The ECCO v4 outputs from 1992 to 2015 is used to diagnose the heat content change in the equatorial Pacific box (118°E-75°W, 5°S-5°N, 0-300 m) and the Niño 3.4 box (170°-120°W, 5°S-5°N, 0-80 m). In the interannual time scale after removing the seasonal cycle, the temperature tendency term is driven by meridional heat transport and balanced by the surface heat flux term in the equatorial Pacific box. The transport across 5°N plays a dominant role in determining the magnitude and sign of temperature tendency term. For the Niño 3.4 box, the temperature tendency term of heat content is driven by the heat transport term and balanced by the surface heat flux term, with vertical transport playing an important role. The meridional heat transport of the equatorial Pacific box leads the vertical heat transport of the Niño 3.4 box on the interannual time scale, which explains why the heat content change of the equatorial Pacific leads the Niño 3.4 SST change by several months during the ENSO (El Nino-Southern Oscillation). Though there are subtle differences between the eastern Pacific and central Pacific ENSO events, two types of ENSO bear similarities in terms of heat content change mechanism. For the equatorial Pacific box, meridional heat transport plays a major role in determining its heat content change. For the Niño 3.4 box, vertical transport is the dominant term driving the heat content change in both developing and decaying stages of ENSO events.

Diffusive convection driven by temperature and salinity is a ubiquitous phenomenon in the mid and high latitudes of the ocean. Numerical simulation of diffusive convection can be used to study small-scale dynamic processes of the ocean. In this study, we analyze the formation mechanism of diffusive convection and establish a two-dimensional cavity model. The governing equation of the model is solved by the finite volume method, and the process of layering phenomenon is simulated numerically. The temporal evolution of temperature and salinity of the flow field is given, and the vortex structure of the velocity field is simulated. The processes of the formation and merging of diffusive convection staircases are analyzed, and a theoretical explanation for mass and energy transport processes is given. In addition, the diffusive convection under different heat flux density is discussed. It is found that the growth rate of diffusive convection staircases increases with the increase of heat flux density, and the cooling from the upper boundary plays an important role in accelerating its growth. The variation of heat flux density does not have a significant impact on the evolution of diffusive convection staircases.

The wind on the water surface can create wind waves. The exchange mechanism of momentum and energy due to the turbulence of wave current is a complicated process. Wind stress is generally used to describe this energy exchange, and can be divided into three components: shear stress, wave induced stress and turbulent stress. An effective nonlinear wave current separation method, namely, the Nonlinear Stream Function Method (NSFM), is used to qualitatively describe the momentum and energy transports between wave and current. An analytical stream function is constructed, which can effectively express nonlinear waves and satisfies the Laplace equation, the boundary condition and the kinematic boundary condition of the water surface, separating the wave-induced velocity field based on the laboratory wind-wave data. Through the cross-spectral technique, the contribution of wave-induced Reynolds stress to wind stress at different wind speed is obtained. The results are as follows. NSFM has higher accuracy and better applicability in treating wind waves under different working conditions. With the increase of wind speed, wave-induced stress decays faster along water depth, and the ratio of wave-induced stress at the free surface to the momentum transport mechanism should be gradually weakened.

The surface level variation greatly depends on semidiurnal and diurnal tidal species in the estuaries of irregularly semidiurnal tides. However, fortnightly tidal species have a great impact on the mean water surface topography upriver due to substantial difference in damping of the main different tidal species. Therefore, the effect of different tidal species on tidal level distribution has obviously regional characteristics when tides propagate into deltaic river networks. In this paper, a one-dimensional flow model of the Pearl River networks was used to obtain a series of high-frequency and long-period tidal levels. Then, spatial distributions of the four main tidal species in the study area were obtained for further study by continuous wavelet transformation (CWT) and reconstruction. Finally, a new pixel affinity for spectral image segmentation was employed to compare the similarity between two figures, which implied a spatial correlation of tidal species and tidal level distribution in the complex river network. The results showed that surface level variation is influenced by semi-diurnal and diurnal tidal species near the outlets, while mean water surface topography is influenced by fortnightly tidal species in the complex river network.

Based on the analysis of data obtained from the China Meteorological Administration (CMA) (1949-2016) and State Oceanic Administration (SOA) (1989-2016), the trend of tropical cyclone and storm surge disaster along the northern South China Sea was examined in this study. The result indicated that the annual frequency of typhoons had been decreasing slightly but the influence of powerful typhoons and typhoon intensity showed a rising tendency. The frequency of landfall typhoons had experienced significant transformation in the mid-90s. Eastern Guangdong was frequently affected by high-intensity typhoons, and typhoon intensity in western Guangdong had increased year by year since 2007. Typhoon intensity gave the accordant distribution in the four study areas. Four typical paths of storm surge were summarized, and variations of intensity and regional distributions of typhoons with different incidence angle ranges were also analyzed in the study. We found that both the frequency of strong storm surge disaster and the level of annual maximum storm surge had increasing trends along South China coast in recent years.

Algal turf scrubber (ATS) is a system for water cleaning, which uses intertidal algae to effectively eliminate nitrogen (N) and phosphorus (P) elements in eutrophic water. Algae is the most important organism in the whole system, and its community structure is closely related to the effect of water purification. Based on the high-throughput sequencing technology of Illumina MiSeq platform, we analyze the diversity of algal samples in ATS system and natural reefs in this study. The results of 18S rDNA show that the ATS system obtains 21390 algal majorizing sequences. Among these majorizing sequences, Antithamnion accounts for 22.79% of the total number, and the rest sequences are classified as Psammodictyon, accounting for 19.07%. Algae in Song Jing, Zhan Nanting and Hou Zhai areas have 88435, 87129 and 106458 majorizing sequences after filtering, respectively. They are mainly Chroodactylon, Mastocarpus and Mazzaella. Both the ATS system and the natural environment samples have the dominant species of Skeletonema and Ceramium. This research shows that the ATS system has similarity and specificity in its community structure compared to the natural reefs, which provides a theoretical evidence for further improving the function of the ATS system.

Although seagrass meadows play a key role in ecosystem services by providing high productivity, their distribution areas have been declining sharply, resulting from global climate change and increased human pressures. Therefore, it is urgent to strengthen the protection and restoration for seagrasses. In this study, we tried to use seed planting method to recover the Enhalus acoroides meadow in Li’an Lagoon. Results showed that the burial depth and mesh bag protection profoundly affected the seed germination. When the burial depth was 6 cm, seed germination was very low, at 1.25%. Seeds buried in 2-cm depth with mesh bag protection showed a much higher seedling establishment (96.10%) than the seeds without protection (5.88%) in the first month, indicating that seed loss negatively affected the seed germination rate. The survival of seedlings decreased to 24.4% after three months, probably due to macroalgal blooms in the early spring.

To better understand the polymorphism characteristics of ribosomal RNA genes of Crossorhombus kobensis (Jordan & Starks, 1906) from Bothidae, Pleuronectiformes, a total of 128 clone sequences were obtained, including full-length sequences of 18S, ITS1, 5.8S, and ITS2 and partial fragments of 28S. After sequence alignments, clustering analyses and recombination detection, the results showed that only 5.8S (158 bp) had no length variation, while the other four gene fragments showed high length polymorphism and resulted in several distinct types: 18S (1856-1893 bp) with four types of Types A, B, C, and R; 28S (967-974) and ITS1 (407-505 bp) both had three types of Types A, B and R; ITS2 (423-447 bp) had two types of Types A and B. All five gene fragments showed GC-bias, and ITS2 (71.14%) > ITS1 (65.37%) > 28S (62.22%) > 5.8S (57.67%) > 18S (54.95%). The current characteristics criteria were not sufficient to provide strong evidence for the inference of functional gene or pseudogene of 18S, 28S and ITS sequences. Therefore, comparison with each of corresponding gene fragment of four affinis species from family Bothidae was conducted, Arnoglossus macrolophus, Crossorhombus azureus, Engyprosopon grandisquama, and Lophonectes gallus. The alignment showed that the indels and differential sites of Type A sequences of both 18S and 28S were the similar as those of the four species; and Type A of ITS1, as well as the four species, had no fragment deletion at the missing loci of Type B. Therefore, Type A sequences of 18S, 28S and ITS1 were speculated as functional genes, while the other types were putative pseudogenes. As for ITS2, the divergence loci of Type A and Type B compared to each of the four species had no consistency, and there was no evidence to infer the status of ITS2. In this study, 5.8S rDNA is the most conserved gene, suggesting a concerted evolution, while non-concerted evolution was confirmed in other four genes because of high intra-individual polymorphism.

Toll-like receptors (TLRs) are the major pattern recognition receptors (PRR) of the innate immune system in vertebrates, which can initiate host immune responses by recognizing potential pathogens. The present study focused on the role of Tlr21 involved in immune responses in lined seahorse (Hippocampus erectus). The full-length sequence of the lined seahorse tlr21 gene was cloned. The open reading frame (ORF) of seahorse tlr21 gene includes 2964 base pairs, which is predicted to encode 981 amino acids. The encoding protein had a predicted molecular mass of 246.98 kDa and an estimated isoelectric point of 4.78. Homology comparison and phylogenetic analysis showed that lined seahorse tlr21 shared high sequence identity with its homologs from other species, especially those species in Syngnathidae. Quantitative real-time PCR analysis showed that tlr21 mRNA was widely expressed in various tissues and expressed highest in the kidney. We conducted intraperitoneal CpG-ODNs injections to the lined seahorses. Both CpG-2007 and CpG-HC4040 increased expression levels of tlr21 mRNA in seahorse kidney significantly. In conclusion, these findings indicated that tlr21 initiated the innate immunity in lined seahorse by recognizing CpG DNA.

The central western South China Sea is one of the main fishing grounds for fishery development. To understand the trophic relationships of major fishery organisms of the central western South China Sea, stable isotope techniques were used to analyze and determine carbon and nitrogen stable isotope ratios of major fishery biological samples in the area. The trophic levels of the main fishery biota were calculated to construct a continuous trophic spectrum of the main fishery organisms in the area. These results show that the major fishery isotope ratios have a wide range of changes in the central western South China Sea. The δ¹³C and δ¹⁵N values of the fish ranged from -20.00‰ to -16.51‰ and from 7.94‰ to 11.81‰, respectively. The δ¹³C and δ¹⁵N values of the cephalopods ranged from -18.84‰ to -17.60‰ and from 10.10‰ to 12.85‰, respectively. The corresponding trophic levels of each species were calculated using zooplankton as the baseline organism. The trophic level of fish ranged from 2.41 to 3.53, and that of cephalopods ranged from 3.03 to 3.84. Among the organisms, the average trophic level of cephalopods is higher than that of fish. Comparison of trophic levels in different lengths (mantle length) of Symplectoteuthis oualaniensis, Thysanoteuthis rhombus, Decapterus russelli, Decapterus lajang, and Thunnus albacares reveals that the trophic level has a correspondingly increasing trend as body length increases. In this study, we preliminarily established the continuous trophic levels’ spectrum of major fishery bio-nutritional levels in the central and western waters of the central western South China Sea, providing a theoretical basis for the food web structure and fishery resource utilization in the area.

Single-grained detrital minerals have been powerful tool for evaluating marine sedimentary provenance due to their advance for weakening the influence of rock types and alteration in the source, transportation and sedimentation on extracting provenance information. In recent years, zircon, garnet, feldspar, pyroxene, amphibole, monazite, and magnetite were used for sedimentary provenance discrimination in marine science. Single-grained mineral major elements and chronology were often utilized to accurately identify geological characteristics and location of source area; nonetheless, trace elements, isotopes and micro-textures were not sufficient So far, the evaluation of marine sedimentary provenance was fragmentary, which could be evaded by multi-mineral techniques. Further, in-depth studies should be conducted to trace the temporal-spatial evolution of source location through zircon monazite, mica and apatite geochronometry, to quantify erosion rates of source rocks and material flux from source and sink through a multi-mineral quantitative model. In this review, single-grained techniques of minerals in marine provenance research were summarized, and prospects are highlighted to carry out better studies on provenance discrimination of marine sediments.

Observations and research on beach responses to storms help deepen our understanding of beach processes. Typhoon Khanun (No. 1720) made landfall in Xuwen, Guangdong on October 16, 2017. The typhoon caused significant impacts on the beaches along the southern Leizhou Peninsula. Based on the field profile survey and sediment sampling before and after the typhoon landfall, beach response characteristics are investigated in this study. The main results show the following. (1) Under extreme wave conditions, the surface sediment became coarser and the sorting was worse. Beach states transformed toward more dispersed states to buffer and adapt to the high intensity wave energy. (2) Beaches and different segments in the same beach had different responses. These differences were influenced by the headlands, bays’ orientations and sizes. Submarine bar or beach berm may occur on the beach profile. Attention should be paid to the roles of geological and geomorphologic factors when studying beach responses to storms. (3) Changes of the Dengloujiao Beach were influenced by the reef flat and the huge sandy headland. The beach response of beach-coral reef flat system to storm needs further study. More detailed observations and studies of beach responses to storms are needed in the future.

A storm surge and wave coupled inundation simulation model for Lei Zhou coastal areas at high resolution has been established based on ADCIRC (a parallel advanced circulation model for oceanic, coastal and estuarine waters) and SWAN (simulating waves nearshore) ocean numerical models. A total of 1415 typhoon cases that seriously impacted Lei Zhou were simulated. The result of contrastive analysis shows that wave has a significant impact on storm surge in Lei Zhou coastal areas. We designed 35 typhoon cases based on 8007 typhoons, and reserve flooded area and submerged depth for seven different grades. The inundated area of Lei Zhou can reach 463.2 km² under 900 hPa grade. We developed 60 cases of possible maximum storm surge and calculated the biggest inundated extent and depth. Under the impact of maximum typhoon, the sea water will spill over seawalls and cause serious flooding disaster. The total submerged area is 602.0 km² in Lei Zhou. The area whose dangerousness is first grade with flooding depth bigger than 3 m is 465.8 km². The eastern coastal areas of Lei Zhou will face larger storm surge disaster risk than the western coastal areas. The results of the study have important implications for guiding prevention and mitigation work of storm surge disaster in Lei Zhou.

A series of laboratory experiments were carried out in a wave flume to study the influences of different reef-flat widths on wave transformation over reef coasts as well as wave-induced setup on reef flats. A series of incident irregular wave conditions were tested based on the idealized reef model with three reef-flat widths. Results show that as waves propagate across the reef, the swell height decays all the way, whereas the infragravity wave height increases gradually along the reef and reaches the maximum at the shoreline. Near the shoreline, the swell height decreases with increasing reef-flat width, but the variation of infragravity wave height with the reef-flat width is not obvious. The effect of varying reef-flat width on wave-induced setup over the reef flat is insignificant. The first resonant mode is identified on reef flat for the infragravity waves, and the level of resonant amplification near the shoreline is determined by the combined effect of reef-flat water depth, incident peak wave period and reef-flat width.

Based on the WRF (Weather Research and Forecast) model and WRF-3DVAR (3- Dimensional Variational) assimilation system, we conduct a single time analysis to initialize Typhoon Chanthu and compare the effects of assimilation radar radial velocity (V_r) on Typhoon Chanthu analysis and forecast, with two radar radial wind data. We show that the role of assimilating radar radial wind is mainly reflected in the adjustment of typhoon intensity and circulation structure; and after the assimilation reaches a certain length of time, it has a positive effect on the improvement of forecast. The assimilation test improves the typhoon's initial wind field and the thermal and dynamic structures, intensity, and location of the typhoon circulation center, thereby improving the typhoon structure, path, and intensity predicted for future 18 hours.

In this paper, the sea surface salinity anomaly (SSSA) index from the EN4 reanalysis data during 1980-2016 is used to distinguish two types of El Ni?o. We identify the salinity variation region which has a close contact with two types of El Ni?o in the tropical Pacific. We demonstrate that salinity time series in different boxes are related sea surface temperature variation, and can indicate two types of El Ni?o. Depending on the key salinity field contrast of their correlation coefficient of temporal and horizontal distribution. Evidently, the region of SSS field is mainly located in the equatorial region with symmetric distribution in the western tropical Pacific during the eastern Pacific (EP) El Ni?o. One significant region of SSS field is migrated westward, another skewing southward east of the dateline as asymmetric distribution during the central Pacific El Ni?o, which is different from the EP El Ni?o. Based on these characteristics, we find key areas of an index that represents two types of El Ni?o and distinguishes them. Finally, we use this index to reproduce recent El Ni?o events.

We aim to study the secondary metabolites from the South China Sea soft coral-derived fungus Eupenicillium sp. DX-SER3 (KC871024). The rice fermentation products of the strain were purified by comprehensive chromatography methods of silica gel column, medium pressure preparative liquid chromatography (MPLC), ostade-cylsilane (ODS), and semi- preparative HPLC. The compounds’ structures were identified by nuclear magnetic resonance spectroscopy, mass spectroscopy, and comparison with the reported data. Five known compounds were obtained and identified as helvolic acid, β-adenosine, 2'-deoxythymidine, N-acyltryptamine, and p-hydroxybenzaldehyde. The high yield of the helvolic acid indicates that this strain has the potential to develop an engineered strain of this kind of compound. Helvolic acid was also tested for the activities of phytopathogenic fungus, and the result was not clear.

Characters of plankton community metabolism of Daya Bay were studied using data collected in August 2016 and January 2017. The possible effects of nutrients input were discussed to understand the response mechanism of plankton to warming and eutrophication based on simulation experiments. The results indicated that both GPP (gross primary production) and CR (community respiration) were influenced by warming and nutrients input, and response of GPP to environment was seriously sensitive. The impact of GPP on nutrients input was more remarkably than that of temperature, except for being significantly inhibited in early cultured stage (24 h) with extremely high temperature conditions. In winter, both GPP and CR were significantly affected by the warming effect (p<0.05). Overall, both warming effect and nutrients input could affect carbon metabolism of plankton community which would lead to the declining of marine ecosystem stability, thereby affecting marine ecosystem stability and biodiversity and quality of marine ecological environment and fishery resource output.

Sebastiscus marmoratus as a marine economical teleost, research on the development of the larvae and juveniles of this species become important. In this study, the developmental characteristics of digestive system in S. marmoratus from 0 to 50 days post-parturition (dpp) were described by the method of tissue sectioning technique, HE (hematoxylin-eosin) staining and histochemical staining. The results showed that the initial digestive system appeared to have a differentiated buccopharyngeal cavity after parturition. At 2 dpp, the larvae began feeding, and the digestive tube opened to the outside initially, and the larvae entered the endo-exotrophic period. The pyloric caeca appeared at 3-4 dpp, while 5~6 mucosal folds appeared in esophagus, and five mucosal folds appeared in stomach and hepatic cell mass grew. At 5-6 dpp, the yolk sac was completely absorbed, meaning the larvae began getting into exotrophic period Ⅰ (without a functional stomach). Meanwhile, goblet cells were observed in esophagus, and intestine can be divided into promesenteron and hindgut. At 10-14 dpp, circular layers of striated muscle were obviously observed and 7-12 mucosal folds appeared in esophagus; stomach had a basic structure, brush border became clear and there were a few hepatic sinusoids in a bigger liver, which was good for the digestion and absorption of exogenous food. At 28-30 dpp, the gastric glands and gastric pits appeared, which was the signs of the juvenile stage. With the increase of the number of islet cells and zymogen granules, the digestion was greatly improved. At 47-50 dpp, the digestive system gradually improved as a functional and structural one, which resembled that of adults. These results showed that the development of the digestive system in S. marmoratus started early like other ovoviviparous teleosts and was relative with the improving function of its digestion.

Based on the survey in May, August and November 2016 and February 2017, the effects of natural and anthropogenic factors on macrozoobenthic community structure in the intertidal zone of Fangchenghe Estuary of Guangxi, China were studied. A total of 252 species belonging to 10 phyla of intertidal macrozoobenthos were collected, among which Mollusca, Arthropoda and Annelida were richer in species abundance. Cerithidea cingulata, Ruditapes philippinarum, Mictyris longicarpus, Batillaria zonalis, Cyclina sinensis, Laternula nanhaiensis, Meretrix meretrix, and Gelolna coaxans were ranked as the top eight dominant species in this study area through the whole year. The annual average density and biomass of the study area were 203 ind?m^-2 and 276.58 g?m^-2, respectively, in which Mollusca occupied 69.58% and 83.73% to the total, respectively. ANOVA showed that salinity and sediment type factors had significant influences (p<0.05 and less) on macrozoobenthos density, biomass, species diversity H′, Richness d, Evenness J, and quadrat-based species abundance, while season and tidal zone factors had very small influences (p>0.05) on them. Salinity had larger influences on density and biomass than sediment type did, while sediment type had larger influences on species diversity H′, Richness d, Evenness J, and quadrat-based species abundance than salinity did. Both clustering analysis and multidimensional scaling analysis obtained the same results that the 21 sampling stations could be divided into three groups, basically owing to the effects from salinity and sediment type. The status of diversity index H′ showed that in general the intertidal macrozoobenthic communities were under middle-level fluctuation. Comprehensively, three factors, i.e., salinity, sediment type and anthropogenic fluctuation, played combined roles on the spatial distribution pattern of macrozoobenthic communities in the intertidal zone of Fangchenghe Estuary.

Myostatin is an important member of the transforming growth factor (TGF) family that functions to regulate muscle development and growth in animals. It has become one of the most important target genes for genetic improvement of the production of farmed animals. The purpose of this study was to analyze correlation between single nucleotide polymorphisms of the myostatin gene and growth traits of the Haliotis diversicolor supertexta, which is an important aquaculture shellfish. The single nucleotide polymorphisms of the myostatin gene (Hs-MSTN) of H. diversicolor supertexta were identified by direct sequencing of PCR products, and association analysis of SNPs with H. diversicolor supertexta growth traits and Hs-MSTN expression level. Nine SNPs were identified in cDNA of Hs-MSTN, including four synonymous mutations. The associations of these SNPs were analyzed with H. diversicolor supertexta growth traits, including shell length, shell height, and body weight. The g909C>T SNP locus was found to be associated with shell length, shell height, and body weight. The TT type H. diversicolor supertexta showed significantly higher traits values than those of TC and CC types in body weight, and the TT type H. diversicolor supertexta also showed significantly higher traits values than CC type in shell length and shell height (p<0.05). On the contrary, Hs-MSTN transcripts in the musle of those of TC and CC types significantly more than in that of TT type (p<0.05). The results suggested that Hs-MSTN might regulate the addutor musle growth negatively, and SNP g909C>T could be used as a candidate marker for slective breeding of H. diversicolor supertexta.

In this paper, we review latest research on the Zhongnan-Liyue Fault Zone (ZLFZ), and then analyze the spatial distribution and tectonic deformation feature of the ZLFZ based on the geophysical data including topographic, seismic, gravity, and magnetic data. The results show that the ZLFZ in the South China Sea Basin has obvious north-south segmentation characteristics. The north section, which is between northwest sub-basin and east sub-basin, is a NNW trend narrow zone with a width of ~16 km from (18°00'N, 115°30'E) to (17°30'N, 116°30'E). The south section, which is between southwest sub-basin and east sub-basin, is a NNW trend wide zone with a width of 60~80 km from the east of the Zhongsha Bank to the west of the Liyue Bank. The main fault of the ZLFZ is NNW trend along the seamounts’ ridge of Zhongnan. The ZLFZ of transition region is NNE trend from the north section to the south section. On the eastern and western sides of the ZLFZ, the sub-basin’s sedimentary thickness and oceanic crust thickness are obviously different. We speculate that the ZLFZ plays an important role in the geological structure of sub-basin. According to the change of crustal structure, we suspect that the ZLFZ is at least a crustal fracture zone.

Based on analysis of the seismic images from prestack depth migration, combining previous results inverted from geophysical data, e.g., gravity and magnetic inversions and so on, we investigate the structure of the northeastern Zhongsha Trough Basin in the South China Sea. The results indicate that the Cenozoic strata are developed with a thickness of 1500~2500 m, and the stratum velocity is 1500~3500 m·s^-1. There is no Mesozoic sedimentary layer. The base of the basin could be seamount, Precambrian bedrock, or magma uplift. The abundance of Cenozoic terrigenous marine source rocks, the thick layer of the Cenozoic strata, and well-developed basin depressions and faults all suggest that the northeastern Zhongsha Trough Basin has a certain potential for oil and gas exploration.

Intra-seasonal variability (ISV) of sea level anomalies (SLA) and their propagation features in the northern South China Sea (NSCS) are investigated using 25-year (1993-2017) satellite observations. The standard deviation of intra-seasonal SLA reveals that larger ISV exists in the northeastern South China Sea along the continental shelf/slope (200~2000 m) where it extends southwestward from Taiwan to Hainan. The ISV of SLA exhibits obvious seasonality, being strong in winter and weak in summer. By using Complex Empirical Orthogonal Function (CEOF) analysis, the spatial pattern and temporal variability of the ISV, as well as their inter-annual modulation, are studied. We find that there are mainly two types of ISV pattern, showing great agreement with eddy activities in the NSCS. The ISV of SLA is also modulated by seasonal and inter-annual variation. The first mode of CEOF indicates southwestward propagation of the ISV from southwest of Taiwan to east of the Xisha Islands, being especially strong in winter. The second mode of CEOF reveals two westward ISV regions: southwest to Taiwan and south to the Dongsha Islands. The statistical analysis for the seasonal variation of mesoscale eddies indicates that the CEOF results are consistent with the distribution of mesoscale eddy activities in the NSCS.

By using various satellite remote sensing data and statistical analysis method, the contribution of typhoons in summer (from June to September) to the precipitation and freshwater flux in the South China Sea (SCS) and their possible influences on circulation anomalies in the SCS in the past 17 years (2000-2016) were studied. The main conclusions are as follows. Typhoon is one of the crucial factors that impact the precipitation in both northern and middle SCS, and the daily mean precipitation can be increased by 12 mm, which accounts for half of the daily mean rainfall in the SCS during summer. Besides, there are significant differences in the location and intensity of the rainfall distributions between the Northwest Pacific Ocean typhoons (NWP TYs) and SCS typhoons(SCS TYs). In summer, the saline circulation in the SCS induced by freshwater flux shows a weak cyclone that centers in the southwestern part of Hainan island with its magnitude of about -0.15 Sv, which is approximately 10% of wind-induced circulation (about -1.5 Sv) during the corresponding period. Precipitation induced by typhoons can intensify cyclonic saline circulation in the northern-central part of the SCS in summer. And the intensity of the saline circulation caused by NWP typhoons is stronger compared to that by SCS typhoons.

In this study, the data of tropical storms, CFSR gridded wind during 1949~2014, and Pearl River discharge were used to analyze wind forcing and runoff forcing on the Pearl River estuary (PRE) under tropical storm. The results show that the wind and runoff forcing varied with location and strength of the storm, and can be classified into four types: storm I with medium wind and runoff forcing on PRE, storm II with medium wind and high runoff forcing, storm III with strong wind and medium wind, and storm IV with strong wind and high runoff forcing. According to the selected moderate-resolution imaging spectroradiometer (MODIS) imaging with fine and no cloudy during tropical storms in South China, existing empirical formula between the water reflectance of MODIS band 1 and suspended sediment concentration (SSC) was used to retrieve the surface SSC in the PRE during storms, and the corresponding spatial diffusion of SSC was studied. We find that under four types of storms with different wind and runoff forcing, the responses of SSC in the PRE were different. The SSC was low under storm I, and suspended sediment diffusion was mostly controlled by tidal current. Under storm II, the higher SSC was shown in the Modaomen Estuary shoal and Lingdingyang west shoal than the other areas, which was mostly transported southwesterly. Under storm III, the distribution and diffusion of suspended sediment were influenced by the dominant storm wind, so that under strong NE wind, Lingdingyang west shoal sediment was resuspended by relatively larger waves for the largest wind fetch in the Lingdingyang estuary, higher SSC was presented and transported to the southwest under longshore current. The response of the PRE to storm IV was that the water body was muddy and the SSC was high in the whole PRE than under normal condition; and under southerly storm wind, the high SSC was diffused to the east

Suspended sediment concentration (SSC) in the Pearl River Estuary (PRE) during 2003-2015 was studied based on Moderate Resolution Imaging Spectroradiometer (MODIS) Level-1B product and in-situ measurements. The data were further used to analyze quantile trends and corresponding influence factors. The results showed that the SSC in the PRE displayed a decreasing trend, with an averaged SSC reduction rate of about1.03 mg·L ^-1·yr ^-1. The SSC in the regions near the river outlets and northeast part of the estuary suffered from much stronger decreases, which could be up to 4.0 mg·L ^-1·yr ^-1 during 2003-2015. Decreasing rate in high SSC were generally larger than those in low SSC, with a marked spatial difference. Low percentile of the SSC suffered from a stronger decline in the regions north of Qiao Island, with an increase in the variance of the distribution, while remarkable trends of high percentile of SSC occurred in the Humen outlet, northeastern coast of Longxue Island and regions near the East Channel, with corresponding decreases in the variance of the distribution. The quantile trends in the PRE were influenced by many factors. The seasonal variation of dam-induced reduction of the sediment load into the PRE contributed to most of the low-percentile SSC decreases north of Qiao Island. The subaqueous topographic change in the PRE induced by human activities dominated the high-percentile SSC trends in the Humen outlet, northeastern coast of Longxue Island, southern West Shoal, and regions near the East Channel. The decrease of the wind speed over the PRE also affected the high-percentile SSC trend in the southern West Shoal by weakening wind mixing in the boundary layer.

Based on the sea surface salinity data from 1999 to 2010 simulated by the high-resolution Finite-Volume Community Ocean Model (FVCOM), the seasonal and interannual variability of river plume in the Pearl River Estuary was analyzed and the main dynamic factors related to the variability were also discussed in combination with Empirical Orthogonal Function (EOF) analysis in this study. The field observation data during the simulation period were used to verify the simulation results for the 12 years, and the verification results showed that the model had higher accuracy and simulated the extension and variability of the plume fairly well. The simulated results showed that the plume exhibited significant seasonal variability. Affected by the high river discharge and southwesterly wind, the summertime plume exhibited a bidirectional structure with the plume extending westward attaching to the coast and eastward detaching from the coast. The extension area of the summertime plume was the largest. In winter, the river discharge attenuated to a minimum and the wind field changed into strong northeasterly wind. Consequently, the plume was squeezed to the western coast tightly to form a narrow band with the smallest extension area. The spring and autumn periods were transitional seasons, and the plume in these two seasons exhibited westward alongshore spreading. The summertime plume exhibited significant interannual variability with three main patterns, namely, the eastward extension dominated, approximately symmetric extension and westward extension dominated. In spring, the interannual variability of the plume was followed by that in summer and the variability mostly occurred in the western region and river estuary. The interannual variability in autumn and winter was not significant, especially in winter. The first EOF mode could explain 91.2% of the total variance, corresponding to the change in river discharge. The second EOF mode could explain 4.1% of the total variance, corresponding to the change in prevailing wind.

As global warming intensifies, the intensity of typhoon and the number of powerful typhoons have been increasing, which exacerbate the changing situation of salty tide disaster in the Modaomen Waterway. A three-dimensional baroclinic model was applied with SCHISM (semi-implicit cross-scale hydroscience integrated system model) in the Modaomen Waterway to analyze the effect of typhoon path on saltwater intrusion. Taking Typhoon Nesat (the west-path typhoon) and Typhoon Usagi (the east-path typhoon) as examples, different dynamic responses of saltwater transport and stratification were revealed. The east-path typhoon led to the set-down of coastal sea level, which increased the oceanward advective flux. However, the west-path typhoon led to the set-up of coastal sea level, which promoted the oceanward advective flux landward and caused more serious saltwater intrusion. Apart from the effect on coastal sea level, typhoons also cause strong local winds, which have important influences on velocity field and saltwater transport. The up-estuary local wind caused by the west-path typhoon tended to reduce stratification and increase the oceanward advective flux. However, the down-estuary local wind caused by the east-path typhoon tended to enhance stratification under moderate wind, but it reduced stratification when the wind stress increased.

Haiou Sandbody (HS) is a characteristic deposition body in the Pearl River delta. Based on the borehole data and the long-term morphodynamic model, the formation and evolution of the HS were studied. The bottom-up sedimentary sequence of the HI during Holocene is river facies, estuary shallow sea facies and delta facies. Since the maximum of the Holocene transgression, Humen tidal current and northeast-southwest tidal current have been the main forces influencing the formation and evolution of HS. From 6000 to 2500 a BP, due to the influence of the northeast to southwest fluctuating tide, the middle and northern parts of HS have been in a scour and non-sedimentary state. From 2500 to 1700 a BP, with the development of Panyu Plain, the northeast-southwest fluctuating trend gradually weakened, and the HS entered a rapid sedimentary period, with the mean deposition rate of about 15 mm·a ^-1. Between 1700 and 600 a BP, with the formation of the Shawan channel, the middle part of HS developed rapidly. To about 600 a BP, HS basically formed a dew surface.

Coralline algae are important functional group in the coral reef ecosystem. This study was carried out by a series of line transects run underwater with SCUBA apparatus from the reef flat to a depth of 9 m in each of the 11 research stations within the Sanya Coral Reefs in 2010. Among the inshore sites and the offshore sites of Sanya reefs, species composition and abundance of coralline algae were examined in relation to environmental factors. A total of 25 species belonging to three families and 10 genuses were identified, with the family Corallinaceae dominated in the study area. The eight dominant species were Amphiroa ephedraea, Mesophyllum simulans, Neogoniolithon fosliei, M. mesomorphum, Pneophyllum conicum, Porolithon onkodes, and Hydrolithon boergesenii. The sampling stations were divided into inshore type and offshore type based on the results of multivariate statistical analysis. The coralline algae species at the inshore sites were mainly turbidity, deposition rate (0~63 μm) and suspended solids (SS) tolerance species, while the species at the offshore sites were mainly light-dependent and sediment sensitive species. The results of community similarity analysis based on species composition and abundance of coralline algae showed the significant spatial variability. The correlation analysis between biotic and abiotic variables indicated that the best 2-variable combination (turbidity and salinity) showed a significant effect on the pattern of coralline algae assemblages between the two types of research sites in Sanya reefs. The living cover of coralline algae showed that deeper water is higher than that in shallow water due to the different degree of disturbance at the same study sites. This result suggests that physical disturbance, either natural or man-made, is a more important factor in regulating the coralline algae community structure within the coral reef distinct zone of Sanya.

RETRACTED： http://www.jto.ac.cn/CN/10.11978/2018084R

Oithona is one of the most abundant species of small and medium zooplankton in the ocean, and plays an important role in marine biogeographic genetics and ecology research. In this study, we employed 28S rDNA to analyze the population genetic structure and haplotype pattern of the most common species (Oithona setigera) in the South China Sea. A dataset of 792 bp in length sequences was obtained. The average contents of G+C (58.2%) were significantly higher than those of A+T (41.8%) in the fragment. A total of 28 haplotypes were defined from 186 individuals, of which the dominant haplotype H10 was found in 21 populations. The largest distance between two sampling sites harboring this haplotype is more than 1000 km, indicating Oithona setigera can achieve long distance disperse and be affected by ocean currents. The Mantel test showed that there was no linear correlation between the genetic distance and geographical distance (R= -0.04615, P=0.678); the RDA (redundancy analysis) results indicated space factor significantly affect the population genetic structure rather than environmental factors. The population genetic structure of Oithona setigera may be caused by colonization events followed by demographic expansions.

In this study, we investigated the metabolites from coastal mud-derived fungus WH7-2 by using the quorum sensing inhibitory (QSI) activity-oriented approach. The strain WH7-2 was identified as F. solani by analyzing its morphological characteristics and internal transcribed spacer (ITS) sequence. Chemical investigation of the rice fermentation product led to the isolation of 11 compounds. Their structures were elucidated as (2E, 5E)-3, 5, 7-trimethyl-2, 5-octadienoic acid (1), mixtures of unsaturated fatty acid ester (2, 3 and 4), 3-methyl ether fusarubin (5), Anhydrofusarubin (6), (22E)-5α, 8α- epidioxy-ergosta-6, 22-diene-3β-ol(7), (22E)-5α, 8α-epidioxy-ergosta-6, 9(11), 22-triene-3β-ol (8), 3β-hydroxycholest-5-en-7-one(9), 6β-hydroxy-cholest-4-en-3-one(10), and (22E)-cholest-5, 22-dien-3β-ol(11). All compounds were evaluated for their QSI activities, and only the mixtures of unsaturated fatty acid ester (2-4) exhibited QSI activity. All the compounds except 5 and 6 were first reported from F. solani.

The South China Sea is the largest marginal sea in the northwestern Pacific and the key channel connecting the North Pacific and northern Indian Ocean. When the Kuroshio flows northward along the Philippine Islands, signals from the western Pacific are transmitted to the South China Sea through the Luzon Strait, thus affecting the hydrodynamic environment of the South China Sea. We analyze the spatial distribution and low-frequency variability of subsurface salinity in the South China Sea, and try to explain the relationship between the subsurface salinity in the South China Sea and the Pacific Decadal Oscillation (PDO); we also explore the change of the subsurface salinity in recent years. The results are as follows. 1) Driven by the subsurface cyclonic circulation, subsurface salinity at about 24-26 σ_θ decreases gradually from north to south counterclockwise starting from the Luzon Strait. 2) The low-frequency variability of subsurface salinity is significantly correlated with PDO. When the PDO is in the positive phase, the westward transport in the Luzon Strait is strengthened and the subsurface salinity increases. When the PDO is in the negative phase, the westward transport in the Luzon Strait is weakened and the subsurface salinity decreases, and the salinity change is directly affected by the horizontal circulation. 3) In recent years, the subsurface salinity has shown a trend of refreshing from 2006 to early 2014, and then increasing from 2014 to early 2017, lagging behind the PDO by about 10 months. Since 2017, the salinity decreased again.

In the context of global warming, the 2015/2016 extreme El Ni?o event received much attention. This event was a mixture of central Pacific (CP) and eastern Pacific El Ni?o. Our study shows that both the westerly wind bursts and the North Pacific Meridional Mode contributed to the generation of this event. By comparing the 1997/1998 event, the 2015/2016 event and the CP event, the 2015/2016 event occurred in the warm background and shared similar development pattern with the CP event. What’s more, the rapid decline of sea surface temperature anomaly in the 2015/2016 event was related to the continued easterly anomalies and the weakened zonal current advection in the eastern equatorial Pacific. Compared with the 1997/1998 event, the ocean dynamic adjustment of the 2015/2016 event was weak, which was mainly reflected by weaker thermocline feedback and its associated fluctuations near the equator. Moreover, the zonal advection feedback was more efficient than the thermocline feedback, and the atmospheric forcing and its anomalous values in the central equatorial Pacific were larger. In addition, during the 2015/2016 event, the changes of the upper-ocean heat content in the equatorial region and the near- equatorial region were basically negatively correlated, and the changes were relatively synchronous. In the decay phase, the loss of ocean heat content mainly occurred in the 5°S-5°N region with significant heat transport to the higher latitudes.

Mixing is a ubiquitous motion in the ocean, which plays an important role in climate change and matter distribution. Seismic Oceanography is a new discipline in recent 10 years; it has been widely applied to Physical Oceanography, because it has the advantage of high spatial resolution. Seismic reflection data were used in this study, along with slope spectral method. We obtained the dissipation rate and diffusivity of turbulence interval and internal wave interval respectively in the Kuroshio (located in the east of the Luzon Strait). The results show that the average dissipation rate from 200- to 800-m depth in this profile is 10 ^-7.0W·kg ^-1, and the average diffusivity is 10 ^-3.3m ²·s ^-1, which is about 1-2 order of magnitude higher than the average value in the ocean 10 ^-5.0m ²·s ^-1. This result is consistent with previous mixing observations in the Luzon Strait. There is a big difference in diffusivity spatial distribution between turbulence interval and internal wave interval: the region where strong current occurs is consistent with that of high turbulence diffusivity in the profile, from which we can infer that this place may be the periphery of mesoscale eddy; its sub-mesoscale instability can strengthen the destabilization and then lead to strong mixing. The high internal wave diffusivity appears near the Luzon Arc, which indicates that the internal wave breaking occurs when it meets the island arc, leading to strong internal wave mixing.

Coralline algae are a group of calcified red algae of importance in many marine ecosystems, with significant roles in primary productivity and ecological functions, and are increasingly a focal group for research. Globally, species description and distribution of coralline algae are being gradually resolved, but within China, there is a lack of a national-scale summary and there is an urgent need to update knowledge of species diversity. This lack of background information seriously hinders national programs of research and conservation for coralline algae. In this paper, we analyze and summarize the state of knowledge on the diversity and distribution of coralline algae in China. Although a total of 155 species of coralline algae have been recorded in China, combining synonyms reduces this count to 105 species; they belong to 10 families and 26 genera, and account for 15% of accepted coralline algae species worldwide. The distribution of coralline algae ranges from the Bohai Sea to the South China Sea, showing features typical of distributions across tropical and subtropical regions. Relatively few species have been recorded from Liaoning, Shandong, Zhejiang, Fujian, Guangdong, and Hong Kong (less than 20 species in each region), while more species have been recorded for Taiwan, Hainan Island and Sansha regions (more than 30 species in each region). This study provides a good reference for determining species and distribution characteristics for coralline algae in China.

The energy accumulation and allocation of somatic and reproductive tissues in the medium form of male Sthenoteuthisoualaniensiswere were analyzed by using the technology of energy density determination combined with residual analysis. The results showed that the energy density of mantle, fins, arms, spermatophoric complex, and testis were 21.16±1.44, 21.98±1.51, 21.44±1.50, 20.83±1.70, and 21.41±1.70kJ·g ^-1, respectively. The energy density for tissue of mantle or spermatophoric complex varied significantly depending on sexual maturity stages, while there were no significant differences between sexual maturity stages for the tissue of fins, arms, or testis. The total energy accumulation for each individual was estimated at 299.31±90.81 kJ, and showed an increasing trend with body size growth. With regards to relative energy accumulation, the somatic tissues, including mantle, fins and arms, accounted for 95.31%~98.04% of the total energy accumulation, but decreased with maturation. The relative energy accumulation in reproductive tissues, being testis and spermatophoric complex, accounted for 1.96%~4.96% of the total energy accumulation, and increased with maturation, in which the maximum value was reached at stage V. The analysis of residuals of relationship between tissue absolute energy accumulation and mantle length, using Model II regression, showed a significantly positive correlation between somatic and gonadal tissues. This evidence suggests that there was no energy remobilization of somatic tissues to fuel reproduction during sexual maturation, and the mode of reproductive investment is more likely to be income breeding in the medium form of male S.oualaniensis. In this study, we preliminary established the progress of energy accumulation and its allocation in soma and reproductive organs for medium form of male S.oualaniensisin the South China Sea. These findings should assist future research on its reproductive strategy, as well as sustainable utilizationof this kind of resource in the area.

The gammarid Hyale grandicornis is a common crustacean species in macroalgae along the coastline of China, but the correlation between H. grandicornis and macroalgae is not well known. Two dominant macroalgae species found on coastal rocks of Daya Bay, the green algae Ulva lactuca and the brown algae Sargassum hemiphyllum var. chinense, were used in the experiments. H. grandicornis samples were found in the bush of two macroalgae canopies. The individual number, body size and weight of gammarid H. grandicornis population were higher in the bush of U. lactuca than in S. hemiphyllum var. chinense. The sex ratio and the proportion of females with eggs and the amount of juvenile of gammarid in bush of S. hemiphyllum var. chinense were larger than those in U. lactuca, whereas the body sizes of adults and females with eggs and the volume of eggs were smaller in gammarid from S. hemiphyllum var. chinense. Results demonstrate that the population distribution and production of gammarid H. grandicornis were different in the two macroalgae, which may be affected by the algal phenotype and habitat preference.

A conid species, Conus ferrugineus Hwass in Bruguière, 1792, was recorded from China for the first time based on specimens deposited in the Marine Biodiversity Collections of the South China Sea, Chinese Academy of Sciences, and on samples recently collected from voyages to the South China Sea. The specimens were collected from the Xisha Islands. The shell morphological features of this species were presented, as well as its habitat and distribution. C. ferrugineus is easily confused with its sympatric sibling species C. vitulinus Hwass in Bruguière, 1792. The most remarkable difference is its uniformly white aperture, in contrast to the violet to violet brown base of the aperture in C. vitulinus. The identification characteristics between them were also discussed and summarized in this paper.