Based on the concentrations and spatial distributions of heavy metals in 404 surface sediments from the Bohai Sea, we evaluated the marine sediment environmental quality indexes, such as heavy metal potential ecological risk, geoaccumulation index. Moreover, the factors that impact on the concentrations of heavy metals in surface sediments were also analyzed. The results showed that the mean concentrations of all eight heavy metals were highest in the Bohai Bay, and were lowest in the Bohai Strait. The potential ecological risks of Cd and Hg elements were high and moderate-high, respectively. The assessment of total potential ecological risk revealed Bohai Sea belongs to moderate potential ecological risk. Only few stations of Cr and Ni exceed the upper limit of toxic threshold, and the others are less than the lower limit of toxic threshold. This implies the occurrence probability of toxic pollution is low. The concentrations and spatial distributions of heavy metals were mainly dominated by grain size effect of surface sediments from the Bohai Sea. However, Cd element which was rich in the Jinzhou Bay and Fuzhou Bay of Liaodong Bay was mainly contributed by human activities. Hg element, supplied by Yellow River possible impacted by human activities, was rich in the Yellow River Delta and Laizhou Bay.

According to the data collected from bottom-trawl surveys in Haizhou Bay and adjacent waters during spring and fall in 2011 and 2013–2016, generalized additive model (GAM) based on the Tweedie distribution was used to examine the relationship between the distribution of small yellow croaker (Larimichthys polyactis) and environment factors in different seasons and ontogenetic stages. Combined with the bottom sea water temperature (BSWT), bottom sea water salinity (BSWS), water depth, sediment types, and abundance of prey (Crangon affinis, Leptochela gracilis, Engraulis japonicus, Thrissa kammalensis), the conditional index k and Variance Inflation Factor (VIF) were used to measure the degree of multicollinearity between these factors. The results of multicollinearity indicated that all factors can be used as explanatory variables. The results of Tweedie-GAM show that the factors affecting the distribution of small yellow croaker and their deviance explained varied greatly with seasons (spring and fall) and ontogenetic stages (juvenile and adult). For example, the factors affecting the spring-juvenile small yellow croaker distribution were BSWT, BSWS, water depth and the abundance of C. affinis, which depth had the largest deviance explained (16.09%). In addition, the factors affecting the spring-adultl yellow croaker distribution were BSWT, BSWS, water depth and the abundance of C. affinis and E.japonicus, which BSWS had the largest deviance explained (13.56%). The distribution of small yellow croaker in different seasons and ontogenetic stages was found to be closely related to its ecological habits, environmental factors and distribution of prey in Haizhou Bay and adjacent waters.

Through 70 years of chemical oceanography research, China has entered a period of rapid development in synchronization with the world's advanced level in this field. The remarkable characteristics of marine chemistry study in China are as follows: (1) the study of marine chemistry has shifted from the study of geochemical distribution systems of elements to the study focused on revealing the deep-seated marine biogeochemical processes; (2) the study of chemical oceanography has achieved to become a comprehensive and interdisciplinary study of multi-fields and multi-viewpoints; (3) more attention has been paid to the study of the changes of marine ecological environment under the influence of both human activities and natural changes, and for offshore and coastal zones, more importance has been attached to analyzing the change process from the perspective of the integration of land and sea. In this paper, we summarized and analyzed the important progresses and developments status of marine chemistry research in China in the past 30 years, mainly from the perspectives of the marine biogeochemical processes of biogenic elements, the marine chemistry of trace elements and isotopes and the chemical oceanographic processes under the effect of biological processes. We hope this can provide references and illuminations for the further study of chemical oceanography.

Ocean observation is to observe unknown ocean by acquiring time serial data from the ocean which is the must for ocean science research and attracts more and more interests recently. The paper defines and classifies the ocean observation and discusses how to tell the differences between ocean observing and ocean monitoring. Based on the understanding of ocean observation, ocean observing methodology are discussed in detail, differently in the aspects of observing technology, real-time performance, cost effectiveness and applicability. The author’s research work shows that the better understanding of observing data secures the ocean observation quality; the observing measure especially its platform is critical for the real-time observating performance , which meets the requirement of ocean observation; the cost effectiveness determines the selection of observing methods, and its applicability defines the best form of observation and even creates brand-new kinds of observing technology.

The research progress of macrobenthic biodiversity and ecology from the deep-sea in the world is reviewed in the present paper, especially the advances on the investigations and studies of macrobenthic biodiversity and ecology from the hydrotherms, cold seeps, seamounts, abysses and whale carcasses in China. The prospect of the future researches in China is also discussed.

Since the founding of the People´s Republic of China 70 years ago, China has made great achievements in the field of marine satellite remote sensing technology. China has formulated a long-term plan for the development of autonomous ocean satellites, and has constructed three series of ocean satellites, namely, ocean color, ocean dynamic environment and ocean surveillance and monitoring. A ocean space surveillance network dominated by China´s autonomous satellites has been gradually formed, which includes resources and environment monitoring, disaster prevention and mitigation, and safety management. Rationality and other aspects have played an important role. This paper reviews the development of ocean water color and ocean microwave (marine dynamic environment) satellite remote sensing technology in China, emphatically introduces the new achievements in the field of ocean satellite remote sensing technology in China, and prospects the future development of ocean satellite remote sensing technology in China.

This paper reviews development history and academic achievements of the research of physical oceanography branches in China over past 70 years since foundation of new China. The physical oceanography research in China began with studies of sea waves, tides, offshore circulation, water masses, and ocean meteorologic disasters with emphasis on the storm surge. With the rise of China, the research fields have been gradually expanded. Meanwhile, a great deal of significant research results have been achieved, such as, developed general wind wave spectra and swell spectra that are adapted broadly by the international community as well as the third generation sea wave numerical models; establishment of analytical and forecast methods for tides and tidal currents including quasi-harmonic analytical methods and permanent forecast methods of tides and tidal currents; discovered and named Mindanao Undercurrent, revealed multi-core structures and mechanisms of multi-scale variability of the Kurohsio in the East China Sea, and systematically described the circulation system of the western boundary of the Pacific; proposed the South China Sea Branch of Indonesian Throughflow (the South China Sea Throughflow); gradually improved continental shelf circulation systems of China offshore waters, and obtained deep understandings on the South China Sea circulation, the Kuroshio and its branches, Taiwan Warm Current, Zhejiang-Fujiang Coastal Current, the Yellow Sea Cold Water Mass Circulation, the Yellow Sea Warm Current, the Bohai Sea Circulation and continental shelf trapped waves; systematically summed up inter-ocean interactions of the Pacific Ocean-the Indian Ocean-the Atlantic Ocean through the atmospheric and oceanic bridges; developed methods for the water mass analysis of shallow seas, generally clarified features and mechnisms of distribution and evolution of water masses in China offshore waters, and had contributions to studies of distribution and movement of water masses in deep oceans and polar oceans; clarified general features and generation mechanisms of mesoscale eddies in the South China Sea, explored 3-D structure of eddies, and quatitatively estimated material and energy transportation abilities of eddies in global oceans; basically clarified spatial distribution and seasonal variability features of ocean fronts in China offshore waters, proposed frontogenesis mechnisms including topograpgy, barotropic and baroclinic instabilities; built mooring observation net for internal waves in the South China Sea, achieved systematic understanding of mechnisms for the full process of generation-evolution-dissipation of internal waves; development of shear instability theories of turbulence and ocean turbulence models, proposed a concept of current edge instability and new methods for turbulence-mixing paraterization; obtained new understandings for ocean interior mixing mechanisms and energy sources, and clarified effects of mixing on the deep layer circulation and nutrient material transportation processes; developed the Global Wave-Tide-Current Coupling Model, and a series of ocean and climate models; developped ocean data assimilation systems that may assimilate the majority of ocean observation data and coupling assimilation systems used for ENSO prediction; built physical model experiment platforms with ageostrophic water tanks/pools and geostrophic rotation platforms that satisfy the international standards; developed error analysis methods for ENSO prediction, built theory systems for inter-decadal variability of ocean and climate systems, explored response of mid-deep ocean layers to global climate change; primarily built ocean observation net in China offshore waters; continued Arctic and Antarctic expeditions; built operational forecast systems for typhoon, storm surge, extremely high waves and tsunami to provide supports for reducing meteorologic disasters in China; broke through foreign blockade to ocean technologies, successfully developed 10 km deepwater hydrophone and a series of instruments for observing ocean optical features; developed prediction models for oil spilling and dangerous/chemical material drifting and spreading in order to provide scientific supports to emergence processes and warning/forecast of risk events that are brought along ocean resources development. A great deal of literatures of academic results cited in this paper (maximum 3 papers selected for each first author) show that the development of physical oceanography research over past 70 years has trained a research team with solid strength. This is the most precious achievement. This research team will serve as a principal force to scale new heights in physical oceanography in China.

The South China Sea (SCS) is the largest marginal sea in the Western Pacific Ocean. Major advances in understanding SCS tectonic processes have been made in the last several decades, especially through the implementation of five international ocean drilling expeditions during 1999-2018 and the “South China Sea Deep” major research program of the National Natural Science Foundation of China (2011-2019). Critical data have been acquired and important scientific results have been obtained, which have changed our view of how the SCS marginal sea basin developed and evolved. Major progresses have been made in multiple aspects: (1) the SCS is proposed as a new type of “plate-edge rifting” model, which differs from the classic Atlantic-type “intra-plate rifting” model; (2) Ocean drilling obtained the SCS basement basalt samples for the first time, which together with the first deep-towed magnetic survey, enabled the determination of SCS basin ages and revealing that the SCS seafloor spreading propagated stepwise from east to west; (3) Magmatism appeared rapidly during thinning of lithosphere in the SCS northern margin, in sharp contrast to serpentinite exposure by relatively slow rifting of the Atlantic Ocean; (4) Magmatic activity is still significant after the cessation of SCS seafloor spreading, being controlled by multiple tectonic and mantle processes; (5) Geochemical evidence and geodynamic simulations show that the SCS magmatism is affected by the surrounding subduction zones. At present, marine geoscience research of the SCS is being extended to studies of its interaction with surrounding ocean basins. Through conducting large-scale research programs, building ocean drilling platform, and strengthening international collaboration, China’s contributions to marine geoscience research are expected to increase.

Offshore eastern Taiwan situated in the West Pacific active zone, there are multiple hydrothermal vents among which Kueishantao (KST) and Lutao (LT) host the most active systems. This paper reviewed the progress of the geochemical characteristics and biological responses of the KST and LT hydrothermal systems. The vent fluids emanated from the shallow KST hydrothermal vents have the world's lowest pH (1.52) values of any submarine vents. The fluids are rich in heavy metals and are accompanied by gases composed mostly by CO₂. The hydrothermal vents are considered to be a source for chromophoric and fluorescent dissolved organic matter in the oceans. The hydrothermal systems showed the world’s lowest concentration of dissolved organic carbon (14 μmol/L) and unique kinetic characteristics in Lutao. Native sulfur chimneys and sulfur balls were found around the KST vents. The highly toxic and acidic KST vent fluids have disturbed the behavior of ambient macro-organisms including crabs which have developed detoxication measures. The active bacteria groups in the KST field are dominated by Gammaproteobacteria and Epsilonbacteraeota that are involved in the carbon, sulfur, and nitrogen metabolic pathways. Sulfur-reducing and sulfide-oxidizing chemolithoautotrophs account for most of the primary biomass synthesis, which fuels microbial energy flow and element cycling in the hydrothermal systems. Vent crab evolved an adaptive modulation of reproductive behavior to survive in the hydrothermal vent field. Under the stress of the KST hydrothermal activity, the microorganisms have generated cryptic compounds and metabolic products. Furthermore, both the KST and LD hydrothermal systems are affected by tides and catastrophic events such as typhoons and earthquakes. The studies on the hydrothermal systems at offshore Taiwan are of essential importance for investigating the geochemical cycles and eco-environmental impacts of global hydrothermal systems.

The typhoon intensity-frequency relationship over a long period of time is related to climate change, but it is difficult to provide sufficient information from instrumental and historical records. Therefore, to extract storm information from sedimentary records has become a critical scientific problem; the solution to the problem can provide a decision-making basis for coastal cities to cope with future climate and sea level changes. The present study on the progress in the research of typhoon sedimentary records shows that shelf mud deposits, beaches and coastal dunes, tidal flats, lagoons and storm boulders contain records of extreme events. These event layers can be identified by stratigraphic sequence features and sediment characteristics. Typhoon records along the coastline of China have been found in large quantities, but further improvements to the information-obtaining methodology are needed to distinguish between deposits of typhoons, winter outbreaks, river floods and tsunami events. Thus, in terms of the information on typhoon intensity in shelf muds, coarse-grained and shell particles in the deposits can be used as indicators of intensity of bottom resuspension, but calibration with sufficient measurements is required. The elevation of typhoon deposit on the top of beaches and coastal dunes may indicate the height of swash during a typhoon event, while the size of storm boulders has a significant correlation with the offshore wave height. These data can be used to deduce typhoon intensity, although they are not enough to establish the intensity-frequency relationship. Tidal flat and lagoon deposits have a high continuity and can be used to reconstruct the time series of typhoon events. However, the solution to typhoon intensity is not unique because different combinations of maximum wind speed, path, landing place and duration may produce the same event deposit. We propose that a new method of obtaining typhoon information should be developed to solve this problem. Numerical simulation of modern process, with the help and assimilation of available data and knowledge of typhoon events, would be useful to reproduce the characteristics of event deposits. Then, inverse simulation for event deposits can be carried out for multiple locations, to constrain the solution domain. This method may be referred to as "solution domain constraining method". The uncertainty can be further reduced by means of big data analysis, i.e., incorporating other dataset of typhoon intensity into the simulation system. A combination of dynamic process simulation and big data treatment is helpful to the establishment of the intensity-frequency curve of typhoon with the same time scale as the sedimentary record; on such a basis, the relationship between typhoon variation and climate change can be analyzed.