Dinoflagellate cysts, as micro-fossil, could be used to trace environmental change history, such as water eutrophication and climate change. But there is controversy on how to indicate water eutrophication, and also it is a problem how to differ the signals between water eutrophication and climate change in dinoflagellate cysts. In order to address these problems, we collected four sediment cores in the Changjiang River Estuary and analyzed their dinoflagellate cysts. Results showed that eutrophication could lead to the increase of total dinoflagellate cysts and Paralytic Shellfish Poisoning (PSP) productive dinoflagellate cysts abundance. And the ratio of hetero/autotrophic dinoflagellate cysts decreased, which implied that the eutrophication mainly resulted from agriculture and domestic sewage in the Changjiang River Estuary. Because of water plume, the eutrophication signal was relatively weak near estuary, strong in middle distance and almost none in far distance. Seasonal change of dinoflagellate cysts was observed in the high sediment sinking area in the estuary, with the lowest production in winter as a result of low temperature. ENSO events will lead to the peak and valley value of dinoflagellate cysts abundance by affecting nutrient input which is transferred by river downloading. Moreover, the signal also varied with the distance: valley and peak value of dinoflagellate cysts present because of strong and weak river runoff pulse near estuary, peak and valley value of dinoflagellate cysts and runoff overlapped and were clear in middle distance, and peak value of dinoflagellate cysts was obvious in far distance but the domain reason was complex. These findings are of great significance to environment history reconstruction, study of red tide history and ENSO events.

In order to study the effect of hypoxia stress on serum of biochemical and non-specific immune indexes of the juvenile cobia(Rachycentron canadum), the fish with body weight of (50.44±2.78) g were treated at dissolved oxygen content of (3.15±0.21) mg/L for 4 weeks. The samples were taken on 1 d, 7 d, 14 d and 28 d respectively for determination of relevant indexes and results showed that: (1) the growth of juvenile cobia was inhibited by hypoxia, the weight gain rate and specific growth rate were significantly lower than the control level (p<0.05); (2) the indexes of liver function showed that activities of aspartate aminotransferase and alanine aminotransferase significantly increased (p<0.01) on 7 d, 14 d, 28 d and 14 d, 28 d respectively, while the content of total protein and albumin significantly increased (p<0.05) on 14 d and 28 d than that of the control group; (3) the content of blood glucose significantly increased (p<0.05) on 1 d, 14 d and 28 d, while the triglyceride significantly increased (p<0.01) on 14 d and 28 d. The total cholesterol content significantly decreased (p<0.05) on 1 d, then continue to increase; (4) the serum ion content changed with different trend, in which sodium ion and chloride ion significantly increased (p<0.01) on 14 d and 28 d. Potassium content increased continuously and was significantly higher (p<0.05) on 7 d, 14 d and 28 d than control level, while calcium content continued to decrease and there was a significant difference (p<0.05) on 14 d and 28 d; (5) activitie of superoxide dismutase and content of malondialdehyde continued to increase and were significantly higher (p<0.01) than those in the control group on 7 d, 14 d, 28 d and 14 d, 28 d respectively. Activities of catalase showed significantly “decreased-increased-decreased” patterns. Activitie of lysozyme significantly increased (p<0.05) on 1 d and then continued to decrease. These results showed that hypoxia stress caused oxidative damage to the juvenile cobia, inhibited its growth and led to significant change in serum biochemical and non-specific immune indexes, which indicating that the nutrient utilization and immune system of cobia were affected.

Based on the hybrid detection method for ocean mesoscale eddy, this paper uses the measured data to verify the detected boundary and center of eddy, and draws the following conclusions. (1) By diagnosing the angle between the detected boundary and the measured current vector, the results show that the detected boundary of eddy can basically reflect the current state of the actual eddy. (2) The center of detected eddy is compareed with the center that inversed by the measured current and temperature data. The results show that the detected center of eddy is basically consistent with the inversed center. Furthermore, by comparing the fitting effect of circle and ellipse to the detected boundary of eddy, the results show that the fitting accuracy of ellipse is higher than that of circle.

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.

A submarine mooring system was deployed in the east of the Luzon Strait and the vertical distribution of high frequency (mostly tidal) variations of ocean currents were analyzed in the paper. Several features were revealed that the tidal kinetic energy of the middle (1 550 m) and the deep layers（2 560 m） was one to two orders smaller than that of the subsurface layers (100−160 m) , and slightly smaller than that of the near-bottom layers (4 040 m); the tidal currents were irregular semi-diurnal in the subsurface layers and were irregular diurnal in the middle and deep layers; the tidal kinetic energy was larger in summer (June to September) and winter (February to March) , which mainly caused by enhancement of M₂ and K₁ tidal components in corresponding periods; the high frequency fluctuations in all layers were mainly in clockwise rotation; the near-inertial frequency in the upper layers (middle and deep layers) were close to (slightly smaller than) the local inertial frequency.

Based on the WRF (Weather Research and Forecasting Model) and its three-dimensional variational data assimilation system, the numerical simulation and Doppler radar data assimilation are conducted with the data of GFS (Global Forecasting System) and JMA (Japan Meteorological Agency) reanalyses as the initial conditions respectively. The impact of assimilation radar data in different background fields on the initial typhoon field, internal structure and forecast were investigated based on the super typhoon case Saomai in 2006. The results show that, both experiments with GFS and JMA data are able to enhance the typhoon initial winds field at 700 hPa and geopotential height field at 500 hPa after assimilating radar observations. The improvements in terms of the root-mean-square error during the 3 h during the data assimilation cycling, the minimum sea level pressure, and the thermal and dynamic structure from the JMA tests are more significant than that with GFS data. The forecast skills for the precipitation, the typhoon track, and the intensity are also noticeable with JMA data by correctly predicting the precipitation location in the front of typhoon.

In the present study, the connection between the Arctic Oscillation (AO) in May and the following summer (June to September) western North Pacific tropical cyclone genesis frequency is investigated based on NCEP/NCAR reanalysis data and tropical cyclone data from China Meteorological Administration for the period 1950–2018. A statistically significant positive correlation is found between the late spring AO and summer tropical cyclone genesis frequency. The diagnosis results show that the low-level relative vorticity, high-level divergence, vertical wind shear and the mid-low level relative humidity are all beneficial for the genesis of the western North Pacific tropical cyclones during the positive AO years. Moreover, the western Pacific subtropical high shifts eastward and northward and tends to be much weaker. On the contrary, during the negative AO years, the tropical cyclone formation is reduced because of the strengthened western Pacific subtropical high combined with an anticyclonic vorticity in the lower troposphere. The possible mechanism involved the variations of the storm track in the North Pacific. It is showed that during the positive (negative) AO years the storm track is moving northward (southward) and there is a cyclonic (an anticyclonic) vorticity anomaly in the lower troposphere in the western North Pacific in the subsequent summer through the interaction between the synoptic-scale eddies and low-frequency mean flow. The resulting anomalous local Hadley circulation could lead to the change of the western Pacific subtropical high and further contribute to the western North Pacific tropical cyclogenesis.

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.

The modern Zhujiang River Delta has experienced the formation and evolution from drowned valley to delta, which is rich in regional characteristics. The research on the Zhujiang River Delta in the past hundred years is summarized into four paradigms: historical description, field investigation-scientific reasoning, instrument applied-discipline theory and “dynamic-sedimentary-morphologic” scale-crossing paradigm. Each illustrated by superb examples and documented. Based on the research of the authors and his team, this paper puts forward several propositions concerning the formation and evolution of the Zhujiang River Delta, which are substantially different from the existing literature, and makes necessary differentiation and analysis from multiple perspectives, including the millennial-scale changes of coastline since the transgression maximum, the mode of formation and evolution of the modern Zhujiang River Delta and the development and its mechanism of the major channels of the network in the delta. Finally, the approache of interdisciplinary, scale-crossing and time-space quantification concerning delta research are briefly discussed.