A high resolution numerical model based on a proven FVCOM with a Lagrangian particle tracking module was introduced to simulate water particle movement under differences controlling conditions, including the tide, wind, boundary circulation flow, temperature, salinity, wave coupling etc. Combined with simulate results and the actual drift bottles movement paths, factors influencing Ulva prolifera were discussed. The results showed that the migration path of U. prolifera firstly migrated northward along the coast of northern Jiangsu to the sea area near the abandoned Huanghe River Estuary and then continued its migration to the sea area south of Shandong Peninsula. The external forces that affecting the migration of U. prolifera is mainly wind. It is an order of magnitude higher than anything else and followed by temperature-salinity, wave, tidal, circulation, the tidal current can cause the cyclic movement of U. prolifera in the local area, and it has no influence on Enteromorpha for drifting to the north more distant. During the simulation period, the surface temperature, salinity of drifting sea area were between 18−24℃, 28−31, respectively. These temperature and salinity conditions are close to the most suitable growth conditions of U. prolifera, indicating that U. prolifera would fast reproduce during its drifting.

Transparent exopolymer particles (TEP) play an important role in the marine micro-food web and the marine carbon cycle. The distribution patterns and influencing factors of TEP in the coast of eastern Fujian in summer are investigated in this research. The results show that the contents of TEP (calculated with xanthan gum as the standard substance, the same below) in the coast of eastern Fujian ranged from 25.2 μg/L to 935.5 μg/L, with an average value of (201.8±177.9) μg/L. The level of TEP is high in the near-shore and low in the far-shore, which in surface layer is lower than that in bottom layer. Correlation analysis shows that TEP in the research area are positively correlated with turbidity, silicate, phosphate, nitrite, nitrate and ammonium concentration, negatively correlated with pH, DO concentration and Net-level phytoplankton. The results of chlorophyll a fractions show that Net-level phytoplankton in the area may contribute more to TEP than other size phytoplankton. Comparing with phytoplankton as the main controlling factor of TEP in the open ocean, TEP in the coast of eastern Fujian in summer are mainly produced by phytoplankton in the decline stage, and its distribution is mainly affected by the resuspension of particles. The results can not only further clarify the differences between the influencing factors of TEP in the coastal waters and the open ocean, but also supplement the gaps in the study of TEP distribution in different regions of coastal waters in China.

To investigate the changes in mercury (Hg) speciation in vegetated sediments of the wetlands in Changjiang River Estuary, China, following the invasion of Spartina alterniflora, we determined total mercury (THg), methylmercury (MeHg), toatal organic carbon (TOC), reduced sulfur (S) and grain size in core sediments (0−40 cm) vegetated with different plants in wetlands. The results showed that: (1) the mean concentrations of THg were 49.9−100.9 μg/kg in sediments vegetated by S. alterniflora, Phragmites communis, Scirpus mariqueter and Scirpus tabernaemontani had a significant positive correlation with the fraction of fine particles (<16 µm) and TOC content (r²=0.85, p<0.01; r² =0.58, p<0.01), indicating that the distribution of Hg levels in sediments could be dominated by the spatial differentiation of the mineral-organic complexes in fine particles. The invasion of S. alterniflora promoted the deposition of fine particles, and thus could facilitate Hg storage indirectly in wetland sediments. (2) The mean concentrations MeHg and average values of MeHg/THg (%) in vegetated sediments were 0.3−1.4 μg/kg and 0.4%−1.4%, respectively. The profiles of MeHg and MeHg/THg exhibited decrease with increasing depth across all sites. There was no significant difference in the content of MeHg and the values of MeHg/THg in vegetated sediments dominated by S. alterniflora, P. australis and S. mariqueter, indicating that the impact of S. alterniflora invasion on Hg methylation may be limited. In addition, there was no significant positive correlation between MeHg/THg and THg, TOC and acid volatile sulfur (AVS). S-K edge XANES further revealed that the reduced sulfur (S) (e. g., thoil and sulfide) changed greatly in depth profiles. These results suggested that the changes in reduced sulfur could have limited impacts on MeHg production. The values of MeHg/THg was higher in surface horizon (0～8 cm) than in deeper horizon, indicating that the higher rates of Hg methylation in surface sediments and the degradation of fresh organic matter (e. g., algae and plant litter) could be the key biogeochemical process on controlling MeHg production in surface sediments of wetland in Changjiang River Estuary.

The Zhujiang River Mouth Basin is a petroleum-bearing basin with a high degree of exploration in the northern continental margin of the South China Sea, the analysis of fault characteristics is crucial to its basin evolution model and hydrocarbon accumulation mechanism. According to the high-resolution seismic data and drilling data, the fine seismic geological interpretation of the Kaiping Sag in the southwest of the basin is carried out. Based on the fault grade and scale, the fault structure type is divided into the first-level basin-controlled fault, the second-level sag-controlled fault and the third-level control fault based on the level and scale of faults belt fracture and four-level control ring fracture, identify “Y” shaped faults, stepped faults, and heart-shaped faults combination styles on the seismic section, identify three plane combinations of parallel, goose, and oblique based on the fault plane distribution Types of quantitative statistics of the fault strike characteristics show that under the action of the right-handed stress field, from the Eocene to the Early Miocene, the strike direction continued to rotate clockwise in the direction of NE→EW→NW, and the fracture activity gradually weakened. It is also believed that due to the impact of the Indian-Eurasian plate collision, the subduction and retreat of the Pacific plate and the continuous southward movement of the ancient South China Sea, the Zhujiang River Mouth Basin formes a typical extensional tensile stress field environment. It contributes to the development of three groups of faults in the near NE direction, the EW direction and the near-NW direction during the Eocene-Oligocene period. It provides an explanation and supplement to the geological structural characteristics of Kaiping Sag, and provides a reference for the development characteristics and genetic mechanism of the ocean-continent transition zone on the northern margin of the South China Sea.

Based on the analysis of the rare earth element (REE) geochemical characteristics and clay mineral assemblages of Core TS6 sediment samples in the southern area of Southwest Taiwan Basin, South China Sea, the provenance and characteristics of its changes, material transport mechanism of sediments in the study area over the last 19 ka (the last deglaciation) are discussed. The comprehensive analysis of provenance shows that the rivers in Taiwan are the main provenance of sediments in the study area. The rivers in the west of Taiwan contribute more than the rivers in the east, and the Zhujiang River also transports part of sediments to the study area. Due to the large differences on the types and contents of the main clay minerals in different provenance areas, it is judged that the illite and chlorite of the clay minerals in the study area are mainly provided by the rivers in Taiwan; the kaolinite is mainly provided by the Zhujiang River and the less content of montmorillonite is provided by Luzon Island in the southeast. Since the last deglacial period, the input of terrigenous materials in the study area has been gradually reduced under the control of sea level changes. The provenance changes reflected by the combination of clay minerals are mainly controlled by changes in climate and ocean currents, and the influence of multiple factors may be superimposed.

The radial sand ridges is a typical sedimentary accumulation body distributed off the coast of Jiangsu Province. Under the influence of the sediment supply of the Changjiang River and the Huanghe River as well as the coastal tidal current, the typical silty-muddy tidal flats are developed, and the sediment elements can record the important information of the environmental changes of the tidal flats. Three short core samples were collected in the tidal flat of radial sand ridges to establish a reliable chronological framework and geochemical element testing, and 14 elements with high X-ray fluorescence (XRF) core scanner analysis signal strength were selected for clustering and correlation method to extract environmental information. The sedimentary environment changes of the northern Jiangsu radial sand ridges under the influence of human activities and coastal environment changes in the past 100 years were studied. The results indicate that the contents of Si, Ca and Fe in the core sediments of typical tidal flat profile in this area are relatively high, and the contents of Si, Ca and Fe increasing from north to south, while the contents of Mn, Ba, Cu and Zn are low, and the little changes in contents at all profiles changes. In terms of vertical change, Si, Ca and Fe have the same vertical change trend, while Ni, Zn and S have the opposite change trend with Si, Ca and Fe in different sediment cores. Correlation and clustering analysis show that Si, Ca and Fe have high correlation, that is, they have similar geochemical behavior and consistent material source. In addition, it is negatively correlated with elements Ni, Cu and Zn, suggesting that these elements have different geochemical behaviors with the former. The sedimentary environment changes of the tidal flat are obvious and show different patterns in different regions in the northern Jiangsu radial sand ridges, and the material source, hydrodynamic environment and human activities are the main reasons leading to the change of the sedimentary environment.

The submarine topographic features and distribution types of the Xuande atoll in the Xisha Islands have important indications for the influence of regional geological structure, sea level rise and fall, and ocean hydrodynamics. In order to study the submarine topography and geomorphology of the Xuande atoll, we detailed survey in the Xuande atoll of the Xisha Islands, including side scan sonar, single-beam sounding, and surface sediment sampling. The results show that: (1) Xuande atoll is a type of incomplete atoll, with lagoon deposits in the middle, and four water channels with a water depth of about 60 m had been divided, namely, the gate of the Xishazhou at the northwest of the atoll, the “Red Grass Gate” of the Nanshazhou-Yongxing, the gap on the west side of the atoll, and the gap on the south side of the atoll; (2) according to the geomorphic features, the underwater geomorphic types of the Xuande atoll are divided into 3 grades and 11 types of grades classification systems. The dynamic geomorphology units such as sand waves and grooves in the study area show that the submarine features in the shallow water area of Xuande atoll are controlled by prevailing monsoons and wave sites. The tidal channel water body formed by the deep water entrance is the main factor shaping the dynamic geomorphology of the Xuande atoll lagoon area. There are six levels of underwater terraces on the seaward slope in the southeastern part of the study area. By comparing the characteristics of the coral reef terraces in the South China Sea, the genesis of the seaward slope terraces on the Xuande atoll is likely to be a combination of global sea level changes and crustal subsidence.

DNA barcoding technology is a tool for rapid and accurate species identification using short orthologous DNA sequence. In this study, both traditional morphology and DNA barcoding technology was used to accurately identify ichthyoplankton species in the Changjiang River Estuary and its adjacent waters. Morphological description was carried out at the same time. The results showed that in spring and summer of 2016 and summer of 2017, 55 species of ichthyoplankton were obtained, belonging to 9 orders and 19 families. Among them, there were 35 species of Perciformes at most. The seasonal variation of ichthyoplankton in fish group was not obvious, while there was significant seasonal variation in species. Only Coilia mystus, Engraulis japonius and Larimichthys polyactis appeared both in spring and summer. It was the first time to describe the morphological characteristics of Harpadon nehereus larva and juvenile. In addition, the quantifiable characters, fin development and melanin distribution of larvae and juvenile of Harpadon nehereus, Chelon affinis, Eleutheronema tetradactylum, Sillago japonica and Paraplagusia japonica, were described and drew. The research could provide a scientific basis for the study of fish nursery in estuaries, and also provide a new way for the accumulation of taxonomic data in the early stage of fish development.