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.

As a kind of coastal accumulation body in high-energy environment, natural gravel beach is a good coastal protection barrier due to its coarse particle size and large porosity. The gravel morphology is an important parameter to understand the gravel formation process, but it is difficult to obtain the quantitative parameters of a large number of gravels quickly and accurately. In this study, we surveyed three gravel beaches (Jiuzhangya, Yueyawan, Changtan) in the Beichangshan Island, four gravel beaches (Xianjingyuan, Linhai, Changshanwei and Mingzhuguangchang) in the Nanchangshan Island in the Shandong Province. We measured beach profile, collected gravel samples and took gravel images. Using the software ImageJ for digital image measurement in situ without interference, we can quickly obtain a large number of gravel morphologic parameters, including particle size, grinding roundness and shape ratio. The results show that the range of the particle size is 4−79 mm, which was mainly pebbles. The average particle size of the beach in the Beichangshan Island is slightly smaller than that in the Nanchangshan Island, with the largest average particle size of gravels in the Jiuzhangya Beach of the Beichangshan Island and the smallest one in the Xianjingyuan Beach of the Nanchangshan Island. From beach berm to the high tidal line, the average particle size decreases gradually, but increases at waterline. The range of roundness of gravel is 0.59–0.75, and the grade is round. The gravel beaches have reached a relatively mature stage based on roundness, with the best roundness in the Yueyawan Beach and the worst roundness in the Changtan Beach of the Beichangshan Island. The gravel roundness increases from land to sea. The shape ratio ranges from 1.36 to 1.77, which is negatively correlated with the gravel roundness (R²=0.98). The gravel gradually changed from long strip to elliptic shape from land to sea. The gravel beaches morphology of the Changshan Island is affected by the provenances, dynamic conditions and human activities. The slope range of the gravel beach in the study area is 16%−35%, and they are positively correlated with the gravel particle size.

It is a common ocean phenomenon that eddies attract each other and propagate in the form of dipole mode, and these dipoles play an important role in transporting seawater, nutrients and other substances. In this paper, a global dipole pair automatic recognition method based on the eddy trajectory data is proposed. By using the K–D tree for cutting space, the eddy trajectory data are calculated from January 1993 to September 2016, and a total of 86 662 westward moving dipoles and 30 590 eastward moving dipoles with a life cycle of more than 60 days are found. The global characteristics of the dipole that we detected are analyzed, and the reliability of the automatic recognition algorithm is verified by the comparison and test with sea surface temperature anomaly and sea surface salinity anomaly. Finally in this paper, the transmission modes and characteristics of dipoles are analyzed, including the characteristics of long life, high propagation speed and entanglement trajectory.

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 diffuse attenuation coefficient (K_d) is an important marine optical parameter, which can provide the basic data for the water environment change, the water quality analysis and the aquaculture. There are some limitations of the traditional methods, such as the low efficiency and resolution of the traditional shipborne field measurement and the rough inversion accuracy and spatial resolution of the satellite remote sensing. Therefore, an extraction method for diffuse attenuation coefficient based on airborne LiDAR bathymetric water column waveform is proposed in this paper. Firstly, the water column contribution is decomposed by the waveform decomposition algorithm for airborne LiDAR bathymetry based on the layered heterogeneous model. Then, according to the attenuation characteristics of laser in water, the diffuse attenuation coefficient extraction model is constructed. Finally, the diffuse attenuation coefficient spatial distribution in a large area of water is obtained. The performance of the proposed method was verified by the measured data from the Ganquan Island in the Xisha Archipelago and the Lianyungang’s seacoast. The experimental results demonstrated that the proposed method could obtain the diffuse attenuation coefficient without the water bottom contribution intensity and depth information for each bathymetric point. And the good results were also achieved in turbid waters. Meanwhile, the proposed method showed the feasibility of employing the ALB system to obtain the high-precision diffuse attenuation coefficient in China coastal waters.

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.

The spatial distribution of Cu, Cr, Cd, Pb, Ni and Co in the Jiaozhou Bay seawater and their distribution among different size fractions were investigated. The distribution mechanism of trace metals and the influence of environmental factors such as plankton activity and salinity during the distribution process were also discussed. The results showed that the highest values for most trace metals were distributed along north and northeast coast, while Cd and Pb also presented high value areas in the mouth and middle of the bay respectively. The trace metals in the Jiaozhou Bay seawater were mostly partitioned in the <1 kDa fraction with an average value of 70.1%, of which the percentages of Cu and Cd were up to 79.0% and 77.6% respectively, while Pb was only 58.2%. Similarly, the bulk dissolved organic carbon was also mostly partitioned in the <1 kDa size fraction with an average value of 73.1%. Spectroscopic properties indicated that low molecular weight (LMW, <1 kDa) fractions which mainly composed of humic-like organic matters contained more effective functional groups like hydroxyl and carboxyl groups and had higher complexing capacities with trace metals. There were significant positive correlations between chlorophyll a concentrations and high molecular weight (HMW, >1 kDa) proportions, indicating that primary production by phytoplankton in the euphotic zone was the major source of HMW dissolved organic matters in seawater and influenced complexation between trace metals and dissolved organic matters. The top area of the Jiaozhou Bay with lower salinity was characterized with higher proportions of large size components, which may be resulted from the combined effects of biological activity, terrestrial input and salinity.

Neon flying squid Ommastrephes bartramii is a cephalopod species of economically importance distributed in the North Pacific Ocean. Because of short lifespan, their abundances mainly depend on the recruitments and the marine environment during their early life stages will directly affect the recruitments. Using fishery data collected by Chinese squid-jigging fleets in the Northwest Pacific Ocean from 2004 to 2015 and the sea surface temperature (SST) of spawning and feeding grounds, which were divided into different numbers of subareas, correlation analysis and random forest model were used to screen out the subareas that CPUE has significant relationships with Ps (the proportion of favorable-SST in spawning grounds) of spawning grounds and Pf (the proportion of favorable-SST in feeding grounds) of feeding grounds during spawning and feeding periods. The Ps and Pf were used as input variables of the neural network model to forecast recruitments based on spawning ground and feeding ground, respectively, and the advantages and disadvantages of the model and forecast accuracy were analyzed. The results show that the schemes of dividing spawning ground into 5°×5° and feeding field into 2.5°(longitude)×4°(latitude) were optimal. The ranges of subareas selected by random forests are largely consistent with those selected by correlation analysis, both random forests and correlation analysis can identify potential subareas associated with CPUE, and both have forecasting accuracy of >90%. However, the subareas selected by the random forest are better and the forecast accuracy is higher than those selected by correlation analysis. In addition, the model based on the spawning ground is more accurate and stable than that based on feeding ground.

In this paper, the time series analysis model ARIMA (1, 2, 0) was applied to simulate and predict the stock of small yellow croaker (Larimichthys polyactis) based on the monitoring catches data of canvas stow net in the southern Yellow Sea from 2003 to 2014 and verified by the monitoring catches data of 2015 and 2016. The results showed that the simulated and actual values for the catch yield from 2003 to 2014 were correlated significantly (p<0.05) and the correlation coefficient was 0.881. The relative error between predicted and actual value in 2015 and 2016 were respectively 6.73% and 22.75%, the overall relative error was 14.74% and the regression equation fitted the real situation better, which illustrated that the time series analysis model ARIMA (1, 2, 0) can be applied to simulate the catches trend of L. polyactis and predict the catch stock, especially superior in short-term forecasting. However, in any case the fixed model of L. polyactis is not always suitable for all data analysis, and the values of p, d and q in ARIMA model are considered to be variable according to different time series. Therefore, the optimal values of p, d and q should be determined based on the guidance and analysis of relevant theories in order to avoid copying directly the fixed model.

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.