The Agulhas Current is a major western boundary current flowing polewards on the southeast coast of South Africa.This analysis assesses its characteristics and suitability to generate power as a source of clean renewa...The Agulhas Current is a major western boundary current flowing polewards on the southeast coast of South Africa.This analysis assesses its characteristics and suitability to generate power as a source of clean renewable energy.On a section of coastline some 400 km long,over a period spanning more than 5 years an extensive set of current measurements was obtained.These data confirmed that south-westward currents with a speed greater than 1.2 m s^(-1)occurred over more than 60%of the recorded time;such ocean current speeds compare very favourably to winds required for energy generation.These currents occurred at the continental shelf break in water depths around 100 m,in the upper 50 m of the water column.Occasional current slowdowns and reversals did occur,with the major influence coming from‘Natal Pulses’,which are large-scale meanders in the Current that temporarily reversed the currents at the measurement sites.However,because of the surface temperature structure of the relevant water masses,such meanders can be identified in satellite imagery giving a few days advance warning of such current reversals.The characteristics of western boundary currents have been known for many years,but at Present,there is no operational system where this source of power is being utilised.It has tremendous potential for renewable energy generation,but is symptomatic of the many engineering challenges that still have to be solved to make such generation economically viable.展开更多
In November 1984,China launched its first expedition to the Southern Ocean and the Antarctic continent,culminating in the establishment of its first year-round research station—Great Wall Station—on the Antarctic Pe...In November 1984,China launched its first expedition to the Southern Ocean and the Antarctic continent,culminating in the establishment of its first year-round research station—Great Wall Station—on the Antarctic Peninsula in February 1985.Forty years later,in February 2024,China’s fifth research station,Qinling Station,commenced operations on Inexpress-ible Island near Terra Nova Bay.展开更多
Ecological floating bed is an important biological remediation method for water pollution control.During the removal of excess nutrients and pollutants,changes in environmental factors affect the characteristics of mi...Ecological floating bed is an important biological remediation method for water pollution control.During the removal of excess nutrients and pollutants,changes in environmental factors affect the characteristics of microorganisms in aquatic ecosystems.To understand the influences of ecological floating beds on size-fractionated microorganisms,we investigated the community assembly and nitrogen metabolic characteristics of three size-fractionated microorganism groups in the ecological floating bed area,using 18S rDNA,16S rDNA metabarcoding,and metagenomic sequencing techniques.Firstly,we discovered substantial differences between size-fractionated groups in the diversity and compositions of both microeukaryotic and bacterial communities,as well as the influences of floating beds on specific groups.The floating beds appeared to provide more habitats for heterotrophs and symbiotes while potentially inhibiting the growth of certain phytoplankton(cyanobacteria).Secondly,we observed that microeukaryotic and bacterial communities were predominantly influenced by stochastic and deterministic processes,respectively,and they both exhibited distinct patterns across different size-fractionated groups.Notably,microeukaryotic community assembly demonstrated a greater sensitivity to ecological floating beds,as indicated by an increase in dispersal limitation processes.Finally,the nitrogen metabolism functional genes revealed that microbes associated with large-sized particles played a crucial role in dissimilatory nitrate reduction to ammonium(DNRA)and denitrification processes within the floating bed area,thereby facilitating the removal of excess nitrogen nutrients from the water.In contrast,freeliving microorganisms from small-sized groups were linked mainly to the genes involved in nitrogen assimilation and assimilatory nitrate reduction to ammonium(ANRA)processes.These findings help understand the impact of ecological floating beds on the diversity and functional characteristics of microorganism communities in different size-fractionated groups.展开更多
Automated identification and tracking of mesoscale ocean eddies has recently become one research hotspot in physical oceanography. Several methods have been developed and applied to survey the general kinetic and geom...Automated identification and tracking of mesoscale ocean eddies has recently become one research hotspot in physical oceanography. Several methods have been developed and applied to survey the general kinetic and geometric characteristics of the ocean eddies in the South China Sea（SCS）. However, very few studies attempt to examine eddies＇ internal evolution processes. In this study, we reported a hybrid method to trace eddies＇ propagation in the SCS based on their internal structures, which are characterized by eddy centers, footprint borders, and composite borders. Eddy identification and tracking results were represented by a GIS-based spatiotemporal model. Information on instant states, dynamic evolution processes, and events of disappearance, reappearance, split, and mergence is stored in a GIS database. Results were validated by comparing against the ten Dongsha Cyclonic Eddies（DCEs） and the three long-lived anticyclonic eddies（ACEs） in the northern SCS, which were reported in previous literature. Our study confirmed the development of these eddies. Furthermore, we found more DCE-like and ACE-like eddies in these areas from 2005 to 2012 in our database. Spatial distribution analysis of disappearing, reappearing, splitting, and merging activities shows that eddies in the SCS tend to cluster to the northwest of Luzon Island, southwest of Luzon Strait, and around the marginal sea of Vietnam. Kuroshio intrusions and the complex sea floor topography in these areas are the possible factors that lead to these spatial clusters.展开更多
Spreading rate is a primary factor of mantle melting and tectonic behavior of the global mid-ocean ridges. The spreading rate of the Gakkel ridge decreases gradually from west to east. However, the Gakkel ridge can be...Spreading rate is a primary factor of mantle melting and tectonic behavior of the global mid-ocean ridges. The spreading rate of the Gakkel ridge decreases gradually from west to east. However, the Gakkel ridge can be divided into four thick-and-thin zones with varying crustal thicknesses along ridge axis. This phenomenon indicates that mantle melting of the Gakkel ridge is not a simple function of spreading rate. Mantle temperature, water content, mantle composition, and other factors are important in crustal accretion processes. Based on gravity-derived crustal thickness and wet melting model, we estimate that the mantle potential temperatures of the four zones are 1 270, 1 220, 1 280, and 1 280℃ （assuming that mantle water content equals to global average value）, with corresponding mantle water contents of 210, 0, 340, and 280 mg/kg （assuming that mantle potential temperature is 1 260℃）, respectivly. The western thinned crust zone is best modeled with low mantle temperature, whereas the other zones are mainly controlled by the enhanced conduction caused by the slower spreading rate. Along the Gakkel ridge, the crustal thickness is consistent with rock samples types. Predominated serpentinized peridotite and basalt are found in the area with crustal thickness 〈1.5 km and 〉2.5 km, respectively. The rock samples are including from basalt to peridotite in the area with crustal thickness between 1.5 and 2.5 km. Based on this consistency, the traditional magmatic accretion zone accounted for only 44% and amagmatic accretion accounted for 29% of the Gakkel ridge. The amagmatic accretion is a significant characteristic of the ultra-slow spreading ridge.展开更多
In the present paper, iodine （I）, iron （Fe）, manganese （Mn）, cobalt （Co）, phosphorus （P） and calcium （Ca） contents in three ferromanganese crusts from the Pacific Ocean are measured by spectrophotometric m...In the present paper, iodine （I）, iron （Fe）, manganese （Mn）, cobalt （Co）, phosphorus （P） and calcium （Ca） contents in three ferromanganese crusts from the Pacific Ocean are measured by spectrophotometric method and inductively coupled plasma atomic emission spectrometers （ICP-AES） to investigate the contents and distribution of iodine in ferromanganese crusts. The results show that iodine contents in three crusts vary between 27.1 and 836 mg/kg, with an average of 172 mg/kg, and the profile of iodine in the three crusts all exhibits a two-stage distribution zone： a young non-phosphatized zone and an old phosphatized zone that is rich in I, P and Ca. The iodine content ratios of old to young zone in MP5D44, CXD62-1 and CXD08-1 are 2.3, 3.4 and 13.7, respectively. The boundary depths of two-stage zone in MP5D44, CXD62-1 and CXD08-1 locate at 4.0 cm, 2.5 cm and 3.75 cm, respectively, and the time of iodine mutation in three crusts ranges from 17-37 Ma derived from 129I dating and Co empirical formula, which is consistent with the times of Cenozoic phosphatization events. The present study shows that the intensity of phosphatization is the main responsible for the distribution pattern of iodine in the crusts on the basis of the correlation analysis. Consequently, iodine is a sensitive indicator for phosphatization.展开更多
Nitrous oxide （N2O） distribution patterns in the Bering Sea basin （BSB） and Indian Sector of the Southern Ocean （ISSO） were described and compared. In both sites, the waters were divided into four layers： surfa...Nitrous oxide （N2O） distribution patterns in the Bering Sea basin （BSB） and Indian Sector of the Southern Ocean （ISSO） were described and compared. In both sites, the waters were divided into four layers： surface layer, subsurface layer, N2O maximum layer, and deep water. Simulations were made to find out the most important factors that regulate the N2O distribution patterns in different layers of both sites. The results showed that in the surface water, N2O was more understaturated in the ISSO than the BSB. This phenom- enon in the surface water of ISSO may result from ice melt water intrusion and northeastward transport of the Antarctic surface water. Results of the rough estimation of air-sea fluxes during the expedition were （-0.34±0.07）-（-0.64±0.13） μmol/（m2·d） and （-1.47±0.42）-（-1.77±0.51） μmol/（m-2·d） for the BSB and the ISSO, respectively. Strongly stratified surface layer and temperature minimum layer restricted exchange across the thermocline. The N2O maximum existed in higher concentration and deeper in the BSB than the ISSO, but their contribution to the upper layer by eddy diffusions was negligible. In deep waters, a concentration difference of 5 nmol/L N2O between these two sites was found, which suggested that N2O production occurred during thermohaline circulation. N2O may be a useful tracer to study important large-scale hydrographic processes.展开更多
Research and protection of biodiversity is generally started with species recognizing guided by achievement of cataloguing and illustration obtained through in situ investigation data accumulation and literature learn...Research and protection of biodiversity is generally started with species recognizing guided by achievement of cataloguing and illustration obtained through in situ investigation data accumulation and literature learning. Facing the shortage of taxonomist, it is getting harder to maintain important specimen collections and handle loans. The West Pacific Ocean has been operating as a center of the origin of global marine biodiversity result of the richest species diversity of marine taxa found in these waters. The present work is a compilation and summary of systematics, species diversity and new taxa of mesozooplankton major group known in West Pacific Ocean and its marginal seas （0°-45°N, 105°-152°E） according to 6 203 mesozooplankton samples acquired from 701 stations during 1965 and 2008. A total of 2 657 species belonging to 686 genera and 206 families of 10 mesozooplankton groups have been found through taxonomic identification and document consulting. In details, 697 species from 251 genera of 99 families belong to the Medusozoa, 59 species from 22 genera of 12 families to the Ctenophora, 85 species from 36 genera of 14 families to the pelagic Mollusca （Pteropoda and Heteropoda）, 416 species from 91 genera of 8 families to the Ostracoda, 908 species from 156 genera of 51 families to the Copepoda, 202 species from 60 genera of 4 families to the Mysidacea, 56 species from 8 genera of 2 families to the Euphausiacea, 105 species from 23 genera of 8 families to the Decapoda, 48 species from 13 genera of 5 families to the Chaetognatha and 81 species from 26 genera of 5 families to the Tunicata. The dominant species of each group are enumerated. Moreover, 2 new species of Medusozoa, Tubulariidae, Ectopleura, 1 new species of Medusozoa, Protiaridae, Halitiarella, 1 new genus and 1 new species of Medusozoa, Corymorphidae are established. An amount of 806 species are expanded with an increase of 43.5% on the basis of 1 852 species recorded before 2008, including 1.4% increase from tropical sea around equator, 4.0% from the frigid water in high latitude region, and 3.0% of bathypelagic-associated waters. The authors also summarized future prospects into five major areas in marine mesozooplankton research in China. Such information of qualitative phyletic classification could be of high relevance to studies on biodiversity and biogeography of marine mesozooplankton, especially for monographs contributed to make an overall and systematic conclusion on the species of marine life in China after 2008.展开更多
A bstract With the aim of elucidating the spatial and seasonal behaviors of rare earth elements(REEs), we investigated the dissolved REE concentrations of surface water collected during four seasons from middle, lower...A bstract With the aim of elucidating the spatial and seasonal behaviors of rare earth elements(REEs), we investigated the dissolved REE concentrations of surface water collected during four seasons from middle, lower reaches and estuary of the Minjiang River, southeastern China. The results display that the REE abundances in Minjiang River, ranging from 3.3–785.9 ng/L, were higher than those of many of the major global rivers. The total REE concentrations(∑REE) were seasonally variable, averaging in 5 937.30, 863.79, 825.65 and 1 065.75 ng/L during second highest flow(SHF), normal flow(NF), low flow(LF) and high flow(HF) season, respectively. The R_(( L/M)) and R_((H/M)) ratios reveal the spatial and temporal variations of REE patterns, and particularly vary apparently in the maximum turbidity zone and estuary. REE patterns of dissolved loads are characterized by progressing weaker LREEs-enrichment and stronger HREEsenrichment downstream from middle reaches to estuary during all four seasons. Comparing with NF and LF seasons, in which REE patterns are relatively flat, samples of SHF season have more LREE-enriched and HREE-depleted patterns that close to parent rocks, while samples of HF season are more LREEs-depleted and HREE-enriched. REE fractionations from the middle to lower reaches are stronger in the SHF and HF seasons than those in NF and LF seasons. Generally, spatial and seasonal variations in REE abundance and pattern are presumably due to several factors, such as chemical weathering, mixture with rainfall and groundwater, estuarine mixing, runoff, biological production and mountain river characters, such as strong hydrodynamic forces and steep slopes. The highest Gd/Gd* always occurs at north ports during all four seasons, where most of the large hospitals are located. This suggests Gd anomalies are depended on the density of modern medical facilities. Y/Ho ratios fl uctuate and positively correlate to salinity in estuary, probably because of the geochemical behavior differences between Y and Ho.展开更多
Over the past decades, the Arctic Ocean has experienced rapid warming under climate change, which has dramatically altered its physical and biogeochemical properties. Reduction in the sea-ice cover is one of the most ...Over the past decades, the Arctic Ocean has experienced rapid warming under climate change, which has dramatically altered its physical and biogeochemical properties. Reduction in the sea-ice cover is one of the most important driving forces of biogeochemical changes in the Arctic Ocean. Between 1999 and 2016, seven Chinese National Arctic Research Expeditions have taken place in the Bering and Chukchi seas, allowing assessment of the biogeochemical response of the western Arctic Ocean to global warming. Herein, we summarize advances in Chinese and international marine biogeochemistry research in the western Arctic Ocean, reviewing results from the Chinese expeditions and highlighting future trends of biogeochemistry in the Pacific Arctic region. The findings reported in this paper contribute towards a better understanding of water masses, greenhouse gases, nutrients, ocean acidification, and organic carbon export and burial processes in this region.展开更多
In the present study, we report N2 fixation rate(15N isotope tracer assay) and the diazotroph community structure(using the molecular method) in the western tropical North Pacific Ocean(WTNP)(13°–20°N, 120&...In the present study, we report N2 fixation rate(15N isotope tracer assay) and the diazotroph community structure(using the molecular method) in the western tropical North Pacific Ocean(WTNP)(13°–20°N, 120°–160°E). Our independent evidence on the basis of both in situ N2 fixation activity and diazotroph community structure showed the dominance of unicellular N2 fixation over majority of the WTNP surface waters during the sampling periods.Moreover, a shift in the diazotrophic composition from unicellular cyanobacteria group B-dominated to Trichodesmium spp.-dominated toward the western boundary current(Kuroshio) was also observed in 2013. We hypothesize that nutrient availability may have played a major role in regulating the biogeography of N2 fixation.In surface waters, volumetric N2 fixation rate(calculated by nitrogen) ranged between 0.6 and 2.6 nmol/(L·d) and averaged(1.2±0.5) nmol/(L·d), with <10 μm size fraction contributed predominantly(88%±6%) to the total rate between 135°E and 160°E. Depth-integrated N2 fixation rate over the upper 200 m ranged between 150 μmol/(m^2·d)and 480 μmol/(m^2·d)average(225±105) μmol/(m^2·d). N2 fixation can account for 6.2%±3.7% of the depthintegrated primary production, suggesting that N2 fixation is a significant N source sustaining new and export production in the WTNP. The role of N2 fixation in biogeochemical cycling in this climate change-vulnerable region calls for further investigations.展开更多
The submesoscale processes, including submesoscale eddies and fronts, have a strong vertical velocity, can thus make important supplements to the nutrients in the upper ocean. Using legacy multichannel seismic data AP...The submesoscale processes, including submesoscale eddies and fronts, have a strong vertical velocity, can thus make important supplements to the nutrients in the upper ocean. Using legacy multichannel seismic data AP25 of cruise EW9101 acquired northeast of the South Shetland Islands(Antarctic Peninsula) in February 1991, we identified an oceanic submesoscale eddy with the horizontal scale of ~4 km and a steep shelf break front that has variable dip angles from 5° to 10°. The submesoscale eddy is an anticyclonic eddy, which carries warm core water, can accelerate ice shelves melting. The upwelling induced by shelf break front may play an important role in transporting nutrients to the sea surface. The seismic images with very high lateral resolution may provide a new insight to understand the submesoscale and even small-scale oceanic phenomena in the interior.展开更多
Accurate and comprehensive knowledge of the atmospheric environment and its evolution within the coastal ocean boundary layer are necessary for understanding the sources,chemical mechanisms,and transport processes of ...Accurate and comprehensive knowledge of the atmospheric environment and its evolution within the coastal ocean boundary layer are necessary for understanding the sources,chemical mechanisms,and transport processes of air pollution in land,sea,and atmosphere.We present an overview of coastal ocean boundary layer detection technology and equipment in China and summarize the progress and main achievements in recent years.China has developed a series of coastal ocean boundary layer detection technologies,including Light Detection and Ranging(LIDAR),turbulent exchange analyzer,air-sea flux analyzer,stereoscopic remote sensing of air pollutants,and oceanic aerosol detection equipment to address the technical bottleneck caused by harsh environmental conditions in coastal ocean regions.Advances in these technologies and equipment have provided scientific assistance for addressing air pollution issues and understanding land-sea-atmosphere interactions over coastal ocean regions in China.In the future,routine atmospheric observations should cover the coastal ocean boundary layer of China.展开更多
Three specimens of the serranid fish(Serranidae), Plectranthias kamii Randall, 1980 were collected from fish market, Bitung, North Sulawesi on May and June 2010. Some morphological characters P. kamii is closely relat...Three specimens of the serranid fish(Serranidae), Plectranthias kamii Randall, 1980 were collected from fish market, Bitung, North Sulawesi on May and June 2010. Some morphological characters P. kamii is closely related to P. sheni, P. megalophthalmus, P. retrofasciatus, P. rubrifasciatus, P. knappi, P. helenae, P. pelicieri, P. jothyi, P.retrofasciatus and P. randalli in sharing of body width, upper jaw length, pelvic spine length and orbit diameter.Meristic count characters of P. kamii differ from P. sheni, P. pilicieri, P. megalophthalmus, P. retrofasciatus and P.rubrifasciatus in having more numerous dorsal spine(18 vs. 15–17) and below lateral line(33–34 vs. 29–33) and differ from P. megalophthalmus and P. rubrifasciatus in having more numerous pored scales in lateral line(13 vs.14–15) and shorter of anal spine. The present anthiine fish collected from Bitung, Indonesia was described as new record and bringing the total number of species of this genus known in Indonesia to seven.展开更多
In the open ocean,radium isotopes are useful tracers of residence time and water-mass mixing.However,limited by the measurement resolution of commonly used gamma counters,the low activity of radium in the open ocean m...In the open ocean,radium isotopes are useful tracers of residence time and water-mass mixing.However,limited by the measurement resolution of commonly used gamma counters,the low activity of radium in the open ocean makes it necessary to enrich radium from large volumes of seawater and pretreat radium-enriched carriers prior to measurements.The commonly applied method of radium enrichment and pretreatment,however,has limitations of uneven coating of MnO_(2)on cartridges,relatively expensive cartridges,time-consuming issues during cartridge-ashing,ash loss during transfer,and changes of gamma counters efficiency caused by different ash weights.To address these issues,in this study we optimized the enrichment and pretreatment of low-activity radium prior to measurements.Firstly,we replaced commonly used acrylic cartridges with cheaper polypropylene cartridges,which took 6 h to be ashed,42 h shorter than for acrylic cartridges.Secondly,MnO_(2)-coated cartridges were prepared with a circulating hot acidic KMnO_(4)solution to ensure homogeneous coating.The radium extraction efficiency of this MnO_(2)-coated cartridge was 20%-61%higher than that prepared by directly immersing cartridges in the solution.The radium delayed coincidence counter efficiency for MnO_(2)-coated cartridge was stable with a moisture content of 0.05-1.Lastly,after ashing cartridges,instead of directly transferring the ash to a measurement vial,a mixture of hydroxylamine hydrochloride and hydrochloric acid was used to completely leach the ash for long-lived radium,followed by coprecipitation by BaSO_(4),to avoid potential loss of ash during transfer and variations in measurement geometry due to different ash weights.And the recovery of long-lived radium pretreatment was 94%-102%,which improved by 11%compared with the common method.In addition,the radium extraction efficiency of the MnO_(2)-coated cartridge varied from 3%to 4%within the in situ pump working flow rate of 4-7 L/min,which fell within the measurement errors.展开更多
The establishment of effective proxies for the differentiation of sedimentary facies in the tide-dominated river mouth is fundamental to the delineation of stratigraphy and the study of paleoenvironments.Geochemical s...The establishment of effective proxies for the differentiation of sedimentary facies in the tide-dominated river mouth is fundamental to the delineation of stratigraphy and the study of paleoenvironments.Geochemical signatures of the acetic acid(HAc)extractive phases of alkaline earth metals,such as Sr,Ba,and Ca,are closely related to sedimentary environments and thus provide a novel method for discriminating the sedimentary facies of river mouth.In this study,50 surface water and surface sediment samples were obtained from different geomorphological units of the Jiulong River mouth,i.e.,river channel,distributary channel,delta front,delta front slope,prodelta,and shallow marine area,and the salinity of the water,the grain size,and the Sr,Ba,and Ca contents and Sr/Ba molar ratio(Sr/Ba)in HAc leachates of the sediments were determined.Contents of alkaline earth metals in HAc leachates of surface sediments from the Changjiang(Yangtze)River coast were also collated.The goals of this study were to reveal the spatial distribution of alkaline earth metals in the Jiulong River mouth,define their depositional mechanisms,and search for effective geochemical proxies for identification of the various sedimentary facies in the fluvial to marine transition zone.The results revealed several land-to-sea gradients.The Ba content decreased rapidly from the distributary channel to the sea,and the Sr and Ca contents and Sr/Ba increased gradually with the increase in salinity.Salinity,marine biomass,and sedimentary dynamic processes,were speculated to be the main reasons for the differences in their spatial distributions.There were significant differences in Ba,Sr,Ca,and Sr/Ba between the river channel and the distributary channel,in Ca and Ba between the distributary channel and the delta front(slope),and in Sr,Ca,and Sr/Ba between the delta front(slope)and the prodelta-shallow marine region.The Sr-Ba scatterplot showed that the sediments of the river channel and alluvial plain were located as a high Ba and low Sr element-defined end-member,whereas samples of the prodelta and shallow marine formed a high Sr and low Ba end-member.These can be used as characteristic end-members indicating terrestrial facies and marine facies,respectively.The sediments of the delta plain,tidal river,distributary channel,delta front,and delta front slope are located between these two end-member regions of the scatterplot,and this region of the diagram can be used to identify land-sea transitional sedimentary facies.展开更多
Dissolved organic carbon(DOC)constitutes the largest organic carbon reservoir in the ocean and plays a vital role in the oceanic carbon cycle.However,research on DOC in Antarctica has been limited,largely due to diffi...Dissolved organic carbon(DOC)constitutes the largest organic carbon reservoir in the ocean and plays a vital role in the oceanic carbon cycle.However,research on DOC in Antarctica has been limited,largely due to difficulties in sample collection.In this study,we investigate chromophoric dissolved organic matter(CDOM)in the Cosmonaut Sea and Cooperation Sea,Antarctica.The relative abundances of CDOM,as indicated by the absorption coefficient at 254 nm(a_(254)),exhibit significant variability,ranging from 1.29 m^(-1) to 8.37 m^(-1).The diatom species B is the primary contributor to CDOM in the region influenced by the Antarctic slope current.Using excitation-emission matrix fluorescence spectroscopy coupled with parallel factor analysis(EEM-PARAFAC),we identify three fluorescent components:one protein-like component(C1)and two humic-like components(C2 and C3).Our findings indicate that strong microbial activity in the euphotic zones of the Cosmonaut Sea and Cooperation Sea serves as a primary pathway for the removal of protein-like substances while also acting as a significant source of humic-like substances.Microbial degradation likely accounts for the decoupling of the vertical distribution of DOC and phytoplankton.Furthermore,the intrusion of modified circumpolar deep water(mCDW)into the euphotic zones of open ocean areas influences the distribution of CDOM at depths shallower than 200 m.These results have important implications for enhancing our understanding of the dynamics of CDOM and DOC in east Antarctica,as well as for improving assessments of the carbon cycle.展开更多
Microplastics(MPs)have recently emerged as a significant environmental problem with devastating consequences for organisms.Understanding MPs pollution in the Bay of Bengal is crucial for assessing its ecological impac...Microplastics(MPs)have recently emerged as a significant environmental problem with devastating consequences for organisms.Understanding MPs pollution in the Bay of Bengal is crucial for assessing its ecological impact on marine biodiversity and human health.This study examined the occurrence,spatial distribution,physical and chemical properties,ecological risks,and probable sources of MPs in estuarine and coastal marine environments in the northeastern Bay of Bengal.The average concentration of MPs in surface water of the Karnaphuli estuary,the Meghna estuary,and the southeastern coastal region were 916.7±462.6 items/m^(3),462.9±324.5 items/m^(3),and 350.0±190.5 items/m^(3),respectively,varying from 105.0±324.5 items/m^(3)to 1640.0±462.6 items/m^(3).In the sediments of the Karnaphuli estuary,the Meghna estuary,and the southeast coast of Bangladesh,the average amount of MPs were 94.3±33.1 items/kg,157.6±89.0 items/kg,and 134.3±38.7 items/kg,with a range of 60±33.1 items/kg to 334.3±89.0 items/kg.Most observed MPs were fibers(60.0%in the water;56.0%in the sediments),followed by fragments and lines.Detected MPs were dominated by polypropylene(20.7%)in the water,and acrylic(15.4%)in the sediment,black colored(76.2%in the water,72.7%in the sediments),and 200-500μm sized(48%in the water,37%in the sediments).Pollution Risk Index(PRI)indicated significant pollution levels(from medium to very high)in estuarine and coastal areas.Multi-statistical analysis indicated land-based inputs(tourists,local waste,agriculture,and industry)dominated the studied regions.The study emphasized the potential impact of MPs pollution on aquatic ecosystems,emphasizing the need for effective management,mitigation methods,continuous surveillance,and thorough evaluation.展开更多
Under the background of global climate change, anthropogenic processes have profoundly altered the sources and transport mechanisms of coastal sediments. While previous research has primarily focused on large river de...Under the background of global climate change, anthropogenic processes have profoundly altered the sources and transport mechanisms of coastal sediments. While previous research has primarily focused on large river delta coasts,the responses of the widely distributed small bays dominated by ocean dynamics, has received comparatively less attention. To address this gap, this study examines the Weihai Bay, located in the northeast of Shandong Peninsula,China. By integrating total organic carbon isotope tracers(δ^(13)C and C/N) with sediment transport modeling, we systematically analyze the spatiotemporal patterns of surface sediment grain size inside and outside the bay, along with their responses to natural and human-induced drivers. Our findings reveal that the sedimentary environment of Weihai Bay is governed by the combined effects of tidal currents, ocean currents, wave activity, and sediment supply. Tidal dynamics dominate the hydrodynamic conditions within the bay, while ocean currents predominate offshore. Surface sediments in the bay are primarily composed of silt, originating from sediments carried by the Yellow Sea Warm Current. These sediments enter the bay through the southern bay mouth under tidal forcing, are redistributed counterclockwise by residual tidal currents, and eventually exit via the northern bay mouth. Coarser sediments in specific areas are primarily controlled by strong wave action and terrestrial inputs. Between 1988 and 2023, Weihai Bay sediments have undergone a noticeable coarsening trend, primarily driven by anthropogenic modifications to sediment supply and hydrodynamic regimes. Coastal reclamation, shoreline modification, and infrastructure development have intensified coarse-grained terrestrial sediment input. Concurrently, shoreline advancement has reduced wave dissipation, enhancing nearshore hydrodynamics and accelerating sediment coarsening. This study highlights the sensitivity of small bay sedimentary environments to anthropogenic forcing, advancing our understanding of the coupled human-marine sediment system and providing a scientific basis for coastal sediment evolution under the dual influences of climate change and human activity.展开更多
Shallow-water seabed reverberation presents a critical disturbance in acoustic propagation,affecting the target detection performance of monostatic sonar.This paper proposes a novel seabed reverberation model integrat...Shallow-water seabed reverberation presents a critical disturbance in acoustic propagation,affecting the target detection performance of monostatic sonar.This paper proposes a novel seabed reverberation model integrating Gaussian beam tracing with seabed scattering physics.The model synthesizes time-domain reverberation signals by superimposing scattering signals received across multiple propagation paths.It accurately resolves scattering signals along distinct paths and enables simulation of reverberation under diverse shallow-water environments by adjusting the marine parameters.Furthermore,we model the seabed reverberation signals in the time domain and the space domain for a cylindrical transceiver array,and provide a detailed statistical characterization of the simulated seabed reverberation signals.Finally,shallow-water seabed reverberation experiments were conducted with a cylindrical transceiver array.Comparisons between shallow-water seabed reverberation measurements and simulation estimates at various sites and transceiver depths demonstrate that the proposed seabed reverberation model can efficiently simulate shallow-water seabed reverberation.展开更多
文摘The Agulhas Current is a major western boundary current flowing polewards on the southeast coast of South Africa.This analysis assesses its characteristics and suitability to generate power as a source of clean renewable energy.On a section of coastline some 400 km long,over a period spanning more than 5 years an extensive set of current measurements was obtained.These data confirmed that south-westward currents with a speed greater than 1.2 m s^(-1)occurred over more than 60%of the recorded time;such ocean current speeds compare very favourably to winds required for energy generation.These currents occurred at the continental shelf break in water depths around 100 m,in the upper 50 m of the water column.Occasional current slowdowns and reversals did occur,with the major influence coming from‘Natal Pulses’,which are large-scale meanders in the Current that temporarily reversed the currents at the measurement sites.However,because of the surface temperature structure of the relevant water masses,such meanders can be identified in satellite imagery giving a few days advance warning of such current reversals.The characteristics of western boundary currents have been known for many years,but at Present,there is no operational system where this source of power is being utilised.It has tremendous potential for renewable energy generation,but is symptomatic of the many engineering challenges that still have to be solved to make such generation economically viable.
文摘In November 1984,China launched its first expedition to the Southern Ocean and the Antarctic continent,culminating in the establishment of its first year-round research station—Great Wall Station—on the Antarctic Peninsula in February 1985.Forty years later,in February 2024,China’s fifth research station,Qinling Station,commenced operations on Inexpress-ible Island near Terra Nova Bay.
基金Supported by the National Natural Science Foundation of China(Nos.42141003,42176147)the National Key Research and Development Program of China(No.2022YFF0802204)the Xiamen Key Laboratory of Urban Sea Ecological Conservation and Restoration(USER)(Nos.USER2021-1,USER2021-5)。
文摘Ecological floating bed is an important biological remediation method for water pollution control.During the removal of excess nutrients and pollutants,changes in environmental factors affect the characteristics of microorganisms in aquatic ecosystems.To understand the influences of ecological floating beds on size-fractionated microorganisms,we investigated the community assembly and nitrogen metabolic characteristics of three size-fractionated microorganism groups in the ecological floating bed area,using 18S rDNA,16S rDNA metabarcoding,and metagenomic sequencing techniques.Firstly,we discovered substantial differences between size-fractionated groups in the diversity and compositions of both microeukaryotic and bacterial communities,as well as the influences of floating beds on specific groups.The floating beds appeared to provide more habitats for heterotrophs and symbiotes while potentially inhibiting the growth of certain phytoplankton(cyanobacteria).Secondly,we observed that microeukaryotic and bacterial communities were predominantly influenced by stochastic and deterministic processes,respectively,and they both exhibited distinct patterns across different size-fractionated groups.Notably,microeukaryotic community assembly demonstrated a greater sensitivity to ecological floating beds,as indicated by an increase in dispersal limitation processes.Finally,the nitrogen metabolism functional genes revealed that microbes associated with large-sized particles played a crucial role in dissimilatory nitrate reduction to ammonium(DNRA)and denitrification processes within the floating bed area,thereby facilitating the removal of excess nitrogen nutrients from the water.In contrast,freeliving microorganisms from small-sized groups were linked mainly to the genes involved in nitrogen assimilation and assimilatory nitrate reduction to ammonium(ANRA)processes.These findings help understand the impact of ecological floating beds on the diversity and functional characteristics of microorganism communities in different size-fractionated groups.
基金The National Science Foundation of China under contract Nos 41071250 and 41371378the Innovation Projects of the State Key Laboratory of Resource and Environment Information System,Chinese Academy of Sciences,under contract No.088RA500TA
文摘Automated identification and tracking of mesoscale ocean eddies has recently become one research hotspot in physical oceanography. Several methods have been developed and applied to survey the general kinetic and geometric characteristics of the ocean eddies in the South China Sea（SCS）. However, very few studies attempt to examine eddies＇ internal evolution processes. In this study, we reported a hybrid method to trace eddies＇ propagation in the SCS based on their internal structures, which are characterized by eddy centers, footprint borders, and composite borders. Eddy identification and tracking results were represented by a GIS-based spatiotemporal model. Information on instant states, dynamic evolution processes, and events of disappearance, reappearance, split, and mergence is stored in a GIS database. Results were validated by comparing against the ten Dongsha Cyclonic Eddies（DCEs） and the three long-lived anticyclonic eddies（ACEs） in the northern SCS, which were reported in previous literature. Our study confirmed the development of these eddies. Furthermore, we found more DCE-like and ACE-like eddies in these areas from 2005 to 2012 in our database. Spatial distribution analysis of disappearing, reappearing, splitting, and merging activities shows that eddies in the SCS tend to cluster to the northwest of Luzon Island, southwest of Luzon Strait, and around the marginal sea of Vietnam. Kuroshio intrusions and the complex sea floor topography in these areas are the possible factors that lead to these spatial clusters.
基金Chinese Polar Environment Comprehensive Investigation and Assessment Programmes under contract Nos CHINARE2013-03-03 and 2013-04-03the National Natural Science Foundation of China under contract No.41106049
文摘Spreading rate is a primary factor of mantle melting and tectonic behavior of the global mid-ocean ridges. The spreading rate of the Gakkel ridge decreases gradually from west to east. However, the Gakkel ridge can be divided into four thick-and-thin zones with varying crustal thicknesses along ridge axis. This phenomenon indicates that mantle melting of the Gakkel ridge is not a simple function of spreading rate. Mantle temperature, water content, mantle composition, and other factors are important in crustal accretion processes. Based on gravity-derived crustal thickness and wet melting model, we estimate that the mantle potential temperatures of the four zones are 1 270, 1 220, 1 280, and 1 280℃ （assuming that mantle water content equals to global average value）, with corresponding mantle water contents of 210, 0, 340, and 280 mg/kg （assuming that mantle potential temperature is 1 260℃）, respectivly. The western thinned crust zone is best modeled with low mantle temperature, whereas the other zones are mainly controlled by the enhanced conduction caused by the slower spreading rate. Along the Gakkel ridge, the crustal thickness is consistent with rock samples types. Predominated serpentinized peridotite and basalt are found in the area with crustal thickness 〈1.5 km and 〉2.5 km, respectively. The rock samples are including from basalt to peridotite in the area with crustal thickness between 1.5 and 2.5 km. Based on this consistency, the traditional magmatic accretion zone accounted for only 44% and amagmatic accretion accounted for 29% of the Gakkel ridge. The amagmatic accretion is a significant characteristic of the ultra-slow spreading ridge.
文摘In the present paper, iodine （I）, iron （Fe）, manganese （Mn）, cobalt （Co）, phosphorus （P） and calcium （Ca） contents in three ferromanganese crusts from the Pacific Ocean are measured by spectrophotometric method and inductively coupled plasma atomic emission spectrometers （ICP-AES） to investigate the contents and distribution of iodine in ferromanganese crusts. The results show that iodine contents in three crusts vary between 27.1 and 836 mg/kg, with an average of 172 mg/kg, and the profile of iodine in the three crusts all exhibits a two-stage distribution zone： a young non-phosphatized zone and an old phosphatized zone that is rich in I, P and Ca. The iodine content ratios of old to young zone in MP5D44, CXD62-1 and CXD08-1 are 2.3, 3.4 and 13.7, respectively. The boundary depths of two-stage zone in MP5D44, CXD62-1 and CXD08-1 locate at 4.0 cm, 2.5 cm and 3.75 cm, respectively, and the time of iodine mutation in three crusts ranges from 17-37 Ma derived from 129I dating and Co empirical formula, which is consistent with the times of Cenozoic phosphatization events. The present study shows that the intensity of phosphatization is the main responsible for the distribution pattern of iodine in the crusts on the basis of the correlation analysis. Consequently, iodine is a sensitive indicator for phosphatization.
基金The National Natural Science Foundation of China(NSFC)under contract Nos 40906102 and 41230529the CHINARE under contract Nos 2012-2015(-01-04-02),2012-2015(01-02-01)and 2012-2015(03-04-02)the CAA International Cooperation Projects under contract Nos IC201201 and IC201308
文摘Nitrous oxide （N2O） distribution patterns in the Bering Sea basin （BSB） and Indian Sector of the Southern Ocean （ISSO） were described and compared. In both sites, the waters were divided into four layers： surface layer, subsurface layer, N2O maximum layer, and deep water. Simulations were made to find out the most important factors that regulate the N2O distribution patterns in different layers of both sites. The results showed that in the surface water, N2O was more understaturated in the ISSO than the BSB. This phenom- enon in the surface water of ISSO may result from ice melt water intrusion and northeastward transport of the Antarctic surface water. Results of the rough estimation of air-sea fluxes during the expedition were （-0.34±0.07）-（-0.64±0.13） μmol/（m2·d） and （-1.47±0.42）-（-1.77±0.51） μmol/（m-2·d） for the BSB and the ISSO, respectively. Strongly stratified surface layer and temperature minimum layer restricted exchange across the thermocline. The N2O maximum existed in higher concentration and deeper in the BSB than the ISSO, but their contribution to the upper layer by eddy diffusions was negligible. In deep waters, a concentration difference of 5 nmol/L N2O between these two sites was found, which suggested that N2O production occurred during thermohaline circulation. N2O may be a useful tracer to study important large-scale hydrographic processes.
基金The National Natural Science Foundation of China under contract Nos 41506217 and 41506136the Basic Research of the National Department of Science and Technology under contract Nos GASI-01-02-04 and 201105022-2
文摘Research and protection of biodiversity is generally started with species recognizing guided by achievement of cataloguing and illustration obtained through in situ investigation data accumulation and literature learning. Facing the shortage of taxonomist, it is getting harder to maintain important specimen collections and handle loans. The West Pacific Ocean has been operating as a center of the origin of global marine biodiversity result of the richest species diversity of marine taxa found in these waters. The present work is a compilation and summary of systematics, species diversity and new taxa of mesozooplankton major group known in West Pacific Ocean and its marginal seas （0°-45°N, 105°-152°E） according to 6 203 mesozooplankton samples acquired from 701 stations during 1965 and 2008. A total of 2 657 species belonging to 686 genera and 206 families of 10 mesozooplankton groups have been found through taxonomic identification and document consulting. In details, 697 species from 251 genera of 99 families belong to the Medusozoa, 59 species from 22 genera of 12 families to the Ctenophora, 85 species from 36 genera of 14 families to the pelagic Mollusca （Pteropoda and Heteropoda）, 416 species from 91 genera of 8 families to the Ostracoda, 908 species from 156 genera of 51 families to the Copepoda, 202 species from 60 genera of 4 families to the Mysidacea, 56 species from 8 genera of 2 families to the Euphausiacea, 105 species from 23 genera of 8 families to the Decapoda, 48 species from 13 genera of 5 families to the Chaetognatha and 81 species from 26 genera of 5 families to the Tunicata. The dominant species of each group are enumerated. Moreover, 2 new species of Medusozoa, Tubulariidae, Ectopleura, 1 new species of Medusozoa, Protiaridae, Halitiarella, 1 new genus and 1 new species of Medusozoa, Corymorphidae are established. An amount of 806 species are expanded with an increase of 43.5% on the basis of 1 852 species recorded before 2008, including 1.4% increase from tropical sea around equator, 4.0% from the frigid water in high latitude region, and 3.0% of bathypelagic-associated waters. The authors also summarized future prospects into five major areas in marine mesozooplankton research in China. Such information of qualitative phyletic classification could be of high relevance to studies on biodiversity and biogeography of marine mesozooplankton, especially for monographs contributed to make an overall and systematic conclusion on the species of marine life in China after 2008.
基金Supported by the National Natural Science Foundation of China(No.41376050)
文摘A bstract With the aim of elucidating the spatial and seasonal behaviors of rare earth elements(REEs), we investigated the dissolved REE concentrations of surface water collected during four seasons from middle, lower reaches and estuary of the Minjiang River, southeastern China. The results display that the REE abundances in Minjiang River, ranging from 3.3–785.9 ng/L, were higher than those of many of the major global rivers. The total REE concentrations(∑REE) were seasonally variable, averaging in 5 937.30, 863.79, 825.65 and 1 065.75 ng/L during second highest flow(SHF), normal flow(NF), low flow(LF) and high flow(HF) season, respectively. The R_(( L/M)) and R_((H/M)) ratios reveal the spatial and temporal variations of REE patterns, and particularly vary apparently in the maximum turbidity zone and estuary. REE patterns of dissolved loads are characterized by progressing weaker LREEs-enrichment and stronger HREEsenrichment downstream from middle reaches to estuary during all four seasons. Comparing with NF and LF seasons, in which REE patterns are relatively flat, samples of SHF season have more LREE-enriched and HREE-depleted patterns that close to parent rocks, while samples of HF season are more LREEs-depleted and HREE-enriched. REE fractionations from the middle to lower reaches are stronger in the SHF and HF seasons than those in NF and LF seasons. Generally, spatial and seasonal variations in REE abundance and pattern are presumably due to several factors, such as chemical weathering, mixture with rainfall and groundwater, estuarine mixing, runoff, biological production and mountain river characters, such as strong hydrodynamic forces and steep slopes. The highest Gd/Gd* always occurs at north ports during all four seasons, where most of the large hospitals are located. This suggests Gd anomalies are depended on the density of modern medical facilities. Y/Ho ratios fl uctuate and positively correlate to salinity in estuary, probably because of the geochemical behavior differences between Y and Ho.
基金the National Natural Science Foundation of China (Grant nos. 41506222, 41776205, 41606052, 41606211)Chinese Polar Environment Comprehensive Investigation & Assessment Programs (Grant nos. CHINARE2017-03-04, 2017-04-03)the Fundamental Research Funds for the Second Institute of Oceanography, SOA (Grant nos. JG1611, JG1502)
文摘Over the past decades, the Arctic Ocean has experienced rapid warming under climate change, which has dramatically altered its physical and biogeochemical properties. Reduction in the sea-ice cover is one of the most important driving forces of biogeochemical changes in the Arctic Ocean. Between 1999 and 2016, seven Chinese National Arctic Research Expeditions have taken place in the Bering and Chukchi seas, allowing assessment of the biogeochemical response of the western Arctic Ocean to global warming. Herein, we summarize advances in Chinese and international marine biogeochemistry research in the western Arctic Ocean, reviewing results from the Chinese expeditions and highlighting future trends of biogeochemistry in the Pacific Arctic region. The findings reported in this paper contribute towards a better understanding of water masses, greenhouse gases, nutrients, ocean acidification, and organic carbon export and burial processes in this region.
基金The National Basic Research Program of China under contract No.2015CB452903the Foundation of China Ocean Mineral Resources R&D Association under contract No.DY135-E2-2-03+1 种基金the Science and Technology Basic Resources Investigation Program of China under contract No.2017FY201403the National Natural Science Foundation of China under contract Nos 41676174,41206104 and 41876198
文摘In the present study, we report N2 fixation rate(15N isotope tracer assay) and the diazotroph community structure(using the molecular method) in the western tropical North Pacific Ocean(WTNP)(13°–20°N, 120°–160°E). Our independent evidence on the basis of both in situ N2 fixation activity and diazotroph community structure showed the dominance of unicellular N2 fixation over majority of the WTNP surface waters during the sampling periods.Moreover, a shift in the diazotrophic composition from unicellular cyanobacteria group B-dominated to Trichodesmium spp.-dominated toward the western boundary current(Kuroshio) was also observed in 2013. We hypothesize that nutrient availability may have played a major role in regulating the biogeography of N2 fixation.In surface waters, volumetric N2 fixation rate(calculated by nitrogen) ranged between 0.6 and 2.6 nmol/(L·d) and averaged(1.2±0.5) nmol/(L·d), with <10 μm size fraction contributed predominantly(88%±6%) to the total rate between 135°E and 160°E. Depth-integrated N2 fixation rate over the upper 200 m ranged between 150 μmol/(m^2·d)and 480 μmol/(m^2·d)average(225±105) μmol/(m^2·d). N2 fixation can account for 6.2%±3.7% of the depthintegrated primary production, suggesting that N2 fixation is a significant N source sustaining new and export production in the WTNP. The role of N2 fixation in biogeochemical cycling in this climate change-vulnerable region calls for further investigations.
基金financially supported by National Polar Special Program “Impact and Response of Antarctic Seas to Climate Change” (Grant nos. IRASCC 01-03-01, 01-03-02)funded by the National Natural Science Foundation of China (Grant no. 41976048)the National Key R&D Program of China (Grant no. 2018YFC0310000)。
文摘The submesoscale processes, including submesoscale eddies and fronts, have a strong vertical velocity, can thus make important supplements to the nutrients in the upper ocean. Using legacy multichannel seismic data AP25 of cruise EW9101 acquired northeast of the South Shetland Islands(Antarctic Peninsula) in February 1991, we identified an oceanic submesoscale eddy with the horizontal scale of ~4 km and a steep shelf break front that has variable dip angles from 5° to 10°. The submesoscale eddy is an anticyclonic eddy, which carries warm core water, can accelerate ice shelves melting. The upwelling induced by shelf break front may play an important role in transporting nutrients to the sea surface. The seismic images with very high lateral resolution may provide a new insight to understand the submesoscale and even small-scale oceanic phenomena in the interior.
基金supported by the National Key Research and Development Program of China(Nos.2018YFC0213106,2018YFC0213101,2018YFC0213102,2018YFC0213103,2018YFC0213104 and 2018YFC0213105)Anhui Provincial Natural Science Foundation(No.2108085QD177)the CASHIPS Director’s Fund(No.YZJJ2021QN07)。
文摘Accurate and comprehensive knowledge of the atmospheric environment and its evolution within the coastal ocean boundary layer are necessary for understanding the sources,chemical mechanisms,and transport processes of air pollution in land,sea,and atmosphere.We present an overview of coastal ocean boundary layer detection technology and equipment in China and summarize the progress and main achievements in recent years.China has developed a series of coastal ocean boundary layer detection technologies,including Light Detection and Ranging(LIDAR),turbulent exchange analyzer,air-sea flux analyzer,stereoscopic remote sensing of air pollutants,and oceanic aerosol detection equipment to address the technical bottleneck caused by harsh environmental conditions in coastal ocean regions.Advances in these technologies and equipment have provided scientific assistance for addressing air pollution issues and understanding land-sea-atmosphere interactions over coastal ocean regions in China.In the future,routine atmospheric observations should cover the coastal ocean boundary layer of China.
基金The Biodiversity Program of Kema and Amurang,Bitung Marine Life Conservation,Research Center for Oceanography,Indonesian Institute of Sciences,Indonesiathe China-Indonesia Maritime Cooperation Fund Project "ChinaIndonesia Bitung Ecological Station Establishment"
文摘Three specimens of the serranid fish(Serranidae), Plectranthias kamii Randall, 1980 were collected from fish market, Bitung, North Sulawesi on May and June 2010. Some morphological characters P. kamii is closely related to P. sheni, P. megalophthalmus, P. retrofasciatus, P. rubrifasciatus, P. knappi, P. helenae, P. pelicieri, P. jothyi, P.retrofasciatus and P. randalli in sharing of body width, upper jaw length, pelvic spine length and orbit diameter.Meristic count characters of P. kamii differ from P. sheni, P. pilicieri, P. megalophthalmus, P. retrofasciatus and P.rubrifasciatus in having more numerous dorsal spine(18 vs. 15–17) and below lateral line(33–34 vs. 29–33) and differ from P. megalophthalmus and P. rubrifasciatus in having more numerous pored scales in lateral line(13 vs.14–15) and shorter of anal spine. The present anthiine fish collected from Bitung, Indonesia was described as new record and bringing the total number of species of this genus known in Indonesia to seven.
基金The National Natural Science Foundation of China under contract No.41576074the Natural Science Foundation of Fujian Province of China under contract No.2019J01020.
文摘In the open ocean,radium isotopes are useful tracers of residence time and water-mass mixing.However,limited by the measurement resolution of commonly used gamma counters,the low activity of radium in the open ocean makes it necessary to enrich radium from large volumes of seawater and pretreat radium-enriched carriers prior to measurements.The commonly applied method of radium enrichment and pretreatment,however,has limitations of uneven coating of MnO_(2)on cartridges,relatively expensive cartridges,time-consuming issues during cartridge-ashing,ash loss during transfer,and changes of gamma counters efficiency caused by different ash weights.To address these issues,in this study we optimized the enrichment and pretreatment of low-activity radium prior to measurements.Firstly,we replaced commonly used acrylic cartridges with cheaper polypropylene cartridges,which took 6 h to be ashed,42 h shorter than for acrylic cartridges.Secondly,MnO_(2)-coated cartridges were prepared with a circulating hot acidic KMnO_(4)solution to ensure homogeneous coating.The radium extraction efficiency of this MnO_(2)-coated cartridge was 20%-61%higher than that prepared by directly immersing cartridges in the solution.The radium delayed coincidence counter efficiency for MnO_(2)-coated cartridge was stable with a moisture content of 0.05-1.Lastly,after ashing cartridges,instead of directly transferring the ash to a measurement vial,a mixture of hydroxylamine hydrochloride and hydrochloric acid was used to completely leach the ash for long-lived radium,followed by coprecipitation by BaSO_(4),to avoid potential loss of ash during transfer and variations in measurement geometry due to different ash weights.And the recovery of long-lived radium pretreatment was 94%-102%,which improved by 11%compared with the common method.In addition,the radium extraction efficiency of the MnO_(2)-coated cartridge varied from 3%to 4%within the in situ pump working flow rate of 4-7 L/min,which fell within the measurement errors.
基金The National Natural Science Foundation of China under contract Nos 42476156,41961144022the Natural Science Foundation of Fujian Province,China under contract No.2023J01927+1 种基金the College Students’Innovation and Entrepreneurship Training Program of Fujian Province,China under contract No.S202310402032the Scientific Research Foundation of the Third Institute of Oceanography,SOA,China under contract No.2019018。
文摘The establishment of effective proxies for the differentiation of sedimentary facies in the tide-dominated river mouth is fundamental to the delineation of stratigraphy and the study of paleoenvironments.Geochemical signatures of the acetic acid(HAc)extractive phases of alkaline earth metals,such as Sr,Ba,and Ca,are closely related to sedimentary environments and thus provide a novel method for discriminating the sedimentary facies of river mouth.In this study,50 surface water and surface sediment samples were obtained from different geomorphological units of the Jiulong River mouth,i.e.,river channel,distributary channel,delta front,delta front slope,prodelta,and shallow marine area,and the salinity of the water,the grain size,and the Sr,Ba,and Ca contents and Sr/Ba molar ratio(Sr/Ba)in HAc leachates of the sediments were determined.Contents of alkaline earth metals in HAc leachates of surface sediments from the Changjiang(Yangtze)River coast were also collated.The goals of this study were to reveal the spatial distribution of alkaline earth metals in the Jiulong River mouth,define their depositional mechanisms,and search for effective geochemical proxies for identification of the various sedimentary facies in the fluvial to marine transition zone.The results revealed several land-to-sea gradients.The Ba content decreased rapidly from the distributary channel to the sea,and the Sr and Ca contents and Sr/Ba increased gradually with the increase in salinity.Salinity,marine biomass,and sedimentary dynamic processes,were speculated to be the main reasons for the differences in their spatial distributions.There were significant differences in Ba,Sr,Ca,and Sr/Ba between the river channel and the distributary channel,in Ca and Ba between the distributary channel and the delta front(slope),and in Sr,Ca,and Sr/Ba between the delta front(slope)and the prodelta-shallow marine region.The Sr-Ba scatterplot showed that the sediments of the river channel and alluvial plain were located as a high Ba and low Sr element-defined end-member,whereas samples of the prodelta and shallow marine formed a high Sr and low Ba end-member.These can be used as characteristic end-members indicating terrestrial facies and marine facies,respectively.The sediments of the delta plain,tidal river,distributary channel,delta front,and delta front slope are located between these two end-member regions of the scatterplot,and this region of the diagram can be used to identify land-sea transitional sedimentary facies.
基金The National Natural Science Foundation of China under contract Nos 42276255,41976228,42176227 and 42306262the National Polar Special Program under contract Nos IRASCC 01-01-02,IRASCC 02-02-03,and IRASCC 02-02-05the Scientific Research Fund of the Second Institute of Oceanography under contract Nos JG2211 and JG2212.
文摘Dissolved organic carbon(DOC)constitutes the largest organic carbon reservoir in the ocean and plays a vital role in the oceanic carbon cycle.However,research on DOC in Antarctica has been limited,largely due to difficulties in sample collection.In this study,we investigate chromophoric dissolved organic matter(CDOM)in the Cosmonaut Sea and Cooperation Sea,Antarctica.The relative abundances of CDOM,as indicated by the absorption coefficient at 254 nm(a_(254)),exhibit significant variability,ranging from 1.29 m^(-1) to 8.37 m^(-1).The diatom species B is the primary contributor to CDOM in the region influenced by the Antarctic slope current.Using excitation-emission matrix fluorescence spectroscopy coupled with parallel factor analysis(EEM-PARAFAC),we identify three fluorescent components:one protein-like component(C1)and two humic-like components(C2 and C3).Our findings indicate that strong microbial activity in the euphotic zones of the Cosmonaut Sea and Cooperation Sea serves as a primary pathway for the removal of protein-like substances while also acting as a significant source of humic-like substances.Microbial degradation likely accounts for the decoupling of the vertical distribution of DOC and phytoplankton.Furthermore,the intrusion of modified circumpolar deep water(mCDW)into the euphotic zones of open ocean areas influences the distribution of CDOM at depths shallower than 200 m.These results have important implications for enhancing our understanding of the dynamics of CDOM and DOC in east Antarctica,as well as for improving assessments of the carbon cycle.
基金Supported by the National Natural Science Foundation of China(NSFC)Shared Voyage Project(Nos.41776088,41976018,42049911,U20A20103,U2005207)the Natural Science Key Foundation of Fujian Province,China(No.2020J01412103)+5 种基金the Hainan Province Science and Technology Special Fund(No.ZDYF2022SHFZ317)the Guangxi Talent and Innovation Base Project(No.2018AD19280)the Guangxi Funding Project(No.04024XM20N0006)the Beihai Science&Technology Project(Nos.201995037,202082031,202082022)the Natural Science Foundation of Xiamen City of China(No.502Z20227322)the China Scholarship Council(CSC Marine Scholarship)。
文摘Microplastics(MPs)have recently emerged as a significant environmental problem with devastating consequences for organisms.Understanding MPs pollution in the Bay of Bengal is crucial for assessing its ecological impact on marine biodiversity and human health.This study examined the occurrence,spatial distribution,physical and chemical properties,ecological risks,and probable sources of MPs in estuarine and coastal marine environments in the northeastern Bay of Bengal.The average concentration of MPs in surface water of the Karnaphuli estuary,the Meghna estuary,and the southeastern coastal region were 916.7±462.6 items/m^(3),462.9±324.5 items/m^(3),and 350.0±190.5 items/m^(3),respectively,varying from 105.0±324.5 items/m^(3)to 1640.0±462.6 items/m^(3).In the sediments of the Karnaphuli estuary,the Meghna estuary,and the southeast coast of Bangladesh,the average amount of MPs were 94.3±33.1 items/kg,157.6±89.0 items/kg,and 134.3±38.7 items/kg,with a range of 60±33.1 items/kg to 334.3±89.0 items/kg.Most observed MPs were fibers(60.0%in the water;56.0%in the sediments),followed by fragments and lines.Detected MPs were dominated by polypropylene(20.7%)in the water,and acrylic(15.4%)in the sediment,black colored(76.2%in the water,72.7%in the sediments),and 200-500μm sized(48%in the water,37%in the sediments).Pollution Risk Index(PRI)indicated significant pollution levels(from medium to very high)in estuarine and coastal areas.Multi-statistical analysis indicated land-based inputs(tourists,local waste,agriculture,and industry)dominated the studied regions.The study emphasized the potential impact of MPs pollution on aquatic ecosystems,emphasizing the need for effective management,mitigation methods,continuous surveillance,and thorough evaluation.
基金The Fund of National Archaeological Talent Promotion Program of China under contract No.2024-269“2024 Shandong Weihai Underwater Archaeological Survey” program by National Center for Archaeology under contract No. 20243160A0965+2 种基金Fujian Provincial Science and Technology Planning Projects under contract No. 2022L3001Provincial Natural Science Foundation of Fujian under contract No. 2023J01020MEL Internal Program of Xiamen University under contract No. MELRI2303。
文摘Under the background of global climate change, anthropogenic processes have profoundly altered the sources and transport mechanisms of coastal sediments. While previous research has primarily focused on large river delta coasts,the responses of the widely distributed small bays dominated by ocean dynamics, has received comparatively less attention. To address this gap, this study examines the Weihai Bay, located in the northeast of Shandong Peninsula,China. By integrating total organic carbon isotope tracers(δ^(13)C and C/N) with sediment transport modeling, we systematically analyze the spatiotemporal patterns of surface sediment grain size inside and outside the bay, along with their responses to natural and human-induced drivers. Our findings reveal that the sedimentary environment of Weihai Bay is governed by the combined effects of tidal currents, ocean currents, wave activity, and sediment supply. Tidal dynamics dominate the hydrodynamic conditions within the bay, while ocean currents predominate offshore. Surface sediments in the bay are primarily composed of silt, originating from sediments carried by the Yellow Sea Warm Current. These sediments enter the bay through the southern bay mouth under tidal forcing, are redistributed counterclockwise by residual tidal currents, and eventually exit via the northern bay mouth. Coarser sediments in specific areas are primarily controlled by strong wave action and terrestrial inputs. Between 1988 and 2023, Weihai Bay sediments have undergone a noticeable coarsening trend, primarily driven by anthropogenic modifications to sediment supply and hydrodynamic regimes. Coastal reclamation, shoreline modification, and infrastructure development have intensified coarse-grained terrestrial sediment input. Concurrently, shoreline advancement has reduced wave dissipation, enhancing nearshore hydrodynamics and accelerating sediment coarsening. This study highlights the sensitivity of small bay sedimentary environments to anthropogenic forcing, advancing our understanding of the coupled human-marine sediment system and providing a scientific basis for coastal sediment evolution under the dual influences of climate change and human activity.
基金The Youth Project of National Natural Science Foundation of China under contract No.12304507the Natural Science Foundation of Guangdong Province,China under contract No.2024A1515011512+2 种基金the Stable Supporting Fund of Acoustic Science and Technology Laboratory under contract No.JCKYS2025SSJS010the Fundamental Research Funds for the Central Universities under contract No.20720240108the Special Project for Marine Economy Development of Guangdong Province,China under contract No.GDNRC2023-47.
文摘Shallow-water seabed reverberation presents a critical disturbance in acoustic propagation,affecting the target detection performance of monostatic sonar.This paper proposes a novel seabed reverberation model integrating Gaussian beam tracing with seabed scattering physics.The model synthesizes time-domain reverberation signals by superimposing scattering signals received across multiple propagation paths.It accurately resolves scattering signals along distinct paths and enables simulation of reverberation under diverse shallow-water environments by adjusting the marine parameters.Furthermore,we model the seabed reverberation signals in the time domain and the space domain for a cylindrical transceiver array,and provide a detailed statistical characterization of the simulated seabed reverberation signals.Finally,shallow-water seabed reverberation experiments were conducted with a cylindrical transceiver array.Comparisons between shallow-water seabed reverberation measurements and simulation estimates at various sites and transceiver depths demonstrate that the proposed seabed reverberation model can efficiently simulate shallow-water seabed reverberation.
