In order to find an effective way to reverse the decline in the health of the oceans, the United Nations has decided to launch the "United Nations Decade of Ocean Science for Sustainable Development" (hereinafter referred to as the "Ocean Decade") since 2021. The Implementation Plan of Ocean Decade, which has been aceepted by the United Nations General Assembly on September 31, 2020, outlines the Ocean Decade’s vision of “building the science we need and the ocean we want”, and sets out the outcomes, challenges and objectives of the Ocean Decade, as well as mechanisms for implementation, governance, coordination, financing, monitoring and review. Described by the United Nations as a “once in a lifetime” programme, the Ocean Decade is a comprehensive United Nations-sponsored capstone programme for Ocean Megasciences that will build stronger science and technology innovation-based governance system at the global and national levels by inspiring and driving change in marine science. This will profoundly change human cognition and behavioural patterns towards the oceans, profoundly influence and even guide the evolution of the marine order, and have a great impact on the overall layout of regional cooperation in the oceans. It is suggested that China, guided by the concept of the “Marine Community with Shared Future”, actively participate in the Ocean Decade as a core means of deepening its participation in global ocean governance, and establish the Ocean Decade National Committee as soon as possible, and develop a Chinese programme of action to advance the sustainable development of the oceans and seas together with the international community.

Himawari-8 is a new generation geostationary meteorological satellite launched by the Japan Meteorological Agency, and provides the important observation data for merging hourly sea surface temperature (SST). This paper uses the optimal interpolation method to provide the hourly Northwest Pacific SST based on the Advanced Himawari Imagery(AHI) SST, the Global Change Observation Mission-Water (GCOM-W1) Advanced Microwave Scanning Radiometer 2 (AMSR2) SST and North-East Asian Regional–Global Ocean Observing System (NEAR-GOOS) SST. The diurnal SST variation and the bias between multi-source SSTs are the two significant factors affecting the accuracy of hourly SST fusion products. In order to make full use of SST at the adjacent time and improve the accuracy, a diurnal variation model of Himawari-8 AHI SST is established by using the matchup data set, which contains simultaneous Himawari-8 AHI SST and European Centre for Medium-Range Weather Forecasts wind data at the same location. In addition, a bias correction method based on Poisson’s equation is applied to correct GCOM-W1 AMSR2 SST biases relative to the AHI SST. The experimental results show that the diurnal warming calculated by the hourly SST fusion product is closely related to sea surface wind speed, which indirectly confirms the accuracy of the hourly SST fusion products. The root mean square difference and bias between the hourly SST fusion product and NEAR-GOOS SST are 0.89℃ and 0.09℃, respectively. The results show that the hourly SST fusion product is basically consistent with the in situ SST.

The Okinawa Trough is an initial back arc basin developed on the continental crust due to the subduction of Philippine Sea plate under Eurasian plate. It is a natural laboratory to study the basin evolution, magmatism and crust-mantle interactions in the early stage of back arc expansion. Although a lot of investigations and research works have been done so far, there are still some controversial or urgent scientific problems, such as the genetic relationship between acid pumice and basic basalts in the trough, the control of tectonic background on magmatism in different sections of the trough, the characteristics of magma-derrived mantle, and the influence of subduction plate components (fluid + melt) on the mantle wedge, etc. On the basis of systematically collecting and sorting out (excluding some doubtful data) the major element, trace element (including rare earth elements) and Sr-Nd-Pb isotopic data of volcanic rocks in the Okinawa Trough, the author further confirmed the magma homology of acid pumice and basic basalt through systematic analysis of the data, and believed that the distributions of acid pumice and neutral andesite in the north and middle sections of the trough should be the reflection of regional rift at present, while the basic basalts widely distributed in the south section indicate that they are close to mature back arc basin in structural property. The volcanic magma source area of Okinawa Trough has the characteristics of enriched mantle II (EMII)-type Dupal anomaly, and the magma comes from the source mixed by end-member of prevalent mantle (PREMA) and EMII type mantle end-member, of which the ratio of EMII is about 15% and PREMA about 85%. The addition of fluid/melt from subducted Philippine Sea plate (subducted ocean crust or sediment) is the reason for the EMII type characteristics of magma-derrived mantle beneath the Okinawa Trough, which is different from the viewpoint that the Dupal anomaly originates from the interaction between crust and mantle.

The risk assessment and zoning of submarine landslides can guide the site selection and risk prevention of offshore engineering facilities. In this paper, an unsupervised machine learning spectral analysis algorithm was used to evaluate the risk of submarine landslides in the Chengdao sea area of the Yellow River Estuary. A model of submarine landslides risk assessment with 9 input parameters, 4 output parameters and 0.08 as kernel function parameters is constructed. By using this model, the study area can be divided into 4 parts: high, quite high, quite low and low risk of submarine landslide. The comparison between the evaluation results and the distribution characteristics of geological environment factors show that the most important factors are the type of seafloor sediment and hydrodynamic action, and the most important trigger factor is liquefaction. The analysis results of model parameters present that the evaluation results with slightly lower accuracy can be obtained by reasonably simplifying the input factors, and the kernel function parameter is important index affecting the evaluation accuracy. The above research shows that the unsupervised machine learning algorithm can be well used in the risk assessment of submarine landslides, and the richness and accuracy of data categories are important factors affecting the assessment accuracy.

The occurrence of phosphatization will lead to the dilution of major ore-forming elements in polymetallic crusts and thus inhibit the growth of crusts in general. Phosphatization occurred in the Pacific Ocean in an episodic manner, and the occurrence periods correspond to the phosphatization layers in crusts and the geochemical characteristics of P, Ca and other elements, providing evidence for the dating of crusts. However, due to the frequent occurrence of phosphatization in multiple layers of crusts, a more reliable age frame needs to be determined before it can be mutually corroborated with phosphatization events. In this study, the Co-Os dating system with large dating range and the ability to determine hiatus was applicated in dating for the crust samples from central Pacific and western Pacific. With the naked eye identification of phosphatization mineralization features and geochemical profile characteristics, the age frames were proved and the effect of phosphatization on crust mineralization were discussed. The two large-scale phosphatization phases of 39–34 Ma and 27–21 Ma all correspond to the large-scale discontinuous phases of the crusts, while most small-scale phosphatization events in 71 Ma, 55 Ma and 31 Ma can be identified in the layers and geochemical profiles, corresponding to the rising and peak characteristics of P and Ca content. On the one hand, it is confirmed that the occurrence of phosphatization inhibits the growth of crusts, and has a wide range of influence area and a clear time interval in Pacific. On the other hand, it proves the accuracy of the chronological framework of polymetallic crusts.

It is no doubt that there is plenty of “water” (existential form: H₂O, H₂ and (HO)⁻) existing in the mantle which can either exist in the form of fluids and melts or exist in aqueous minerals, nominally anhydrous minerals (NAMs) and dense hydrous Mg-silicates (DHMS). In this paper, “fluid” mainly refers to water which includes elements and compounds that dissolved in or migrated with it. Fluids, mainly consisting of water, play important roles in major geologic processes such as subduction zone earthquakes, mantle partial melting, magmatism and submarine hydrothermal activities. The subduction zone is a key place where the hydrated oceanic lithospheric plate subducts into the earth’s depth. And it is also an important zone of crust-mantle interaction. In the subduction zone, fluids are carried into the deep earth by the subducting lithospheric plate, part of the fluids are released into the overlying mantle wedge by extrusion, frictional heating and metamorphism, thereby lowering the melting point of mantle materials and causing magmatism; on the one hand, the ascending magma heats seawater that penetrates through cracks or rifts; on the other hand, the heated seawater and post-magmatic fluids generated by magma cooling compose the material basis of modern submarine hydrothermal activities; submarine hydrothermal activities not only affect the material composition of ocean water and ecological environment by importing a large number of underground elements or substances into ocean water, but also lead to the formation of hydrothermal polymetallic ore deposits with important economic value. Therefore, the fluid is a medium in the plate subduction process and the various important geological processes caused by it, thus it is a tracer to study these important geological processes. Based on the analysis of the main geological processes of fluids in the oceanic lithosphere subduction, this paper discussed the roles of fluids in earthquake mechanism, magmatic processes, modern submarine hydrothermal activities and subduction zone fluid mineralization. Furthermore, it is suggested that the recent research work should focus on these four aspects: (1) Making the assessment of the fluid flux subducted into the deep earth more accurate to solve global geochemical or material circulation problems. (2) Describing physical and chemical behaviors of fluids in plate subduction comprehensively and accurately, establishing theoretical models of fluid geological processes in subduction zones. (3) Making full use of modern tests and analysis methods, and obtaining accurate data in terms of in-situ analysis of minerals, testing physical and chemical indexes of fluid inclusions in minerals, stable and radioactive isotope analysis, etc., so as to find out the state and process of substances deep underground which can not be reached by current sampling and observation methods. (4) Developing numerical simulation technique to establish theoretical models of geological processes of fluids in subduction zones.

The photosynthetic active radiation (PAR) plays a significant role in regulating ocean primary productivity, so it may indirectly affect the abundance and spatial distribution of cephalopods. In this study, we examined the relationship between photosynthetic active radiation and Ommastrephes bartramii stocks in the Northwest Pacific Ocean, and evaluated the impacts of the anomalous climatic environments on the squid stocks, based on the fishery data during 2006−2015 obtained from the squid-jigging Science and Technology Group of Shanghai Ocean University and the remotely satellite data of PAR. The results indicated that catch per unit effort (CPUE), latitudinal gravity center (LATG), PAR and its spatial distribution exhibited significant monthly variation. From July to November, the suitable range of PAR was 36−39 E/(m²·d) in July, 33−36 E/(m²·d) in August, 24−27 E/(m²·d) in September, 18 E/(m²·d) in October and 12 E/(m²·d) in November. The most favorable PAR was 36 E/(m²·d), 33 E/(m²·d), 27 E/(m²·d), 18 E/(m²·d), 12 E/(m²·d), respectively, from July to November. The results showed that a significant positive relationship (p<0.05) was found between CPUE and PAR, and further a significantly positive correlation (p<0.05) was found between CPUE and the monthly percentages of suitable PAR accounting for the whole fishing ground. Meanwhile, the LATG varied with the mean latitude of the most preferred PAR in each month. Finally, under the anomalous climatic environments, the CPUE in the La Niña years is higher than that in the El Niño years, which may be caused by the higher PAR in the La Niña years. Our findings indicated that the PAR strongly affected the abundance and spatial distribution of O.bartramii in the Northwest Pacific Ocean.

Using fishery data of Scomber japonicus from Chinese light-purse seine fishing on the high seas of the Northwest Pacific Ocean from May to November during 2014 to 2017, and the environmental remote sensing data, the habitat suitability index (HSI) model of Scomber japonicus was constructed based on fish catch and nos of hauls, respectively. Applying sea surface temperature, sea level anomaly, chlorophyll a concentration, the suitability index model of each environmental variable was established by one-dimensional exponential regression fitting. The weight of each environmental factor was determined by linear programming method to improve the prediction precision of HSI model for fishing ground. The prediction accuracy of the HSI model was verified with the actual fishing data from May to November in 2018, and the results showed that in the sea areas with HSI values over 0.7, the fishing catches accounts for 77.29% for HSI model based on fish catch and 76.79% for HSI model based on nos of hauls respectively, which indicates that the HSI model based on different environmental factor weights can better predict the central fishing ground of Scomber japonicus on the high seas of the Northwest Pacific Ocean.

Observations were carried out at Nanliu River, Dafeng River, Qinjiang River, Maoling River and Fangcheng River in the Beibu Gulf to analyze the distribution characteristics and fluxes of nutrient in February (dry season) and August (flood season) 2018. The results showed that significantly variations of nutrient concentration were observed, and the nutrient concentrations in the Fangcheng River, Maoling River and Qinjiang River in the dry season were higher than that in the flood season, while the nutrient concentrations in the Dafeng River and Nanliu River in the flood season were higher than that in the dry season. Nitrate (${\rm {NO}}_3^- $) was the predominant species of dissolved inorganic nitrogen (DIN) during the flood season, while the ${\rm {NH}}_4^+ $ content in the Fangcheng River and Dafeng River increased during the dry season. Based on the runoff data and nutrient concentration, the fluxes of nitrogen and phosphorus into the Beibu Gulf were calculated to be 1014607 tons and 47929 tons respectively in 2018, of which DIN accounted for 77% of total nitrogen and ${\rm {PO}}_4^{3-} $ accounted for 40% of total phosphorus. During the flood river, higher nutrient fluxes were found in the Nanliu River, followed by Dafeng River, Fangcheng River, Maoling River and Qinjiang River. While in the dry season, the flux of nutrients from rivers to the coastal gulf changed significantly due to the influence of regional pollution. Compared with the historical data, the fluxes of nutrient into the coastal gulf increased significantly, which may be responsible for the increase of water eutrophication in the coastal Beibu Gulf. High and different terrestrial inputs transported by the rivers in northern Beibu Gulf may lead to an extensive impact on the ecological system of the Beibu Gulf.

The qualitative and quantitative analyses on betaine lipids of microalgae were conducted by means of the quadrupole flight time ultra-high performance liquid chromatography tandem mass spectrometry (UPLC-Q-TOF-MS) using electron spraying ionization. As a result, 133 betaine lipids including 53 DGCC, 41 DGTS and 39 DGTA were identified from 14 species of microalgae in four major phyla. DGCC was the dominant betaine lipid in dinoflagellates and haptophytes, while DGTS was the main betaine lipid in chlorophytes. There were two main types of betaine lipid in diatoms: DGCC in centric diatom and DGTA in pennate diatom. The differences of fatty acid of betaine lipid in marine microalgae were only observed at the phyla and class levels, but at lower taxonomic levels the differences were less stable. DGCC existed in diatoms, dinoflagellates and chlorophytes, which contained C14−C18 saturated and unsaturated fatty acids and C20 and C22 polyunsaturated fatty acids. The difference in DGCC is that saturated C14−C18 fatty acids existed in dinoflagellates, while the fatty acids of odd carbon numbers C19 occurred only in diatoms. The results of description and molecular characterization of betaine lipid in microalgae can be served in future investigation in chemotaxonomy, physiology, ecological role of microalgae and functional properties of these phosphorous-lacking polar lipids.