As China’s first operational ocean color sensor, the coastal zone imager (CZI) carried by Haiyang-1C (HY-1C) satellite is playing an increasingly significant role in offshore ocean environmental monitoring. After the launch of HY-1D satellite, the combination of CZI sensors can provide two observations in three days for coastal zone through dual-satellite system. CZI sensors have demonstrated prominent application advantages for monitoring marine floating algae, oil spill and so on. Since the high spatial resolution optical data contains abundant information about the marine environment, it also brings some distraction to the identification and extraction of specific ocean targets. In this work, a novel CZI algorithm was developed based on cooperation of scaled algae index (SAI) and virtual baseline floating macroalgae height (VB-FAH) to extract floating green tide information in the Yellow Sea from HY-1C satellite CZI measurements. VB-FAH method can be used to enhance the difference between floating algae and sea water, especially for satellite’s sensors with no short-wave infrared bands. After that, the algorithm efficiently rejects the complex interference information in the ocean high spatial resolution optical data by SAI sliding window. The algorithm has high accuracy and time efficiency in the extraction of floating green tide from CZI measurements. Moreover, the study carried out an uncertainty analysis for the area of algae-containing pixels between HY-1C satellite CZI data with 50 m spatial resolution and GF-1 satellite WFV1 data with 16 m spatial resolution. The result indicates that the uncertainty in the inversion results of CZI data mainly comes from the over estimation of small patches of floating algae. The study also pointed out that the uncertainty of optical data for floating algae monitoring is not only from the difference of spatial resolution between two sensors, but also related to the spatial variability of the morphological size of floating algae. Exploring the morphological spatial variability of floating algae will help improve the accuracy of optical data inversion results and clarify the uncertainty.

Hollow blocks have good water blocking and siltation promotion functions, and have been widely used in ecological restoration projects in recent years. In this paper, combined with flume experiment and Flow-3D numerical simulation, the water blocking effect and sedimentation characteristics of open and semi-closed hollow blocks are analyzed. The results show that the permeability of the hollow block plays a leading role in the internal flow velocity and turbulence intensity, and the semi-open hollow block with small permeability has a better effect in slowing down and turbulence control. The suspended sediment concentration near the bottom of open and semi-closed hollow blocks increases by 56% and 75%, respectively. Both of them can promote the deposition of sediment in the block. The environment of low flow velocity, sediment micro-deposition and water and sediment connected inside and outside by hollow blocks is the habitat requirement of macrobenthos, the structure of low turbulent flow inside the semi-enclosed hollow block is more favorable for the habitat and reproduction of macrobenthos.

Based on the long-term observation obtained from two sets of submarine mooring system deployed at Niulang Seamount in the western Pacific, the vertical distribution of the deep currents and the temporal variation characteristics were analyzed in the paper. The results show that: (1) The annual mean ocean currents and the variations were the largest in the upper layer, the second in the middle and deep layers, and the smallest in the middle-deep layers. (2) The subtropical countercurrent was at the depth shallower than 150 m, and the northward current was at depth deeper than 150 m and at the middle layers; the near bottom current was weak southward at the summit of the seamount, but southwestward at the bottom of the seamount. (3) Both at the summit and bottom of the seamount, the currents showed a seasonal oscillation with the most energetic oscillation at a period of about 100 d throughout the water column; at depth above 2 000 m, currents showed a synchronous oscillation in the throughout the water column, with the oscillation amplitude decreasing with depth; current oscillation at deep layers (below 2 000 m) were in opposite phase with that at the upper layers, and the oscillation amplitude was the strongest at 4 000 m.

In this paper, MIKE3 is used to establish a three-dimensional hydrodynamic model of Zhoushan and Ningbo. Based on the tidal current verification with the measured data, the difference between the three-dimensional model and the two-dimensional model is compared. Also, the influence of the change of the tidal current field around the Zhoushan Green Petrochemical Phase III reclamation project before and after the implementation is mainly predicted and analyzed. The results show that: (1) Under the same initial conditions, the tidal level and tidal current validation results of two-dimensional model and three-dimensional model are good, and the two-dimensional results are closer to the measured values in some cases. (2) The three-dimensional vertical velocity distribution shows a decreasing trend with the increase of water depth. In general, the tidal current fitting is good, and the relative error of velocity below 0.6H water depth is between 10% and 15%. Considering that the model may not consider the influence of wind field and wave, the calculated surface velocity of local stations is slightly larger than the measured value; the vertical distribution of flow direction is nearly consistent. (3) Before and after the reclamation project, there was no obvious influence on the tidal current field around the project. Only in the northeast, southeast and northwest corner of Dayushan Island, affected by the “bend improvement” and the channel closure between small islands, there is a change in the local tidal current form. On the whole, the layout of reclamation projects conforming to the shoreline will have an effect on the local coastal tidal current, and almost no effect on the large scale tidal current field in the far sea.

As one of the most important water quality parameters, chlorophyll a is an important indicator to evaluate the degree of eutrophication of water bodies and also the main factors of primary productivity state of the oceans. The coastal zone imager (CZI) onboard the Chinese Haiyang-1C (HY-1C) satellite has an advantage observation in high temporal and spatial resolution. In this study, a chlorophyll a concentration retrieval model for CZI onboard the HY-1C satellite is developed from the in-situ measurements in the East China Sea and the South China Sea. The chlorophyll a concentration is retrieved by the model in the measured waters and compared with MODIS chlorophyll a concentration. The chlorophyll a concentration also retrieved in the Zhujiang River Estuary, Changjiang River Estuary and Bohai Bay. The correlation coefficient between the predicted value of the model and the in-situ chlorophyll a concentration is 0.774 3, the average relative error is 24.58%. The accuracy of the model is verified with the in-situ measurements with the correlation coefficient of 0.993 9 and the average relative error of 18.49%. The distribution of chlorophyll a concentration retrieved from CZI is nearly the same as that of MODIS. The chlorophyll a concentration decreases gradually from northwest to southeast and the peak value locates on the west bank of the Zhujiang River Estuary. The inversion of chlorophyll a concentration in Changjiang River Estuary and Bohai Bay accords with the actual situation. The work in this study indicates that HY-1C satellite coastal zone imager data are useful for the monitoring of coastal ocean color in China.

Through the analysis of the δ¹³C, δ¹⁸O, δ¹¹B, δ³⁷Cl isotopes and Cl⁻, ${\rm{SO}}_4^{2-} $, K⁺, and Na⁺ ion index in the sediment pore water of the core GSW1 in the East China Sea outer Slope-Okinawa Trough, the changes of early diagenesis, fluid sources, migration and oxidation environment of sediments were discussed. The results show that the pore water dissolved inorganic carbon of the core GSW1 mainly comes from sea water and organic matter, the concentration of ${\rm{SO}}_4^{2-} $ decreases more gently with depth, and the concentration of Cl⁻ is much lower than seawater. The sulfate consumption in the surface sediments of this pore is mainly caused by organoclastic sulfate reduction (OSR) controlled, anaerobic oxidation of methane (AOM) occurs in deeper layers below 4 m. The H₂S produced by OSR diffuses upwards and is enriched and oxidized, which is the main factor that causes the 110−360 cm ${\rm{SO}}_4^{2-} $ content to not significantly decrease. The overall trend of pore water ${\rm{SO}}_4^{2-} $ concentration decreases with depth, indicating that the deposition environment of core GSW1 has gradually changed from an oxidizing and sub-oxidizing environment to a reducing environment. The vertical changes of δ¹¹B and δ³⁷Cl fluctuate greatly. On the one hand, they are affected by the degradation of organic matter in the early diagenesis stage, and they may also be related to the diffusion of pore fluid and sediment/pore water interaction.

In this study, Argo surface salinity, OSCAR current and other data are used to explore the influence of oceanic advection transport on the surface salinity in the Tropical Indian Ocean based on the advection term of the salinity budget equation. The adjustment mechanism of the spatial structure of surface salinity by oceanic advection is revealed by freshwater transport calculation along 6 key sections. The results show that the oceanic advection which transports the high-salinity water in the Equatorial Western Indian Ocean (EWIO) and the Arabian Sea (AS) to the Equatorial Eastern Indian Ocean (EEIO), the Bay of Bengal (BOB) and the Andaman Sea, and also transports the low-salinity water in the EEIO, the BOB and the Andaman Sea to the EWIO, the AS and the Equatorial Southern Indian Ocean, plays a role in adjusting the basic balance of salinity in the Indian Ocean. The analysis of freshwater transport along sections shows that the inconsistency between the center of high precipitation and low salinity in the western sea area of Sumatra, and the inconsistency between the center of high evaporation and high salinity in the western sea area of Australia, are both caused by oceanic advection. In summer, the high-salinity water in the EWIO and the AS transported by the southwest monsoon forced circulation into the BOB, is the main reason for the high surface salinity in the BOB.

Based on the latest measured high-resolution shallow profile and multibeam bathymetric data in the West Philippine Basin in 2018, the marine geological disasters in the central rift and surrounding areas of the West Philippine Basin is analyzed in this paper. In the study area, two types of disaster geological factors are identified: one is destructive geological factors, mainly including landslide, active fault, gully and magma diapir; the second is the restrictive geological factors, mainly seamounts, scarps and trenches. Based on the shallow seismic profile, the type, shape and internal structure characteristics of geological hazards bodies are described in detail. The distribution area and development characteristics are discussed. The main inducing factors and adverse effects of geological hazards are discussed. The identification of geological hazards, the delineation of distribution range and the analysis of causes in the study area can provide important geological basis for marine engineering construction, equipment design and maritime navigation, avoid adverse effects and make risk prediction in advance.

In order to investigate the tolerance of temperature and salinity of Tapes dorsatus juveniles, ecological methods with the laboratory controlled system was used in this study. The results showed that: (1) in the temperature tolerance test, juveniles maintained 90%−100% survival rate at the low-temperature groups (4℃, 6℃, 8℃ and 10℃) for 0 d, 2 d, 3 d and 7 d and at the high-temperature groups (33℃, 34℃, 35℃ and 36℃) for 5 d, 4 d, 1 d and 0 d, respectively; (2) under temperature stress, at the low-temperature groups, the semilethal temperatures at 48 h, 96 h, 144 h and 192 h were 5.02℃, 7.68℃, 9.01℃ and 9.20℃. And in the high-temperature groups, the semilethal temperatures at 48 h, 96 h, 144 h and 192 h were 35.44℃, 34.74℃, 34.43℃ and 34.25℃, respectively. In the salinity tolerance test, (1) juveniles maintained 90%−100% survival rate at low-salinity groups (13.0, 15.6, 18.2, 20.8 and 23.4) for 1 d, 1 d, ≥9 d, ≥9 d and ≥9 d while in the high-salinity groups (41.6, 44.2, 46.8, 49.4 and 52.0) followed by 9 d, 2 d, 1 d, 1 d and 1 d, respectively; (2) the semilethal salinity at 48 h, 96 h, 144 h and 192 h in the low-salinity groups were 14.46, 16.02, 16.76 and 16.91, while in the high-salinity groups were >52.0, 51.79, 50.58 and 48.88, respectively; (3) for survival, the suitable and the optimum salinities of T. dorsatus juveniles were 16.91−48.20 and 18.20−41.60, respectively. For growth, the suitable and the optimum salinities were 23.58−45.15 and 33.90, respectively. The results indicated that T. dorsatus juveniles had strong tolerance to high temperature and were suitable for cultivation with higher temperatures in the southern sea area. The suitable survival salinity range was wide, and the optimal growth salinity was basically the same as the offshore sea water. T. dorsatus juveniles suitable for breeding in the offshore sea water.

In order to understand the community structure dynamics of fish eggs and larvae in the estuarine waters, four surveys were conducted in the coastal waters of the Huanghe River Estuary in June of 2014, 2015, 2017, and 2018. According to the species composition and quantitative distribution of fish eggs and larvae, the resource distribution of fish eggs and larvae in this water area was comprehensively studied by using the methods of biodiversity index, R software clustering and Pearson correlation matrix analysis. The results showed that a total of 3 829 fish eggs and 234 larvae were collected during the four surveys by horizontal trawl with plankton net. The obtained fish eggs and larvae belonged to 7 orders, 14 families and 15 genera. The dominant species of eggs were Engraulis japonicus and Cynoglossus joyeri. The dominant species of larvae were Konosirus punctatus and Gobiidae sp. All biodiversity indexes were the highest in 2015 and the lowest in 2018. Used the R language to cluster the similarity of the species composition between fish eggs and larvae, and divided the 4 survey years into 3 groups, each grouping the main divergent species were E. japonicus. The results of Pearson correlation matrix showed that salinity was closely related to the biodiversity of fish eggs and larvae. The analysis showed that the annual variation characteristics of community distribution and diversity of fish eggs and larvae in the Huanghe River Estuary and adjacent waters reflected the response of fish to environmental variation.