomass for the diurnal data. Although the zooplankton composition indicated distinct spatial differences in terms of dominant groups, copepods accounted for >50% of the total zooplankton abundance in most regions and times. Three zooplankton assemblages were recognized through hierarchical cluster analysis. These assemblages existed along the salinity gradient from fresh water to seawater, and their positions coincided with those of the three principal water masses in the estuary. The assemblages were classified as: (1) true estuarine, (2) estuarine and marine, and (3) euryhaline marine, which were characterized by the copepods Sinocalanus dorrii, Labidocera euchaeta, and Calanus sinicus, respectively. Both spatial and diurnal data indicated that there was no significant correlation between zooplankton abundance/biomass and depth-integrated phytoplankton abundance. [ABSTRACT FROM AUTHOR]

Abstract: A geochemical study of Bohai Bay surface sediments was carried out to analyze the potential harmful element (PHE: Ge, Mo, In, Sn, Sb, Te, Tl, Bi and V) concentrations, transportation and deposition, enrichment factors and sources. Germanium, Mo, In, Sn, Sb, Te, Tl, Bi and V concentrations in the surface sediments were: 1.43–1.71, 0.52–1.43, 0.04–0.12, 2.77–4.14, 1.14–2.29, 0.027–0.085, 0.506–0.770, 0.27–0.63 and 70.35–115.90μg/g, respectively. The distributions of total PHE concentrations, together with sequential extraction analyses, showed that the PHEs were mainly due to natural inputs from the continental weathering delivered to the bay by rivers and atmospheric transportation and deposition. However, high Mo, Sb, Te, Bi and V occurred in non-residual fractions, suggesting some anthropogenic inputs in addition to the natural inputs. Besides sources, the distributions of PHEs were influenced by the coupling of physical, chemical and biological processes. Enrichment factor (EF) was computed for each site for each element in order to assess the polluting elements and the degree of pollution at each site. Results revealed that the EFs were generally lower than 1.0, particularly for Ge, Mo, In, Sn, Tl and V; however, the EFs were higher (>1.5), particularly for Sb, Te and Bi, revealing moderate contamination. [Copyright &y& Elsevier]

Abstract: We determined the selenite (Se(IV)) and selenate (Se(VI)) concentrations in the surface and bottom waters of Bohai Bay to understand the behavior of selenium in this area. The average concentrations of selenite and selenate were 0.72nM and 0.36nM, respectively. The surface concentration of selenite and selenate decreased from the western bay to the bay mouth, with the highest value near the Haihe Estuary. The bottom concentration of selenite and selenate displayed a similar distribution as the surface concentration. The selenium distribution was mainly controlled by environmental factors, riverine discharges and biological activities. Based on the data in this study, a preliminary estimate of the selenium budget via riverine input has been established. According to our estimate, about 7.18×107 mmol/yr of selenium reaches the Bohai Bay via rivers. Selenium showed significant positive correlations with dissolved inorganic nitrogen (DIN), phosphate and silicates, reflecting its strong nutrient-type behavior. The selenium concentration also correlated well with the chlorophyll a concentration and phytoplankton biomass, possibly implying that selenium plays a key role in regulating the phytoplankton productivity and that phytoplankton dynamics also affect the selenium inventory in Bohai Bay. Furthermore, the selenium concentration in each site was lower than the “no-effect” value of selenium and seemed to be required for the normal growth and development of phytoplankton, but it may have adverse effects for higher trophic levels due to the bioaccumulation of selenium. [Copyright &y& Elsevier]

Abstract: Water samples collected from Bohai Bay were determined to describe the distributions of lead, mercury, and copper in this area, indicating that mean values of the three metals were 1.63μg/L, 4.85×10−2 μg/L, and 2.68μg/L, respectively. Only lead exceeded the first class limit of seawater quality standard in China. Then, antioxidant enzymes, lipid peroxidation, and metabolic enzymes were investigated in bivalves (Chlamys farreri), exposed to three metals at the environmental concentration levels obtained from our investigation. Significantly reduced SOD, CAT and GPx activities, in lead-exposed group were observed and resulted in obvious lipid peroxidation. In contrast, mercury and copper did not show such clear oxidative stresses. In consistent with the oxidative stress variations, exposed only to lead caused a great inhibition on EROD activity. Multi-biomarker responses in bivalve when exposed to lead at the environmentally relevant concentration in Bohai Bay suggested that lead may possess a potential risk in this area. [Copyright &y& Elsevier]