Most marine invertebrates undergo planktonic and benthic stages during growth. As a marine economic shellfish and macrofouling organism, Mytilus coruscus has attracted widespread attention. To explore the interaction between marine bacteria and the mussel settlement, Pseudoalteromonas marina, which has a high inducing activity for the plantigrade settlement of the M. coruscus was chosen and the flagellin was extracted by acid hydrolysis ultracentrifugation. The impact of extracted flagellin mixed with agarose solution to on plantigrade settlement was tested directly. The P. marina biofilms treated with extracted flagellin were used to investigate the inducing capacity on plantigrade settlement. Changes in biomass, bacterial density and extracellular products of the biofilms were analyzed by confocal laser scanning microscopy. The results showed that the mixed gel containing P. marina flagellin and agarose significantly promoted the settlement of plantigrades. In other treatment, the flagellin-treated biofilms also had a high inductivity of plantigrade settlement. Biomass, bacterial density, membrane thickness, extracellular β-polysaccharide, lipid and protein contents all increased. The study reveals that flagellin can directly regulate the settlement of plantigrades and control the inductivity by changing the biological characteristics of the P. marina biofilm indirectly. The study is valuable for clarifying the interaction between bacterial flagellin and plantigrade settlement of the M. coruscus.

The foraging depth of yellowfin tuna (Thunnus obesus), which is primarily influenced by the vertical structure of the water temperature, has a significant effect on longline catch rates. Therefore, the generalized additive model (GAM) was applied to analyse the influence of subsurface environmental variables on the longline catch per unit of effort (CPUE) in the central and western Pacific. The results show that subsurface environmental factors have significant impacts on the spatial distribution of yellowfin tuna catches in longline fisheries. The longline CPUE for the yellowfin tuna in the tropical central and western Pacific rise rapidly after 2012. A high catch rate appears in the northern hemisphere during summer in the region near 10°S, 140°E. The upper boundary temperature and depth of the thermocline, the lower depth of the thermocline, the depth of the isotherm at 18℃, and the relative depth between △8℃ and the lower depth of thermocline greatly influence the longline fishing rate. These key environmental factors affect the tropical central and western Pacific yellowfin tuna longline catch. The CPUE increases as the temperature and the depth of the upper boundary of the thermocline increased. The strongly associated relationships between the upper boundary temperature and depth with CPUE were 27−28℃ and 70−90 m, respectively. High catch rates are observed when the lower boundary depth of the thermocline is from 250 m to 280 m. Then, as the lower boundary depth increased, the CPUE value quickly decreased. The effect of the 18℃ isotherm depth on the CPUE of longline fishing initially fluctuated and then increased. The nonlinear effects of the relative depth between △8℃ and the lower depth of the thermocline first decreased and then increased slowly. The strong associations between CPUE and the 18℃ isotherm depths and relative depth are at 230 m and 70 m, respectively. The catch rates reaches a maximum when the vertical habitat is compressed, making it consistent with hooking depth. The catch rates could be changed by adjusting the depth of hooks. The vertical habitat of tuna should be taken into account in fisheries stock assessments and fishing grounds analysis.

Speciation and distribution of phosphorus have a direct effect on the primary production and marine biogeochemistry. However, the complex current dynamics in aquatic critical zones such as large river delta and coastal area result in variable characteristics of the phosphorus speciation and distribution that need in depth study. The content, distribution and influence factors of total particulate phosphorus (TPP), particulate inorganic phosphorus (PIP) and particulate organic phosphorus (POP) in the suspended particulate matter (SPM) in the Zhejiang coastal area off Changjiang Estuary were discussed based on the investigation from April to May (spring), July (summer) and September to October (autumn) in 2016. The results showed that the content ranged from 0.13 μmol/L to 66.13 μmol/L, with an average of 3.35 μmol/L for TPP, from 0.03 μmol/L to 34.19 μmol/L with an average of 1.97 μmol/L for PIP, and ranged from 0.06 μmol/L to 31.94 μmol/L with an average of 1.39 μmol/L for POP. PIP was the dominant (52.3%) form of particulate phosphorus in the Zhejiang coastal areas. The percentage of TPP in total phosphorus ranged from 19.3% to 97.7% in spring for surface samples. The spatial distribution patterns of TPP, PIP and POP contents were similar in spring and autumn, decreasing from the inner bay to offshore areas. The content of TPP was higher in areas where the SPM was higher while PIP and POP showed a positive correlation with SPM, indicating an influence from terrestrial input. The regression coefficient and slope between POP and chlorophyll a were significantly higher than that of PIP in the area with salinity above 28 and SPM below 20 mg/L in spring, indicating contributions from phytoplankton to POP accumulation.

Based on the one-layer Boussinesq model with highest spatial derivative being 3, a numerical model is established for focused wave group. The numerical model is solved with predictor-corrector scheme in finite differential method. For time integration, a third-order Adams-Bashforth scheme and a fourth-order Adams-Moulton scheme are separately used in predicting stage and correcting stage. Firstly, the numerical simulations are carried out upon nonlinear regular wave evolution over a constant water-depth in a flume, and the computed results are compared with the semi-analytical solutions. The results demonstrate that the simulated surface elevations, the horizontal velocity and vertical velocity on the free surface can well match the related analytical solutions, while the agreement of the horizontal velocity profile under the crest becomes worse with the increase of water-depth, and the range of the model with respect to nonlinear horizontal velocity profile is for kh<3.5, which is similar to the range of the related linear model with respect to horizontal velocity profile. Secondly, the numerical simulations are conducted upon the nonlinear focused wave group evolution in deep-water. The linear wave groups are used as incident wave conditions. The laboratory experiments conducted by Baldock and Swan (1996) are used to examine the present model. Both the computed surface elevations and the horizontal velocity profile at the focused position are compared with the related experimental data. The results show that the agreement of the surface elevations is pretty good, while the agreement of the horizontal velocity profile is moderate. Finally, with the middle frequency being kept unchanged, the numerical simulations upon the maximum surface elevation and horizontal velocity under the crest are conducted with the variation of the range of focused wave period, the results show that both the crest and the horizontal velocity increase with the increase of the range of the wave periods.

Since 1950, the sediment load of the Changjiang River entering the sea has been stepwise decreasing. As the distal mud of the Changjiang River, whether the signal of “sediment load reduction” was recorded in the Zhe-Min coastal mud? If so, how to extract and interpret these sedimentary information? In order to discussing this scientific problem, 5 sediment cores were collected in the Zhe-Min coastal mud; in addition, high resolution grain size analysis (2 mm) was conducted, and four end members were obtained through end-member (EM) model decomposing. Combined with the analysis of the spatial discrepancy in provenance and hydrodynamics of the study area, the specific indicative significance of each EM was revealed: EM1 (with the modal grain size about 2 μm) is originated from extremely fine-grained sediment of the Changjiang River; EM2’s (with the modal grain size about 10 μm) origin is predominated by the Changjiang River, and small part is contributed by the middle and small sized rivers of Zhe-Min coast; EM3 (with the modal grain size about 80 μm) mainly consists of coarse-grain sediment might be provided by Taiwan Warm Current; EM4 (with the modal grain size about 200 μm) is also characterized by coarse-grain sediment, and may be contributed by the Changjiang River. Further analysis indicated that, the EM1 variation was in agreement with the sediment stepwise reduction of the Changjiang River; however, the response intensity gradually decreased from the north to the south. In addition, the hysteresis existed in response time, and the retardation time increased from 4−6 years in the north to 10−14 years in the south. In general, fine-grained sediment could better reflect the Changjiang River catchment change information, and response intensity exhibited significant difference in different areas of the Zhe-Min coastal mud.

In view of the effect of internal solitary waves on the seafloor when encountering the seabed slope during their travel, the dynamic response of different slopes to internal solitary waves should be different. This paper studies the dynamic response process of internal solitary waves of slopes with different angles by creating internal waves in a flume. The results show that the internal solitary waves passing over the shelf slope will cause the accumulation of excess pore water pressure in the slope sediments; under the same amplitude conditions, the dynamic response amplitude of the gentle slope sediments is larger than that of the steep slope sediments; as the amplitude increases, gentle slopes occur the degree of dynamic damage is greater than that of steep slopes; the accumulation and release of excess pore water pressure exist at the same time before the stability of slope sediments is destroyed, and the increase of the amplitude of internal solitary waves will aggravate the release of excess pore water pressure. The results will play a guiding role in the dynamic study of the failure of slope sediment under the action of internal solitary waves and the analysis of slope stability.

The sediments in the hydrothermal field received a large amount of hydrothermal input, and their mineral compositions and geochemical spatial distribution characteristics are effective indicators for polymetallic sulfide exploration. Due to gravity, sediments in the mid-ocean ridge area are mainly distributed in low-lying and flat terrain areas. In order to explore the influence of topographical factors on the distribution of sediments in the hydrothermal field, this paper proposes a prediction method of sediment distribution trend in seafloor hydrothermal field based on topography data through ArcGIS, and analyzes the topographic data of Dragon Horn area on the Southwest Indian Ridge, including the extraction gravity transport direction of sediment, the estimation of sediment accumulation amount, the extraction of submarine ditch valley and the division of sediment source area. By comparison and verification with the interpretation results of the seafloor camera data of the study area, we found that the prediction results are in good agreement with the actual distribution range of the sediments in the study area, indicating that this method can effectively indicate the distribution of sediments in the submarine hydrothermal field under the influence of terrain to a certain extent. This method has certain guiding significance for the exploration of submarine sulfide minerals, and could provides a reference basis for the setting of sampling stations for seafloor sediments and the delineation of polymetallic sulfide mineralization prospects.

Based on the CTD data from the 28th, 29th and 31st Chinese Antarctic Expedition cruises, we calculated dissipation rate of turbulent kinetic energy by using Thrope scale method, and analyzed the distribution characteristics of the dissipation rate and the structure of water masses in the Prydz Bay and its adjacent waters. Results show that the subsurface dissipation rate intensity of turbulent kinetic energy in the first two cruises reach maximum on the shelf break of Prydz Bay. Moreover, we compared the distribution of water masses among the three cruises and found intrusion of the modified circumplar deep water into the shelf happened on the 28th and 29th cruises. The the modified circumplar deep water could reach the depth of 100 m and 200 m on the cruise of 28th and 29th, respectively, and can extend southward to 67.5°S. Furthermore, the distribution of subsurface dissipation rate of turbulent kinetic energy on the shelf break of Prydz Bay are well related to the structure of local water masses. Therefore, the intrusion of the modified circumplar deep water into the shelf could induce instability of the local waters, promote water exchange and finally enhance local turbulent mixing.

The formation and evolution of the South China Sea is well recorded in the northern continental margin. But the discrepancies of the tectonic and sedimentary evolution between the west and east of the northern margin are still enigmatic. Several drilling and simulation wells with analogous geological setting are chosen from the deep water areas of the Zhujiang River Estuary Basin and the Qiongdongnan Basin. Based on backstripping and previous studies, high resolution sedimentation rates and subsidence rates are constructed. Results show that both two basins are characterized by analogous sedimentation rates and subsidence rates in the syn-rift stage, but significant discrepancies are revealed in the post-rift stage. Episodic sedimentary and tectonic evolution characteristics are revealed in the Zhujiang River Estuary Basin, sedimentation rates are characterized by “two rapid sedimentation periods and three slow sedimentation periods” and subsidence rates are characterized by “two rapid subsidence periods and one slow subsidence period”. But the sedimentation rates are characterized by “graben” style evolution, and the subsidence rates are characterized by “step-up” style evolution in the Qiongdongnan Basin. The “step-up” subsidence rates in the Qiongdongnan Basin might be controlled by activities of the Hainan mantle plume which moved northwestward derived from the dextral strike-slip of the Red River Fault. And it coincided with the magmatism and the subsidence rate in the northwest margin of the South China Sea. The distribution of the rapid deposition and accelerated subsidence in the Qiongdongnan Basin after 1.8 Ma BP could be mainly controlled by the meanwhile dextral strike-slip of the Red River Fault.

In recent years, several deep-water gas fields of Yinggehai Formation have been discovered in ultra-deep water area of Qiongdongnan Basin, showing a broad exploration prospect. However, the reservoir physical property prediction of the Member 2 of Neogene Yinggehai Formation have become increasingly prominent which seriously restricts the further exploration of oil and gas. Based on the regional geological data summarized by predecessors, combined with core, logging and three-dimensional seismic data, the third-order sequence framework of the Member 2 of Neogene Yinggehai Formation is established, and the provenance systems in the sequence framework and the sedimentary characteristics of gravity flow under its control are comprehensively analyzed. The results show that gravity flow sedimentary system mainly developed in Ⅱ2-ygh2c and Ⅱ2-ygh2b, and include three major provenance systems which are the south, the north and the axis. Different rovenance systems control the spatial distribution and sedimentary characteristics of gravity flow reservoirs. (1)The submarine canyons controlled by the south provenance are mainly filled by abyssal mudstone, while the canyons controlled by the north provenance are mainly filled with thick turbidite channel sandstone with fine porosity and permeability, which is a good reservoir. (2) The flood plain deposit affected by axial provenance can also be a good oil and gas reservoir because of its good physical properties. (3) The submarine fans controlled by the south provenance is characterized by thin sandstone with fine grain size and high argillaceous content. While the submarine canyons and fans controlled by the north and the axis provenance formed large scale sandstone with big thickness, coarse grain size and good reservoir physical properties, which are the most important high-quality gas-producing reservoirs of deep water area.