Volume articles

The backscattering coefficient of particles is one of the most important inherent optical parameters of water body, and also is the core parameter of ocean color remote sensing. It is very important to measure the backscattering coefficient data of particles in water accurately in-situ for the construction of water color remote sensing model and the authenticity test of water color remote sensing products. In this study, the consistency of these three kinds of in-situ instruments(HydroScat6, VSF3 and BB9) for measuring backscattering coefficient of water particles were compared and analyzed. The results show that the measurements by these three kinds of instruments have good consistency in clean water, but in the turbid water, the measurements of HydroScat6 and BB9 are higher than those of VSF3, and their deviations are significantly increased. Based on numerical simulations and laboratory measurements, it is found that the shapes of particles affect the consistency of measurements by the three instruments, and the consistency is better for spherical particles than that of field particles.

Ocean chlorophyll- a concentration remote sensing product is important data sources for the studies of ocean primary productivity and carbon sequestration capacity of ocean ecosystems. In order to ensure the data reliability, it is particularly important to verify the accuracy of remote sensing product and analyze the causes of validation errors. In the verification of remote sensing products, due to the existence of spatial variation, the measured data within the remote sensing pixel have different statistical distribution characteristics, and thus produce different statistical error results. In this work, chlorophyll- a concentration remote sensing products derived from MODIS-Aqua, MODIS-Terra, MERIS and SeaWiFS satellite sensors, were quantitatively analyzed on the relationship between spatial variability and validation accuracy. The results of statistical analysis show that spatial variation is one of the direct causes of validation error. The relationship between Mean Absolute Percentage Error ( MAPE) and spatial Coefficient of Variation ( CV) is in accordance with power exponential model. When CV<0.05, MAPE increases significantly with CV, and when CV>0.15, MAPE changes gently. The validation results of different chlorophyll- a concentration remote sensing products show that SeaWiFS has the highest accuracy, MERIS takes the second place, and MODIS-Terra has the worst accuracy.

The use of remote sensing technology to quickly extract the shorelines of islands is an important technology. An approach of marked watershed based on extended extremum transform was proposed in this study, solving the problems of over-segmentation and poor anti-interference ability of traditional watershed algorithm in high-resolution multispectral satellite data processing. Firstly, the foreground and background markers were established by morphological reconstruction and extended extremum transform to suppress the minimum and maximum gray regions initially, then the gradient image was modified based on above markers, and finally the island shoreline was extracted based on the improved watershed transform method. The typical islands located in the South China Sea region were selected, and the accuracy and reliability of the proposed method were verified using 2017 GF-2 satellite data. The results show that the accuracy of artificial shorelines is higher than 90% within 1 pixel(4 m) for island shorelines, and the accuracy of sandy shorelines is higher than 90% within 1.5 pixels(6 m), confirmed that the proposed method can be used for segmentation of high-resolution multispectral images and extraction of island shoreline.

The underwater glider is an important platform for unmanned motion observation of the ocean. However, it is difficult to maintain the preset net array when multiple underwater gliders cooperate in observation.In this study, an underwater glider group cooperative control algorithm based on Newton mechanical integration was proposed to adjust the motion parameters of the glider group before entering the water according to its asynchronous entering and leaving the water.Based on the force analysis of the underwater glider, the motion state of the underwater glider in the ocean was restored by Newton mechanics integral. The cooperative control algorithm of the underwater glider group was used to constrain the motion of several underwater gliders at the same time, and the simulation experiment was carried out. The results of experiment show that the algorithm can keep the preset net array of multiple underwater gliders well, so that the target sea area can be observed cooperatively.

Aiming at the requirements of the mobile ocean seismograph for high reliability and low power consumption of the control system, a hardware circuit design scheme based on the Cortex-M4 core was proposed. Firstly, the ultra-low-power consumption STM32L4 was selected as the MCU(Microprogrammed Control Unit) to ensure high operating capacity and reduce power consumption; secondly, a targeted two-level voltage reduction scheme was proposed for the ultra-low-power modules, such as MCU and sensor system, to greatly improve the power conversion efficiency of the circuit and a suitable buck chips was selected for the high-power modules such as buoyancy adjustment systems and communication systems to ensure circuit safety and improve the conversion efficiency. Finally, the peripheral circuit was filtered and protected. The reliability of the different modules was verified through tests which prove that the hardware circuit can support the seismograph to achieve the complete observation task and the circuit design is highly reliable.

Based on historical topographic maps, charts and remote sensing images since 1913, 10 periods of coastline data covering Sanmen Bay were obtained and analyzed using GIS and spatial analysis tools. The temporal and spatial evolution characteristics of the coastlines in Sanmen Bay during the last 100 years were investigated. The results show that: (1) The changes of coastlines mainly occurred in the inner bay. The reclamation activities, mainly including harbor construction and island-land connection, led to a total land area increase of 231.42 km ². (2) The total length of the coastlines was reduced by magnitudes of 161.99 km and 121.36 km for the mainland and islands, respectively. The average annual change intensity of coastlines changed from -0.05% to -1.85% in the last 100 years and the most intensely changes occurred in 1971-1980 for mainland coasts and 2006-2010 for islands. (3) The straightening of coastlines was caused by meandering cutting as a result of the continuous decrease of natural coastlines. The artificial degree of mainland coastlines continued to increase, which was much higher than that of island coastlines. (4) Population growth, economic development and policy guidance were found to be the main driving forces for the coastline evolution in Sanmen Bay.

As a sign element, a large range, long-term shore dynamic changes in the coastal zones, are of great significance to the research of regional coastal environment and human activities. Used the remote sensing techniques, the variation characteristics of Thailand shoreline from 1990 to 2020 was analyzed, such as length changes, type changes, change rate, and the “sea-land” pattern. The results show that: (1) For 30 years, the length of the shoreline of Thailand had a continuous growth trend, but the growth rate was fast at first and then slow down, which patterns were expressed as two kinds: sea-forward expansion and land-forward erosion. From 1990 to 2015, the expansion trend in the shoreline toward the sea gradually slowed, and the erosive trend in the land was gradually increased. The overall change trend from 2000 to 2015 was mainly erosion, but the overall shoreline change in 2015 was expanded to the sea. (2) Thailand shoreline regional variation was significant, the change in the expansion of the banks such as Leam ChaBang was dramatic, and the erosion change in the northern part of Bangkok Bay was obvious. (3) The main driving force for the expansion of Thailand shoreline was the construction of coastal projects, and the main factors of erosion variations were the ocean environment and extreme climate, while policy management acted on the whole process of straighten changes.

Sea Surface Temperature(SST) is one of the important marine environmental dynamics elements in the cognition and study of the physical properties and evolution of the atmosphere and ocean, and is also an indispensable component in the composition of marine forecasting. The study of the distribution and evolution of SST is of great significance to the marine economy, environmental protection and national defense security. In this study, a statistical forecasting method based on the similarity coefficient was proposed, and a statistical forecasting model based on the similarity coefficient was constructed to realize the single-point time series forecasting of SST. In the medium and long-term experiments of SST forecasting in the South China Sea, this method has better results than those from Optimal Climate Normals forecasting and ARIMA forecasting methods, which proves the effectiveness of this method and provides a new idea for the medium and long-term forecasting of SST.

To understand the trends of the dominant species of macrozoobenthos and their niches in the intertidal zone of islands off sourthern Zhejiang, the interannual changes and succession of macrozoobenthic community structure were analyzed based on the data collected from the November of 1990, 2006, 2010 and 2016 in Nanji Islands, Beilong-Beiji Islands and Dongtou Islands. The results showed that there were 15 dominant species of macrozoobenthos and the top four dominant species were Tetraclita japonica, Septifer virgatus, Thais clavigera and Nodilittorina exigua.The T. japonica had been gradually replaced by S. virgatusin the past 30 years. In terms of geography, the most dominant species in Beilong-Beiji Islands and Dongtou Islands was T. japonica, while in the Nanji Islands was S. virgatus. The niche breadth ( B_i) of the dominant species was 0-0.97, and species with B_i greater than 0.70 were T. clavigera, Liolophura japonica, S. virgatus, N. exigua, Capitulum mitella and T. japonica, indicating that these species appeared at many resource sites and had strong adaptability to the environment. Species with B_i less than 0.4 were Trichomya hirsuta, Megabalanus volcano, Septiper excisus, Saccostrea kegaki,Mytilus coruscus and Chthamalus challengeri, indicating these species only appeared at very few resource sites and were weak in resource utilization. The niche overlap value( O_ik) of the dominant species was 0-0.96. The species with B_i greater than 0.70 had higher O_ik, and O_ik were all greater than 0.53. The species with B_i between 0.4-0.7 had O_ik among 0.34-0.66, while the species with B_i less than 0.4 had not necessarily lower O_ik, and their O_ik were among 0 and 0.69, indicating that the species with larger B_i had higher O_ik, but species with small B_i may have high or low O_ik.

The evaluation of mussel loss rate caused by marine disasters is a new scientific proposition produced by the intersection of marine science and fishery science. At the same time, it is also a difficult problem in fishery economics and insurance value accounting. The effect of sea wave disaster on mussel loss rate was studied in this research, adopting the third generation wave model SWAN to calculate the significant wave height. The significant wave height with different return periods around Shengsi sea area was calculated, and the relationship between mussel loss rate and significant wave height in Shengsi sea area was analyzed. The results show that when the effective wave height is up to 3 meters, mussel begin to fall off; when the effective wave height is bigger than 9 meters, the probability of mussel loss rate reaching 100% is high.

The distribution of tropical cyclone (TC) track forecast errors in the northwestern Pacific Ocean were studied based on the Japan Meteorological Agency (JMA) 6-hour TC forecast data from 2005 to 2018. The relationship between track forecast errors and western Pacific subtropical high (WPSH) was also analyzed. The results show that the northeast and southwest displacements are the main track errors in all the 0, 24, 48, 72 h forecasts. The ratios of the northeast and southwest track errors to the total forecast numbers for the 24, 48, 72 h forecasts are 61.62%, 64.02%, 66.94%. There is significant difference in spatial distributions between northeast and southwest track errors. The former mostly occur around 16°N, and the latter around 24°N. Further analyzing the relationship between northeast-southwest biases and WPSH, it is found that 70% of northeast track errors occur to the southwest of the WPSH and about 60% of southwest track errors occur to the northwest of the WPSH. Compared to the WPSH in southwest track errors, the WPSH in northeast track errors has a more extensive area and a more northward ridge. The northeast forecast errors tend to happen in WPSH induced westward migration of TCs, and the southwest forecast errors tend to happen in WPSH induced northward migration of TCs.

Diatom mat deposits have been discovered in the tropical western Pacific successively, and its formation time and mechanism are of great significance for the study of carbon cycle in the tropical western Pacific. In this study, high-resolution XRF element scanning, color scanning and AMS14C dating analysis were performed on sediment of core E20, which contains nearly 2.5 meters of diatom mat deposit in the west Mariana Arc. The results showed that the core E20 could be divided into three sedimentary units, those were clay, siliceous ooze, siliceous clay from bottom to top, and elements Ti, Fe, Cu, Br, etc. showed three-stage change, Ca and Si showed reverse change. Based on 14C-AMS ages, E20 reflected the significant environmental changes in the western Pacific since the last glaciation, the bloom time of diatom mats was from 10.9 ka B.P. to 28.6 ka B.P., and the increase of dust input during the last glaciation should be the main reason for the diatom bloom in the oligotrophic tropical western Pacific. Local low-lying topography was conducive to the preservation of diatom mats.

The bacterial community structure of six surface sediment samples which were collected during the 48th China Scientific Cruise in the west Pacific Ocean was analyzed by highthroughput sequencing method. A total of 253012 sequences are obtained, belonging to 41 phyla, 85 classes, 189 orders, 261 families and 322 genera, respectively. Among them, Proteobacteria is the dominant class, which includes three subclasses: γ, α and δ. Their richness account for 24.76%, 20.21% and 6.48% of the total OTU(operational taxonomic units) in the study area, respectively. In addition, Chloroflexi, Acidobacteria, Gemmatimonadetes, Planctomycetes, Actinobacteria, Bacteroidetes and Nitrospirae are also found popular with abundant bacterial genera and species in each category. There are 23 orders with sequence abundance over 1%. Among them, 6 families or 10 genera are the highest dominant groups. Functional genes related to iron and manganese metabolism account for 10.20%, such as Alteromonas (6.90%), Pseudoalteromonas (1.80%), Shewanella (1.00%) and etc. Other functional gene groups related to nitrogen and sulfur cycling are also found. The result of PICRUSt analysis show wide genetic diversity of bacteria involved in various metabolic processes, such as signal transduction mechanism, protein transport, carbon fixation pathways in prokaryotes, quorum sensing, energy conversion, amino acid and pyrimidine metabolism and etc. Compared with other sites, BC1826 site has lower bacterial diversity, but has higher gene abundance of two-component system. Combined with the frequency of grain size curve of each sedimentary analysis, the result speculate that the difference of microbial community structure between BC1826 site and other sites is related to sedimentary disturbance. Based on the comparison with previous reports, the bacterial community structure in the western Pacific seamount area is different from that in the nodule areas of the eastern Pacific area.

Submarine groundwater discharge is a significant source of the rare earth elements (REEs) in the coastal waters, studies on the geochemistry of REEs in the groundwater are very limited. In this study, the distribution, influencing factors and complex speciation of dissolved REEs in the groundwater of Dagu River Basin in Shandong Province were examined by field investigation and simulation. The conclusions have been obtained as follows: the distribution of REEs in groundwater has a great spatial variation, pH and the reductive dissolution of Fe, Mn oxides/hydroxides may be the important factors affecting the concentration of rare earth elements. The REEs speciation mainly exists as LnCO+3 and Ln(CO3)-2. However light rare earth elements are more likely to form LnSO+4 than middle rare earth elements and heavy rare earth elements in the case of high sulfate. And the patterns of the REEs generally show heavy rare earth elements enrichment in groundwater, the preferential adsorption of LnCO+3 by electronegative particles in the aquifer may be the reason for heavy rare earth elements enrichment. Affected by surrounding refineries, all samples have positive lanthanum anomalies. The proportion of anthropogenic lanthanum in fresh groundwater and recirculated seawater are 34%-75% and 42%-57%, respectively.

Based on the measured Chl-a concentration and sea surface spectrum, the Chinese white dolphin inhabited area of Dajin Island in the Pearl River Estuary was taken as the study area, a Chl-a inversion model suitable for CASI aerial hyperspectral and MODIS satellite remote sensing images was constructed and Chl-a concentration inversion was carried out. The results show that the band ratio model has better performance based on CASI images. The Chl-a concentrations in the study area are 0.1-4.4 μg/L, and the relative average error is 14%. Inversed with MODIS, the Chl-a concentrations in the Pearl Estuary vary from 0 to 8 μg/L with relative average error of 17%. In general, the Chl-a in the sea water around Dajin Island is uniformly low. The Carlson eutrophic index calculated based on the concentration of Chl-a indicates that the sea area around Dajin Island is at the level of oligotrophic and mesotrophic, the complex hydrodynamic and high turbidity may be the main factors inhibiting the growth of phytoplankton in the study area.

Electrochemical methods are the main methods for measuring seawater pH. The self-developed electrochemical pH sensor is based on iridium metal and its oxide electrode, a method for its calibration and data correction in seawater environment was established and applied for in-situ testing in nearshore and oceanic environments. The instrument calibration includes (1)Selecting appropriate calibration buffer reagents according to the calibration requirements of seawater pH analysis; (2)Preparing calibration buffer system by replacing the commonly used 2-aminopyridine (AMP) solution with standard seawater. Data correction mainly includes temperature background correction and error correction. Insitu testing in the sea area and comparison with other similar instruments show that the error caused by the difference of calibration system can be up to 1.00 pH unit, and the data correction can improve the testing accuracy from 0.10 pH unit to 3.00 pH unit. The calibration and data correction method of the instrument can effectively improve the measurement accuracy of this self-developed pH sensor.

The evaluation of marine functional zoning implementation is an important tool to supervise the implementation effect of marine functional zoning and improve the planning management system. However, the lack of effective and stable mechanism for implementation evaluation makes it difficult for marine functional zoning to fully play its guiding role in China. Therefore, based on the concept of consistency and planning blue print, a method is put forward to judge the coordination between the current situation of marine utilization and the marine functional zoning from three aspects: the conformity of marine use, the conformity of environmental quality standards, and the influence of utilization and then constructs coordination index of marine functional zoning, in order to build scientific and operable marine functional zoning implementation evaluation method, and Wenzhou is taken as an empirical case. The results show that the evaluation method based on consistency concept and marine function zoning blue print can effectively measure the implementation effect of marine function zoning. The implementation effect of Wenzhou Marine Function Zoning after revision has been significantly improved, which suggests the revision is conducive to promoting marine function zoning to better meet the social and economic development needs of the planned region. The evaluation method can lay the foundation for the compilation of territorial space planning and provide a reference for the evaluation of territorial space planning.

 In order to study the composition and structure of rocky intertidal benthos community in uninhabited islands in Cangnan, Zhejiang, the intertidal benthos investigation was carried out on 11 uninhabited islands in March 2019. The collected samples were identified, and the abundance, biomass and biodiversity indexes were calculated. A total of 58 intertidal benthos species are identified in 11 uninhabited islands, the average density is 857±205 ind/m2 and the average biomass is 2 847.83±1 032.50 g/m2, the Shannon-Wiener diversity index H, Pielou evenness index J and Margalef richness index D are 1.07-1.61, 0.66-0.83 and 0.54-1.30, respectively. Compared with the mainland coastal intertidal zone, uninhabited islands have more distinct ecosystems with rich and diverse biological resources and important ecological values. It is suggested that uninhabited islands should be protected.

To better understand the effects of seasonal hypoxia on macrobenthic communities in Yangtze Estuary, 4 surveys were carried out during summer from 2016 to 2019. Results showed that the lowest bottom-water dissolved oxygen (DO) was 1.51 mg/L, and the bottom-water hypoxia appeared in the Yangtze Estuary in summer from 2016 to 2019. There were significant differences in the species number, abundance, biomass and community structure of macrobenthos between hypoxic zone and non-hypoxic zone. Polychaetes showed greater tolerance to hypoxia，and were the dominant group in hypoxic zone. Mediomastus sp. and Lumbrinereis sp. were the main dominant species in hypoxic zone. Mollusks, crustaceans, and echinoderms showed the opposite trend to polychaetes, and crustaceans showed poor tolerance to hypoxia. Based on the MDS analysis, the community composition of macrobenthos between hypoxic zone and non-hypoxic zone was significantly different. CCA analysis showed that community structure of macrobenthos was influenced by the bottom-water hypoxia in Yangtze Estuary during summer.

There are abundant mesoscale phenomena in the Bay of Bengal and near the mouth of the bay. In this study, a 2.0 version of the Chelton's data set was used, which can distinguish mesoscale eddies in low-latitude regions, and obtain the genesis distribution of mesoscale eddies by tracing. The northwest sea off Sumatra (the area with 5 °N,94 °E as the core) is an important origin of mesoscale eddies. The eddy tracking of Lagrangian method shows that there were 57 cyclonic and 40 anticyclonic mesoscale eddies in the origin (3°N—6°N, 92°E—95°E) during 19932017. Spectrum analysis indicates that there are two significant periods of 180-day and 360-day in sea surface height anomalies. The dynamic mechanism of mesoscale eddies in this origin is the combined effect of topography and wind field, the Rossby wave propagating westward along 5°N increases instability and triggers the mesoscale eddy generation under the action of the ridge topography. The equatorial wind field is an important source of energy in the origin, and the local wind field can induce the polarity of the mesoscale eddy. This study also reveals the reason why the previous literatures described the northwest sea area off Sumatra as a high eddy kinetic area, but failed to identify many mesoscale eddies.

The mid-ocean ridge is where the plates spread and the new oceanic crust forms. There are often well-developed central eruptive volcanic cones in addition to fissure eruptive lavas parallel to the ridge axis. These volcanic cones are of great significance for understanding the local and regional magmatism and tectonic activities. These volcanic cones can be identified using manual or machine interpretation methods based on seabed multi-beam bathymetric data. In this study the automatic extraction method of volcanic cones near the mid-ocean ridge was tried by means of unsupervised classification using the DEM data from Carlsberg Ridge obtained from the Chinese DY24 Cruise. The slope, surface roughness, positive and negative topography and other derivative parameters were calculated based on the original DEM data. The morphological characteristics and spatial features of volcanic cones were enhanced by feature transformation. The ISO clustering unsupervised classification method was selected to cluster and analyze the images after feature transformation. Then the method of landscape shape index in landscape ecology was introduced to complete the automatic extraction of volcanic cones. The accuracy of automatic recognition can reach around 0.8 with overlapping rate of ~0.7 comparing with manual extraction. Thus, the automatic extraction of submarine volcanic cones by means of unsupervised classification is robust and efficient, which can be of great help to large-scale data process and interpretation.

The passive continental margin ocean-continent transition zone of the southwest subbasin of the South China Sea is located in a strong extension area of the continental margin, which contains rich information about the critical extension and rupture of the lithosphere and the expansion of the ocean basin. In this research, the multi-channel seismic profile and gravity anomaly data were used to classify the passive continental margin structural units of the southwestern subbasin, the structural features of the southern and northern ocean-continent transition zones of the continental margin were studied, and the evolutionary process of continental margin extension was discussed. Multi-channel seismic profile data show that the northern ocean-continent transition zone develops rift-period rifts and tilting fault blocks that tilt toward the sea; in the southern, there are rift-period rifts controlled by low-angle normal faults, submarine volcanoes, and local uplifts. From land to ocean, the gravity anomaly changes significantly. According to above results, the passive continental margin of the southwest subbasin of the South China Sea is divided into three structural units: the proximal zone, the ocean-continent transition zone and the ocean basin, corresponding to the three stages of its extensional evolution process: pre-rift stage, continental margin rift stage and seafloor spreading stage.

Sea surface salinity is an important physical quantity for studying ocean changes and its climate effects. In this study, it was compared the monthly and daily average sea surface salinity products of the SMAP satellite in 2018 with the monthly average grid products and real-time scattered salinity data of Argo respectively, its accuracy was assessed and the global sea surface salinity distribution characteristics were analyzed. The results show that the average monthly product RMSE of SMAP satellite is 0.17, BIAS is 0.11, STD is 0.17, R is 0.98, and the t-test shows a significant correlation; the average daily product RMSE of SMAP satellite is 0.28, BIAS is 0.23, STD is 0.26, and R is 0.81. Compared with the monthly average product, the accuracy of average daily product is lower. The monthly average product deviation of SMAP satellites is small in mid-latitude seas and larger in high-latitude seas; the average daily product deviation of SMAP satellites is -0.6~0.6 in the Pacific Ocean and exceeds 1.0 in the Mediterranean Sea. The global sea surface salinity is between 25.0 and 40.0, among which the Atlantic sea surface salinity is generally higher than those of the Pacific and Indian Oceans, and the global sea surface salinity has an obvious zonal distribution pattern in the latitude direction.

While the reclamation project expands the land space to the coastal areas, it will also have a significant impact on the topographic changes of the project sea area. Based on the measured data and the results of the Delft3D mathematical modeling,  taking the eastern sea area of Ruian, Wenzhou as the research area in this study, the characteristics and dynamic mechanism of the topographic erosion and deposition changes caused by the Oufei Tidal Flat Reclamation Project were analyzed. Studies  show that the topography of the sea area has changed significantly after the implementation of the project, but the distribution characteristics of erosion and siltation in different areas are not consistent, and the dynamic mechanisms that cause changes are also different. From an overall point of view, the dominant feature of rising tides in the research sea area has been enhanced, and the coastal sea area maintains an overall siltation situation, and the siltation rate has increased slightly. From a local point of view, the vicinity of the dike bulge is affected by the effect of flip flow, which shows slow erosion, and at the concave corner of the dike affected by the blocking flow effect, it appears as rapid silting. The above results have important reference value for guiding the protection and utilization of Oufei Tidal Flat and other similar tidal flats.

In order to understand the geochemical characteristics in surface sediments from Sanya offshore area, the contents of 23 trace elements in surface sediments of 331 stations were determined. Multivariate statistical method was used for correlation and R-type factor analysis to explore the source, distribution characteristics and control factors of elements in the study area. The determination of trace elements show that the average values of Sr, Ba, Zr and Rb are higher than those of other elements; The contents of 15 elements such as Be, Cr, Co, Ni, Cu, Zn, Cd, Sb, Pb, U, Zr, Ba, Sc, V and Ga are close to those of stream sediments, surface soil and deep soil in Hainan Island. It is speculated that the sediments mainly come from Hainan Island. The spatial distribution of elements in the study area is complex. In the middle and east, the contents of most trace elements(15) represented by Li increase with the increase of offshore distances; The distribution characteristics of Cd, Sb, Zr, Ba, Rb, Sr, As and Hg are significantly different from other trace elements. The source and distribution of 15 elements such as Li are mainly controlled by the adsorption of terrigenous clay minerals, the source and distribution of Sr are mainly controlled by marine biogenic sedimentation, the source and distribution of Zr are mainly controlled by heavy minerals, the source and distribution of Ba and Rb are mainly controlled by the geological background of the study area, while the source and distribution of Cd and As are related to human activities.

Using the MODIS remote sensing data from Jan. 2003 to Dec. 2019, and combining with the data of sea surface temperature(SST) and wind speed(WS), the chlorophyll concentrations distribution in the mid-western South China Sea and their controlling factors were discussed. The results showed the seasonal variations of the spatio-temporal distribution of chlorophyll concentration in the study area. EOF decomposition indicated that EOF1 probably reflected the impact of extreme weather such as typhoons on the concentration of chlorophyll, while EOF2 and EOF3 reflected influence of the coastal upwelling. The correlation analysis showed that the concentration of chlorophyll had good positive correlation with the WS (r=0.87, p<0.01), and negative correlation with SST (r=-0.59, p<0.05). In summer, the upwelling current formed along the southeastern coast of Vietnam under the influence of southwest monsoon, and it resulted in flourishing of phytoplankton and increase of chlorophyll concentration. In winter, the mixing of upper ocean layer became strong and the nutrient supply increased under the influence of strong northeast monsoon. It promoted the growth of phytoplankton and resulted in higher chlorophyll concentration than that in other seasons.

A large scale mud deposit associated with the Changjiang (Yangtze River) has been formed over the inner shelf waters of the East China Sea. It serves as both source and sink for finegrained sediment and organic matter. Three scientific problems in regional sediment dynamics have been identified, i.e., the processproduct relationships of the mud deposit, the role played by the mud in ecosystem dynamics, and the potential of future magnitude of the carbon reservoir contained in the sedimentary system. The research topics include the future evolution of the Changjiang mud deposit, the generation of sediment gravity flows, organic matter content in the deposit in relation to water column primary production and hypoxia, wave energy attenuation over the mud bed, the decay of particulate organic matter in response to resuspension, and the carbon reservoir pattern in relation to the evolution of the mud deposit. Such research requires an enhanced ability to collect longterm, continuous, highresolution data associated with the benthic boundary layer, the water column and some new sources (e.g., data derived from in situ imagery analysis). The bottom boundary layer data are useful to the studies on sediment gravity flow, wave energy dissipation over the mud area, and the turbulenceinfluenced sediment initiation conditions. The water column data will help to establish the delay curves of organic matter, which is critical to deal with the organic matter burial rate, the formation of shallow gas, and the carbon reservoir issues. Furthermore, there is a demand to collect innovative types of data, to obtain additional information on material source and mud deposit evolution, which awaits technological breakthroughs from the observation systems.

The river-estuary-coastal ocean continuum (referred to as the continuum hereinafter) is a transition zone connecting lands and oceans. The carbon budgets in the continuum are dynamic and uncertain components in global carbon budgets. This complex landocean interactive ecosystem can absorb atmospheric CO2 through photosynthesis and dissolution of CO2. Also, the carbon fixed by photosynthesis or chemical weathering in land and watershed can be transported horizontally to the shelf waters and open oceans. In this paper, the progress of carbon cycles in the continuum is reviewed by taking the famous Chesapeake Bay and Changjiang Estuary-East China Sea continuum as typical examples. It is concluded that systematic observation characterized with land-sea coordination, sea-space integration, point-line combination, should be combined with physicalecological numerical simulation to reveal the multiple time-space scale processes. The strategy is generally operable, and the historical retrospective of results is also achievable. Thus, it can be used to clarify the evolution of carbon exchange along the river-estuary-coastal ocean continuum and their influences on carbon budgets under the combined pressures of climate change and anthropogenic activities.

The combination of human activities and natural factors has formed the eutrophication of the Changjiang (Yangtze River) Estuary and its adjacent waters, leading to increased hypoxic condition in the bottom water in summer, which has become an important signal of the deterioration of ecosystem health. This paper combs the important understandings gained from the recent studies of hypoxia in this area, analyzes multiscale temporal changes of dissolved oxygen, e.g., focusing on the tidalscale, eventscale, and interannual scale, and factors relevant to stratification and material transport. The relevant mechanisms analyzed includes processes such as the diluted water extension, Taiwan Warm Current, fronts, wind field and tides that affect oxygen consumption or transport process. It is also revealed that the main hypoxia phenomena were separated in the Changjiang Estuary and the coastal waters of Zhejiang Province. The similarities and differences in the formation and evolution of the two hypoxic zones were presented. At present, a solid foundation has been laid for the understanding of the hypoxia occurrence, however due to its multiscale temporal variations, field experiments and quantitative studies should be strengthened from a multidisciplinary perspective, and the longterm evolution trend of hypoxia in this area should also be clarified based on longterm time series monitoring.

The acquisition of seawater carbonate system parameters is essential to understand the carbon cycle in coastal ocean, the pattern of CO2 sources and sinks and assess the potential of carbon sinks. Based on the data obtained by 4 seasonal cruises conducted off Changjiang (Yangtze River) Estuary and adjacent East China Sea in March, July, November and December in 2011, we discuss the seasonal and spatial distributions of dissolved inorganic carbon (DIC) and total alkalinity (TA) and their influencing factors. The results showed that the averaged DIC and TA concentrations in inner shelf were increased from summer to autumn, then winter to spring; In cross-section distribution, DIC and TA in summer and autumn showed stratification pattern due to the influence of Changjiang Diluted Water, while in spring and winter, DIC and TA were vertically uniform due to mixing. In inner East China Sea shelf, transect DIC showed a significant negative correlation with temperature and dissolved oxygen, while TA was less regulated by temperature and dissolved oxygen changes, but positively correlated with salinity. DIC was significantly positively correlated with apparent oxygen consumption (AOU), while pH was significantly negatively correlated with AOU. The slope of pH/AOU in the outer East China Sea shelf was -0.002 7 pH/(μmol·kg-1), which was much higher compared with that of -0.001 8 pH/(μmol·kg-1) in the inner shelf. The inner East China Sea shelf seawater (water depth is less than 200 meters) was affected by seasonal ventilation and had stronger carbonate system buffer capacity, which alleviated the seasonal acidification in the subsurface water induced by organic matter decomposition.

Controlling mechanism of air-sea carbon flux in estuary-shelf continuum is important for understanding the role of ocean in “carbon neutrality” goal of China. Based on underway sea surface partial pressure of CO2 (pCO2), temperature and salinity in the Changjiang (Yangtze River) Estuary-East China Sea in spring of 2017, the spatial variations of pCO2 in four domains of the Changjiang Estuary-East China Sea continuum were presented. The roles of water mass sources, organic matter production and decomposition in controlling pCO2 were discussed semi-quantitatively. The results indicated that water mass sources were key factors in determining pCO2 and air-sea carbon flux in the Changjiang Estuary-East China Sea continuum. In addition, production and decomposition of organic matters also influenced pCO2 significantly. Influenced by Changjiang discharge, surface waters in the inner Changjiang Estuary and Zhejiang coast had relatively high pCO2, served as source of CO2 to atmosphere, with magnitude of 5.36 mmol·m-2·d-1. The north and east of study area were influenced by the Changjiang Diluted Water, and Kuroshio Surface Water, respectively. While, they were both carbon sinks with magnitude of -15.44 mmol·m-2·d-1 in the north study area. The average air-sea carbon flux in study area in spring of 2017 was -6.73 mmol·m-2·d-1. End-member mixing model revealed that decomposition of organic matter increased pCO2 of the inner estuary by about 200 μatm, which transferred the inner estuary from carbon sink to carbon source in spring; the shelf waters were carbon sink if water mass sources were considered only, while biological production decreased pCO2(decreased 144 μatm) further, and enhanced the carbon sink.

Base on underway surface CO2 data obtained from Changjiang (Yangtze River) Estuary and adjacent area in August 2019, combined with the temperature, salinity, dissolved oxygen and other parameters, the spatial variation of pCO2 and its controls during late summer were discussed briefly. The results show that the pCO2 generally decreases with distance offshore, and is the lowest in the mesohaline zone of river plume. After removing temperature effect, the good negative correlation between temperaturenormalized pCO2 and DO% indicates that biological processes are the main reason for the spatial variation, and the strong sink for atmospheric CO2 just results from high biological production. Moreover, the section distributions of temperature, salinity and DO% in the riverocean mixing zone show that the influence from vertical mixing on pCO2 is minor due to the water stratification. On the whole, the airsea CO2 fluxes for the study area are -2.0±5.2 mmol·m-2·d-1, showing a carbon sink with respect to atmospheric CO2. However, with environment changes and human perturbation such as the decrease of Changjiang runoff, Changjiang Estuary and its adjacent area may gradually shift from a sink to a source, which is necessary for us to pay more attention and further study.

Abstract: The impact of the flood event on the distribution and source of particulate organic carbon(POC) in Changjiang (Yangtze River) Estuary and adjacent waters was analyzed based on the data of temperature, salinity, total suspended matter(TSM), POC and δ13CPOC ,which were collected during the July 2020 flood. The results show that POC is negatively correlated with salinity (r2=0.41, p＜0.01), and positively correlated with TSM (r2 =0.92, p＜0.01). The mixing of salt and fresh water is an important factor affecting the distribution of POC. The distribution of δ13CPOC values in the surface water indicates that the phytoplankton production is another important factor affecting the distribution of POC in the northeastern part of the study area. Flood events reduce the concentration of terrigenous POC due to the dilution of high runoff, meanwhile, light δ13CPOC values in the southeastern part of the study area indicate that flood events could expand the influence range of terrigenous POC in the East China Sea.

The Changjiang (Yangtze River) Estuary has been subject to the double pressure of human activities and natural changes for a long time. As a result, the change of environmental factors may lead to a great alteration of phytoplankton community composition in this area. To explore the composition and variation of phytoplankton community in the Changjiang Estuary and compared with historical data, phytoplankton samples were collected vertically using net trawl method during “LORCE” cruise in August of 2017. Among all the samples collected, 7 phyla, 86 genera, and 205 species were identified, their total abundance was 1.47×105 cells/L. The results showed that diatoms and dinoflagellates accounted for 95.8% and 1.2% of the total phytoplankton abundance, respectively. Warmwater species, including Pseudonitzschia delicatissima (56.35×103 cells/L), Trichodesmium thiebautii (3.30×103 cells/L), Pseudosolenia calcaravis (3.05×103 cells/L), Chaetoceros lorenzianus (2.64×103 cells/L), Proboscia alata (1.89×103 cells/L) and Coscinodiscus gigas (1.71×103 cells/L), were dominant in the phytoplankton community. Their total abundance was 68.94×103 cells/L, which accounted for 47.00% of the total abundance of netcollected phytoplankton. High abundances of these warmwater species were observed near the front formed by the convergence of the Changjiang Diluted Water and Taiwan Warm Current. Spearman’s rank correlation showed that C. lorenzianus and P. calcaravis were negatively correlated with phosphorus, C. gigas were positively correlated with the concentrations of dissolved inorganic nitrogen, and P. calcaravis was positively correlated with salinity, C. lorenzianus and C. gigas were negatively correlated with salinity. Compared with the summer dominant phytoplankton species during the past 30 years, it was found that warmwater species of phytoplankton in the Changjiang Estuary increased significantly and their distribution area expanded northward. It was speculated that this phenomenon was highly associated with sea temperature elevation and the enhancement of warm current.

 In summer, large areas of low dissolved oxygen or hypoxia are prone to occur in the bottom waters of Changjiang (Yangtze River) Estuary. The zooplankton community (＞160 μm) in hypoxic area (DO＜2 mg/L), low dissolved oxygen area (2 mg/L＜DO＜3 mg/L) and normal area (DO＞3 mg/L) of the Changjiang Estuary in summer of 2016 and 2017 were compared. The results showed that the abundance and biomass of zooplankton in hypoxic area were significantly higher than those in the low dissolved oxygen area and normal area in 2016. The abundance of small mediumsized copepods and gelatinous zooplankton in hypoxic area and the low dissolved oxygen area were all higher than those in the normal area. It was dominated by filterfeeding of the class Thaliacea and Appendiculata in the summer of 2016 when the degree of hypxia was more serious, but in the summer of 2017, it was dominated by carnivorous Chaetognaths of the class Sagitta.

As the pilot of constructing HighFrequency(HF) ground wave radar observation network in LORCE plan, a pair of OSMARS50 HF ground wave radar was set up in Guojushan and Baimajiao of Liuheng Island, facing the Niubishan Channel of Xiangshangang Bay. To verify the accuracy of the synthesis surface current from HF ground wave radars, 25 hcontinuous observations were carried out using the Valeport Propeller Current Profiler and ADCP in the core of the effective area of this pair of HF ground wave radar. Comparison of currents shows a good correlation between data from the fixedpoint current and the HF ground wave radars, which suggests that currents obtained by the HF surfacewave radars at this point have a relatively high accuracy. At the same time, the availability of the HF ground wave radar data in large region is also tested by simulated results using a regional model established by SCHISM. Results show that the observation and simulation are consistent in the general trend: the Niubishan Channel is a regular semidiurnal tidal area, and M2 is the main tidal component, while the semidiurnal tidal component M2 and full diurnal tidal component K1 are mainly reciprocating currents. During flood tide, the sea water flows to the interior of Xiangshangang Bay first through the Niubishan Channel, and then to the Fodu Channel after a period of time. During ebb tide, the sea water in Xiangshangan Bay first flows out to the sea through the Niubishan Channel, and then the sea water from Fodu Channel gradually flows into the Niubishan Channel.

 The temporal and spatial change characters of coastline and tidal flat in the islands with different principle functions in the Zhoushan Archipelago were analyzed, using a coastal remote sensing monitoring dataset with 30 m spatial resolutions at annual interval from 1986 to 2017. The results suggested that the coastlines in Zhoushan Archipelago advanced toward the sea, with many water areas(152 km2) and tidal flats(18 km2) reclaimed into lands and the government policies were the main driven factors. The change characters were various among the islands with different principle functions. In particular, the land reclamation was significant in the islands with the principle functions of comprehensive development, coastal industry, coastal tourism, and harbor and logistics, accounting for 96% of the archipelagos new lands. The land reclamation was slight in the islands with marine science and education and scientific fishery functions, accounting for 4% of the archipelagos total new lands. Meanwhile, the coast was stable and well protected in the islands with ecological conversation and clean energy functions. The results could provide scientific basis for coastal zones ecological protection and restoration projects, as well as the marine principle functional zoning.