The species in the family of Sesarmidae are among the species mostly difficult to be differentiated taxonomically in the Superfamily Grapsoidea because of their morphological similarity. The analysis of partial sequences of mitochondrial COI gene and 16S rRNA gene of 14 species in 8 genera of Sesarmidae for their molecular phylogenetics reveals that the percentages of sequence divergences of 14 species of Sesarmidae are from 5.7% to 14.5% and from 1.5% to 12.1%, both indicating that the species difference are significant. The phylogenetic trees show that the 14 species are separate and valid species and 4 species of Parasesarma and 3 species of Perisesarma are not 2 independent clades but clustered into 1 clade. Chiromantes dehaani and Sesarmops sinensis are clustered into one clade and then clustered with C. haematocheir into another clade, inconsistent with their morphological classification. The complicated molecular phylogenetic relationship among the species of Sesarmidae suggests that the species in the family of Sesarmidae might have polyphyletic origin, and their interspecific relationship or intergenus relationship need to be clarified.

Catch-MSY method can temporarily replace conventional stock assessment models in making management decisions for a data-limited fishery, even when only catch data are available. In this study, for the sensitivity analysis and assessment of the Indian Ocean blue marlin, we established 15 scenarios based on non-informative and informative prior distributions of the intrinsic growth rate r and carrying capacity K. Sensitivity analysis reveals a high negative correlation between parameters r and K, and the estimated maximum sustainable yield (MSY) increases with r. Sensitivity analysis shows that the length of catch time series has less influences on the results of the assessments, but the assessments are sensitive to catch data in the first and last year. The assessment results reveal that the status of total biomass is optimal, with the ratio of B ₂₀₁₅ to B _MSY higher than 1. Exception is only two scenarios, the exploitation status under the other scenarios would be overfishing, since all the ratios of F ₂₀₁₅ to F _MSY would be higher than 1. Projections of future stock status show that, to attain the objective of maintaining B/B _MSY>1 with a probability of higher than 50% in the next 10 a, the catch would have to be reduced to 90% (13 860 t) of the current level. Considering that the catch-MSY method is conservative under data-limited conditions, maintaining 100% to 110% (15 400–16 940 t) of the current catch could achieve the objective of maintaining B/B_MSY >1 with a probability of higher than 50% in the next 5 a.

In order to further study the metamorphosis development and growth characteristics of the hybrid offspring of Epinephelus lanceolatus♀×E. tukula♂, we measured embryonic development time, fertilization rate, deformity rate, hatching rate and growth traits (full length, body length, height and anal front) of the hybrid offspring and E. lanceolatus. We also observed the absorption process of yolk sac and oil globule, the growth and contraction of the second dorsal spine and pelvic fin spine, and the changes of eye diameter and oral fissure during embryonic development of hybrid offspring. Statistical analysis of the data was performed. The results show that the hybrid offspring and E. lanceolatus complete embryo development at 21 h 24 min and 21 h 32 min at 28℃, respectively; the fertilization rate, deformity rate and hatching rate of hybrid offspring are 89.09%±0.08%, 35.16%±5.05% and 62.59%±10.70%, respectively, no significant difference is shown compared with that of E. lanceolatus. According to the morphological changes of yolk sac, second dorsal spine, pelvic fin spine, scales and body color, the post-embryonic metamorphosis is divided into early larvae (0–6 d after hatching), late larvae (7–34 d after hatching), juveniles (35–46 d after hatching) and juvenile fish period (47–86 d after hatching). The growth of the early larvae is slower, while the growth of the larvae to the juveniles increases gradually. At 86 d after hatching, the body lengths of the hybrid offspring and E. lanceolatus reach (60.80±0.50) cm and (51.80±0.47) cm, which indicates the growth of the hybrid offspring is significantly faster than E. lanceolatus (P<0.01). During embryo development, the yolk sac consumption is 29.45%, the oil ball consumption is 20.75%, and the yolk sac consumption is the fastest at 1 d after hatching, reaching 58.70%. The oil globule consumption is the fastest at 3 d after hatching, reaching 32.08%, and the yolk sac and oil globule of the larvae are basically absorbed at 5 d after hatching. The lengths of the second dorsal spine and pelvic fin spine reach the longest of (8.15±0.02) mm and (5.80±0.10) mm at 29 d after hatching respectively, and they completely degenerate at 47 d after hatching which marks the completion of metamorphosis. The eye diameter of the larvae is (0.16±0.01) mm at 1 d after hatching, which increases by 22 times at 86 d after hatching. The length of oral fissure is (0.09±0.02) mm, and it increases by 99 times at 86 d after hatching. The results show that the hybrid offspring of E. lanceolatus♀×E. tukula♂ develops normally, and the hybrid offspring shows a significant growth advantage comparing with its female parent. This study provides rich data for seed cultivation, development research and variety improvement of the hybrid offspring.

Previously, it was a broad consensus that transparent exopolymer particles (TEP) resulted in carbon flux output to the seabed due to its unique aggregation effect. Recently, some studies have shown that TEP could be retained in the water column and even ascend to the surface layer, which profoundly contributed to the elevated TEP concentrations and decreasing of air-sea carbon fluxes in the Surface Micro-layer (SML). The sinking or ascending of these TEP originated aggregates was finally depended on its density. TEP and further aggregated with other micro-particles became the surface-active substances in the SML, produce a thin layer film at the ocean-atmosphere interface, will heavily affect the exchange fluxes of sea-air CO₂ and further the global climate changes.

In order to study the distribution of gas hydrate stable zones (GHSZ) in the Huaguang Sag of Qiongdongnan Basin, the important factors affecting GHSZ's thickness are quantitatively studied, including hydrostatic pressure, bottom water temperature, geothermal gradient and gas source composition. Then, it analyzes that the thickness distribution of the present methane GHSZ in Huaguang Sag. Finally, based on the historical evolution process of above various factors, the evolution of gas hydrate stabilization zone since 1.05 Ma BP in this area is preliminarily discussed. The results show that: (1) the gas source composition and seabed temperature have a great influence on the GHSZ in the study area, and the thickness of GHSZ has a good linear negative correlation with seabed temperature; (2) the temperature and pressure conditions for gas hydrate formation are available in the Huaguang Sag of Qiongdongnan Basin, where water depth is more than 600 m, the thickness of the hydrate stability zone is more than 100 m; the thickest GHSZ is located in the northwest of the study area, with a maximum thickness of more than 300 m; it is a favorable hydrate exploration area; (3) the methane GHSZ has gone through stable stage, relatively quick incrassation, gently changing stage, and quickly attenuating and recovery stage since 1.05 Ma BP. There is a good superposition relationship between the pockmark group and the sensitive area of GHSZ. Combined with previous research results, it is concluded that their formation is related to the decomposition and release of natural gas hydrate.

This study documents the data of fish species systematically collected in the off southern Zhejiang, East China Sea, from November 2015 to August 2016, according to Nelson’s classification system and analyzed the diversity at different taxonomic levels. The inclusion index at taxonomic level (TINCL _i ), taxonomic diversity (the average taxonomic distinctness △⁺ and the variation in taxonomic distinctness ∧⁺) are used in this study. The results show that the fish species in the waters belonged to 18 orders, 78 families, 130 genera and 182 species. It is concluded that the number of species in spring (104 species) is larger than that in autumn (103 species) and winter (93 species), while the smallest number occurs in summer (88 species). Analyzed by TINCL _i , the average numbers of (families, genera, species), (genera, species) and (species) per order, family and genus are (4.33、7.22、10.11), (1.67、2.33) and (1.40). The △⁺ and ∧⁺ in the off southern Zhejiang, East China Sea, are 62.9 and 77.0, respectively. The △⁺ in our study area is less than those in the high latitude areas, such as the Yellow Sea and Bohai Sea (66.4), the coastal waters off Shandong (66.1), and is greater than those in the lower latitude waters including the Nansha Islands (56.6), the Xisha Islands (60.2) and the Dongsha Islands (55.2). The results above indicate that the △⁺ decreases with latitude. This study analyzed taxonomic diversity of fish species in the off southern Zhejiang, East China Sea, which can provide reference for the exploitation and conservation of fish species in local waters.

Selective chemical extraction method was utilized to fractionally extract platinum group elements (PGE) in cobalt-rich crusts from Caiwei Seamount in the Pacific, and PGE contents were determined by inductively coupled plasma mass spectrometry (ICP-MS). Occurrence phase analysis results in cobalt-rich crusts show that the PGE enrichments in different phases conform to the following order: iron oxide phase, residual phase, manganese oxide phase, carbonate phase, adsorbed phase. PGE in the new non-phosphate layers and the old phosphate layers are mainly enriched in the iron oxide phase, with the enrichment ratio from 59.26% to 82.19%, and the phosphate in residual phase has certain enrichment ability for PGE, with the enrichment ratio from 17.23% to 35.37%. Meanwhile, occurrence phase analysis results in different geological bodies show that the PGE enrichment in cobalt-rich crusts and seamount nodules is mainly affected by iron oxide phase and residual phase. In addition, the enrichment mechanism of PGE in cobalt-rich crusts is presumed to the iron oxide/iron hydroxides colloid particles adsorption, and the soluble $ {\rm PtCl}_4^{2-}$ in seawater is adsorbed into the iron oxide phase, so PGE are enriched in cobalt-rich crusts.

In order to further explore the changes in relationships between seasonal succession of zooplankton and temperature-salinity in coastal East China sea, zooplankton survey data of three voyages in May (spring), August (summer) and December (winter) of 2013 were analyzed. Redundancy analysis model (RDA) was used to analyze the relationship between the changes of the dominant species and temperature-salinity, then the general algebraic modeling system (GAMs) was applied to analyze the relationship between temperature-salinity and parameters of the biological diversity. Results show that the dominant species’ succession changes seasonally from spring (2 kinds) to summer (10 kinds), then becomes 5 kinds in winter. Dominant species and the ecological groups are relatively single in spring and winter, but rich in summer. The temporal and spatial distribution of dominant species are the results of a comprehensive multi-level of environmental factors. For example, Calanus sinicus positively relates to surface salinity and bottom salinity in spring, negatively relates to surface temperature and bottom temperature in summer, positively relates to surface salinity in winter. Muggiaea atlantica presents better positive correlations with bottom temperature and bottom salinity in spring. What’s more, salinity is the key factor to determine the distribution of dominant species like warm water species and high temperature-salinity groups in summer, it also presents strong positive correlations. Labidocera euchaeta and Aidanosagitta crassa have strong negative correlations with surface temperature in winter. Shannon-Wiener diversity index negatively correlates with latitude in spring and winter. Biodiversity parameters are significantly affected by the temperature and salinity, but the influence presents differences seasonally.

The green tide occurred in the South Yellow Sea for 10 a from 2008 to 2017, affecting aquaculture, tourism and the safety of shipping in surrounding coastal cities. Studying the progress of the green tide and their influencing factors are of vital significance for understanding the distribution characteristics of the green tide in the South Yellow Sea and for preventing and controlling the green tide disaster. MODIS L1B data is used in this paper and normalized difference vegetation index is applied to extract related information of the green tide. According to the variation characteristics of the coverage area of the green tide, the whole progress of the green tide is divided into three stages: trigger stage, fast development stage and depletion stage. And the effects of sea surface temperature, precipitation and short-wave radiation on the variation of the green tide were analyzed. The results show that in the trigger stage, when the temperature is over 15℃, effective precipitation can stimulate the triggering of the green tide. The green tide can be detected by MODIS image within half a month following the effective precipitation. In the fast development stage, the sea surface temperature at the location of the green tide is 16–21℃, which is suitable for the rapid growth of the green tide. The solar short-wave radiation is concentrated in the range of 250～280 W/m², and the precipitation is important for the growth of the green tide during this stage. The peak coverage area of the green tide is low when precipitation is small, while the precipitation is extremely high in 2016 when the peak coverage area is the largest. During the depletion stage, the sea surface temperature rises to 22–26℃. When the green tide disappears, the average sea surface temperature exceeds 26℃, and the highest temperature reaches 27.48℃. The high sea surface temperature is one of the main factors for the demise of the green tide. The solar short-wave radiation is concentrated at 240–260 W/m², which is slightly lower than that in the fast development stage. The precipitation is relatively sufficient in this stage and no longer affects the growth of the green tide.

Hydrothermal plume is an important symbol of hydrothermal activity. Seafloor polymetallic sulfide deposits are products of hydrothermal activity. At the present stage, seafloor polymetallic sulfide prospection and exploration in the mid-ocean ridges are mainly based on the detection of hydrothermal plume and combined with the comprehensive anomaly detection information to realize the breakthrough from the discovery of hydrothermal vents to the discovery of mineral deposits. Based on the hydrothermal plume as the research object, from the three aspects of near-bottom observations, dispersion mechanism and distribution characteristics, this paper summarizes the latest progress and aspects need to be improved of hydrothermal plume, and emphasizes the hydrothermal mapping as a prospective tool for seafloor polymetallic sulfide deposits in the mid-ocean ridges. Finally, this paper points out in conclusion that the spatial and temporal continuity, parameter diversification will be the development trend of hydrothermal detection, which will help promote understanding of hydrothermal plume distribution characteristics and will provide more detailed data to the study on the model of the hydrothermal fields.