Ommastrephes bartramii is an economically important species for Chinese squid jigging fleet. Understanding the spatio-temporal distribution on fishing ground is crucial to the sustainable utilization of fish resources. The study constructed BP (back propagation) neural network models with different scenarios to speculate the dynamics of O. bartramii abundance based on fishery data in the months of July to October during 2000 to 2015. The model with year, month, longitude, latitude, sea surface temperature (SST), and sea surface salinity (SSS) as independent variables, 8 neurons in hidden layers, had the smallest mean square error, and thus selected as optimal model. The results showed that the significant fluctuation in CPUE between years, the local abundance was low and scattered in July and October, whereas was high and concentrated at 41.5°−43.5°N, 155°−160°E in August and September. Environmental factors, including SST and SSS affect the spatio-temporal distribution of local abundance, and should be considered in stock assessment and management.

Funded by the National Key Basic Research Development Program, a multi-vessel oceanography survey was conducted synoptically in the South China Sea (SCS) in August 2000, which appeared to be the unique, available synoptic survey that covered the entire SCS basin in deep summer. A number of difficulties were encountered during the survey that affected the quality of observation, even though they were resolved underway. Although some related research works were previously published, no carefully quality control of the data and a comprehensive analyses had ever appeared before. In this work, the original CTD and shipboard ADCP data were carefully calibrated in the first place, and the hydrography and circulation features were then analyzed and discussed to leave a record of the cruises as complete as possible. The results indicate that, in deep summer, the basin shows different physical characteristics on both sides of its SW–NE oriented axis of the basin. The circulation is generally anticyclonic southeast of the axis, in which the Nansha anticyclonic gyre (NSAG) is especially powerful; the area northwest of the axis, in contrast, appears to be dominated by mesoscale features of different categories, where no obvious structure of large scale circulation is found. The analyses confirm that the scales of the NSAG are over 400 km horizontally and nearly 1000 m vertically, with a maximal swirling speed close to 1 m/s, which appears to be the most remarkable circulation feature of the SCS. Moreover, its position and strength are subject to significant interannual variation. In the Mindoro Strait, the exchange flow showes a sandwich structure during the observation period. This is different from our previous understanding and suggests that the strait exchange may have different modes varying with the forcing condition.

Trophic level among main organisms in costal water of Lüsi fishing ground in summer, 2018, were analyzed in this study by stable isotope method. Using IsoSource model, we calculated potential carbon source contribution of the phytoplankton, POM and SOM of consumers, and then compared the former and latter TLs variation of main organisms by overlapping potential carbon source influence. Results showed that phytoplankton and SOM were main potential carbon source of main organisms in costal water of Lüsi fishing ground in summer. Two trophic level spectrums were constructed by overlapping three potential carbon sources and a single species as the baseline organisms, respectively. The trophic level of the right trophic level spectrum ranged from 1.74 to 3.92, which was averagely 0.19 lower than that of the left trophic level spectrum. Although the overall trend was unchanged, the trophic positions of some fish and most shrimps were changed in two spectrums. The baseline organisms in the right trophic level spectrum changed with the different stacking ratio of potential carbon sources, which could reflect the trophic level more effectively and was more suitable for organisms at low trophic levels, such as shrimp and crabs. However, this had little impact on fish in the position of middle and advanced consumers.

The instabilities of longshore currents are the far infragravity band waves. The study of its propagation characteristics will help us to understand its influence on the evolution of coastal beach and the transport and migration of pollutants, fish eggs and other organisms. Based on the wavelet coherence spectrum, this paper analyzes the propagation characteristics of the unsteady motion under regular and random waves, and discusses the influence of the wave height, period and slope on it. The results show that the irregular wave is easier to induce the unsteady motion, and the positive or negative phase difference of the unsteady motion is about 30° in the case of irregular waves, which is similar to the incident angle of waves; with the increase of the incident wave height, nonlinear effects become stronger and the period range of the unsteady motion will be wider, that is to say, it is easier to induce the unsteady motion; the incident wave period has a little effect on the propagation; the steeper the slope is, the more likely it is to induce the instabilities of longshore currents.

The asymmetry of flood and ebb plays an important role in the process of sediment transport and geomorphological evolution, which is a significant feature of the flow field in estuaries. The erosion and accumulation, sediment transport and sediment characteristics in the Huanghe River Estuary based on the measured topography, sediment particle size, hydrological and sediment observation data were analyzed in this paper. The Delft 3D model was used to simulate the flow field in the Huanghe River Estuary, and the spatial distribution of magnitude differences between flood and ebb velocities under different conditions were calculated. Combining the above, the dynamic mechanism of erosion and accretion in coastal area of the Huanghe River Estuary was discussed. The results show that there are multiple siltation and erosion centers distributed between the active river mouth and the Laizhou Bay. There is a noticeable asymmetry of flood and ebb velocities in the area, and there is the flood dominant area off the active river mouth, extending the Laizhou Bay southward in a tongue shape, while the near shore and the Laizhou Bay are dominated by ebb. The erosion and deposition in the Huanghe River Estuary are largely controlled by the spatial distribution of flow velocity asymmetry and the conversion of dominant flow. The strong north wind strengthens and expands flood-dominance, and promotes siltation and coarsening of sediment in the Laizhou Bay.

Online monitoring of pollutants exporting into coastal waters is one of the key technique to realize marine pollution control and coordination of monitoring and management. In this study, based on salinity and fluorescence dissolved organic matter (FDOM) sensor data between 2014−2018 from a multi-parameter buoy deployed in Jiulong River Estuary, a rapid inversion model of chemical oxygen demand (COD) was established. Daily river end member COD concentrations were then extrapolated by effective concentration method. Combined with daily runoff data, daily estuarine export fluxes of COD between 2014 and 2017 were estimated. The factors controlling the flux variations were quantified by flux decomposition model. The results indicated: (1) The average concentration deviation of the inversion was (10.4±8.8)%, indicating the good reliability and stability of inversion model. (2) On seasonal scale, COD concentration in dry season of 2016 was lower than the other dry seasons, which was regulated by 2015−2016 super El Niño events. However, the sharp increase of runoff still significantly increased the COD export flux. (3) On annual scale, the COD export flux in 2016 from the Jiulong River 4.4 ×10⁴ t/a was significantly higher than the other three years (3.0−3.2)×10⁴ t/a. The abnormal precipitation in 2016 caused by 2015−2016 El Niño event was the major reason for such yearly variation. This study highlighted the application of online FDOM sensor system for high frequency monitoring of COD export. This would help to achieve long-term continuous high-frequency monitoring of land-based pollutants and their fluxes into the sea and their regulatory factors. This would provide important technical support for marine ecological environmental protection and management.

Samples of Jumbo flying squid (Dosidicus gigas) were collected from Chinese squid jigging vessels in the high seas of Ecuador, Peru and Chile in the southeast Pacific Ocean in 2015 and 2017. The trace elements in the eye lenses of D. gigas were measured to study the geographical differences and their relationship with sea surface temperature. The results showed that elements such as Mg²⁵, Ni⁶⁰, Cu⁶³, Sr⁸⁸ and Ba¹³⁷ in the peripheral part of eye lenses of D. gigas in the high seas of Ecuador, Peru and Chile were significant difference, while there were no significant differences between each two sea areas in the elements of Na²³, Al²⁷, Si²⁹, P³¹, Ca⁴³, Mn⁵⁵, Zn⁶⁶ and Pb. Except for Sr⁸⁸, Ba¹³⁷, Fe⁵⁷ and Ni⁶⁰, which showed significantly linear negative correlations with SST (p<0.05), there were no significant correlations with SST in the other elements (p>0.05). Sr⁸⁸, Ba¹³⁷, Fe⁵⁷ and Ni⁶⁰ could be regarded as indicator elements of the ambient temperature of D. gigas, and Ba¹³⁷ could also be regarded as indicator element of the water depth and upwelling. Consequently, trace elements in eye lenses could be used to reconstruct the habitat environment of cephalopod.

After the launch of China’s HY-2B altimeter in October 2018, NSOAS (National Satellite Ocean Application Service) conducted a HY-2B altimetry calibration experiment in Wanshan, Zhuhai. The experiment used the tide gauge along the coast to conduct the calibration experiment from November 3, 2018 to December 12, 2018, near the sub-satellite point of the HY-2B transit orbit 375 on Zhiwan Island. During the experiment period, HY-2B revisited the calibration point three times, and the results showed that the three-period HY-2B altimetry calibration bias were (3.06±3.48) cm, (2.85±1.03) cm, −7.41 cm; there was a certain drift in the calibration bias in the first three cycles, and subsequent calibration work was required to determine the cause of the drift.

The critical point is an important component in the topological structure of the ocean flow field. Feature extraction based on the critical point is of great significance to reveal the topological characteristics of the ocean flow field and carry out the topological analysis of the ocean flow field. In this paper, based on critical point theory and Sperner lemma, the improved bilinear interpolation algorithm and Sperner complete labeling method were integrated to extract the critical point features of ocean flow field data. First of all, we added sliding window to the bilinear interpolation algorithm to filter the candidate grid cells of the critical points, and use the aggregation idea to solve the ambiguity problem of grid interpolation by reducing the grid resolution. At the same time, we considered nine cases of the zero value grid, and used the iterative aggregation idea to slide filter the candidate grid cell, which solves the case that the interpolation grids are all 0. Secondly, the extraction rule of critical points of minimum method based on Sperner complete labeling was proposed, and the grid center with the smallest velocity vector module is taken as the critical point to solve the non-zero critical point extraction in the actual flow field physical scene. By combining and de duplicating the two extraction results, more comprehensive critical point extraction and classification results can be obtained. Finally, through the analysis of the experimental results of the flow field data in multiple sea areas and different depths, the effectiveness and feasibility of the integrated critical point extraction algorithm was proved.

Based on the on-site observation of the topography, a generalized three-dimensional physical model of coral reef-lagoon-channel system was established in the wave basin. Wave gauges, velocity meters, and surface velocity measurement system were used to analyze wave and current field characteristics at different locations under regular wave condition. The experimental results indicate that over the reef flat, the wave height gradually decreases by 86.7% cross-shore, and wave-induced setup first increases and then decreases by 65.9% along the reef. The mean current direction is mainly cross-shore, and there is a tendency of increasing first and then decreasing. In the lagoon, the wave height is larger near the channel, where wave-induced setup is the smallest. The maximum wave height is about 2.8 times of the minimum value, and the wave-induced setup is 25.5% lower than on both sides. The mean current is mainly a longshore one that points symmetrically to the rip channel. The velocity increases from the two sides to the rip channel first and then decreases. The wave height in the channel does not change much, and largest wave-induced setup is 47.6% than that on the reef. The mean current flows offshore, and increases first and then decreases. Using the results measured by the wave gauges, the spatial changes of the radiative stress and wave surface pressure gradient which drove the circulation were quantitatively analyzed. The current change on the reefs is the result of the interaction between wave surface pressure gradient and the radiant stress. The driving force of the offshore flow in the rip channel is mainly the radiant stress, while the change of the longshore current in the lagoon is determined by the pressure gradient of the mean water level.