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 The temporal and spatial change characters of coastline and tidal flat in the islands with different principle functions in the Zhoushan Archipelago were analyzed, using a coastal remote sensing monitoring dataset with 30 m spatial resolutions at annual interval from 1986 to 2017. The results suggested that the coastlines in Zhoushan Archipelago advanced toward the sea, with many water areas(152 km2) and tidal flats(18 km2) reclaimed into lands and the government policies were the main driven factors. The change characters were various among the islands with different principle functions. In particular, the land reclamation was significant in the islands with the principle functions of comprehensive development, coastal industry, coastal tourism, and harbor and logistics, accounting for 96% of the archipelagos new lands. The land reclamation was slight in the islands with marine science and education and scientific fishery functions, accounting for 4% of the archipelagos total new lands. Meanwhile, the coast was stable and well protected in the islands with ecological conversation and clean energy functions. The results could provide scientific basis for coastal zones ecological protection and restoration projects, as well as the marine principle functional zoning.

Sea surface temperature (SST) is the critical factor for depicting the marine thermal distribution. Daily global SST data sets support the typhoon elaborated monitoring and other marine disasters forecast. SST products retrieved by the visible infrared radiometers and mediumresolution imagers have high spatial resolution, while the SST products retrieved by infrared remote sensing are affected by clouds, fog and haze, and therefore a large areas under the clouds are lack of value. SST products retrieved by the microwave radiometer have low spatial resolution, while the microwave could penetrate the cloud layer to achieve all-weather sea surface observation. The data interpolation empirical orthogonal function method (DINEOF) was used to reconstructed the global SST products, and FY-3 (Fengyun 3) SST data sets were applied in this study, which included the SST data sets from the FY-3B/FY-3C Visible and Infra-Red Radiometer, FY-3D Medium Resolution Spectral Imager and FY-3D Micro-Wave Radiation Imager. Accuracy of the reconstructed data sets was verified using OISST measurements to demonstrate the validity and reliability of the DINEOF method. The results show that DINEOF reconstructed sea surface temperature (DSST) data are validated reliable. Root mean square error of the original data is ranging from 0.59 ℃ to 0.70 ℃, while the reconstructed data is relatively stable, ranging from 0.10 ℃ to 0.34 ℃. Correlation coefficient obvious raises from 0.33-0.48 to 0.78-0.98. Multi-sensors reconstructed SST products is continuous and credible in spatial distribution and monitor the variation of warm pool from spring to winter. Addition of FY-3D microwave SST products has significantly improved the spatial continuous distribution and temporal resolution of reconstructed SST.

Marine gas hydrate deposits are significant temporal reservoirs for hydrocarbons migrating from deep sources. This is crucial to our understanding of ocean carbon cycling. The cold seep, a geological process regarding gas leakage from deep or shallow sources, is usually linked with gas hydrate decomposition. In this thesis, we reviewed the latest applications of in situ monitoring and detecting methods regarding the leakage plumes, migration pathways, and seafloor geomorphologies associated with gas hydrate and cold seep systems, primarily including vessel-and land-based gas plume measurements, surface ocean-lower atmosphere hydrocarbon emission detections, seafloor visualization techniques, and in situ observation networks. The integrated applications of these in situ observation methods provide a nuanced view of the temporal and spatial variability of hydrate and cold seep systems, facilitate understanding of the fate of hydrocarbons, and expand our knowledge of cold-seep biota in a watery desert.

There is strong tide in the Changjiang (Yangtze River) Estuary and its adjacent area. Except for the coast area, there is a lack of longterm tide level and tidal current data in the offshore area. Long time series of water level observation data was used in this study, and the results reveal that the tidal type in the Changjiang Estuary is a regular semidiurnal tide, with a significant shallow water division in the nearshore area; the M2 division is the most significant semidiurnal tide, and the amplitude tends to increase from the open sea in the east to the shallow water or island group at the mouth of Hangzhou Bay in the west. The M2 tidal current is the most significant semidiurnal tidal current, and the rotating tide is the most significant semidiurnal tide. The two stations to the south of the Changjiang mouth are rotating counterclockwise, while the stations to the east of the mouth are rotating clockwise. The vertical structure of the tide has significant spatial differences, the ellipticity of the M2 tidal current is mostly negative, the ellipticity of the M2 tidal current, the direction and the arrival time of maximum velocity all vary significantly with depth.

The Landsat TM/OLI remote sensing images from 1973 to 2018 were obtained as the data source by using the remote sensing and GIS technology. Based on the geographical background information, the spatial and temporal evolutions of the coastline in the Pearl River Delta region over 45 years were analyzed. The results show that the Pearl River Delta changed significantly, a large number of muddy coast changed into urban industrial coast and port coast. The artificialization index of Pearl River Delta coastline was rising, the types of coastline were developed in a diversified direction, the total length and fractal dimension of shoreline were increasing continuously, the main factors of increase shoreline length and fractal dimension were port construction, coastal industrial zone and reclamation.The evolution of the coastline had obvious regional characteristics, and the regions with large changes were mainly concentrated in Shenzhen Mirs Bay, Guangzhou Nansha and Zhuhai Doumen. From the perspective of the main structure of shoreline, each region presented different type changing tendency, substituted the natural shoreline, the industrial and port shorelines became the main type in each region. The intensity of development and utilization was increasing in various regions, among which the intensity of development in Shenzhen was growing the fastest. Social activities and location policies were the main driving factors for the evolution of shoreline.

The river-estuary-coastal ocean continuum (referred to as the continuum hereinafter) is a transition zone connecting lands and oceans. The carbon budgets in the continuum are dynamic and uncertain components in global carbon budgets. This complex landocean interactive ecosystem can absorb atmospheric CO2 through photosynthesis and dissolution of CO2. Also, the carbon fixed by photosynthesis or chemical weathering in land and watershed can be transported horizontally to the shelf waters and open oceans. In this paper, the progress of carbon cycles in the continuum is reviewed by taking the famous Chesapeake Bay and Changjiang Estuary-East China Sea continuum as typical examples. It is concluded that systematic observation characterized with land-sea coordination, sea-space integration, point-line combination, should be combined with physicalecological numerical simulation to reveal the multiple time-space scale processes. The strategy is generally operable, and the historical retrospective of results is also achievable. Thus, it can be used to clarify the evolution of carbon exchange along the river-estuary-coastal ocean continuum and their influences on carbon budgets under the combined pressures of climate change and anthropogenic activities.

As a key parameter in hydrodynamic and sediment transport models, bottom shear stress is very important to study the initiation and erosion rates of bottom sediment. At present, there are six theoretical methods for calculating bottom shear stress based on field measured flow velocity data: LPmean method, LPmax method, TKE method, TKEW method, RS method and ID method, all of which have their specific applicable conditions. It is very important to select an appropriate method to calculate the bottom shear stress in the shallow water area of estuarine and coastal areas where the actions of current and wave are complex. In this study, one observation site at Dafeng Doulong Port, Jiangsu Province (median particle size: 68.56 μm) and two observation sites at Eastern Chongming Shoal, Shanghai (median particle size: 12.89 μm and 45.02 μm) were taken as examples. Field data were collected using Acoustic Doppler Velocimetry and wave measurement instrument (RBRwave), and the bottom shear stress was calculated by six theoretical methods. The results show that: (1) The LPmean method is affected by the average velocity, the distance from the probe to bed and the strength of waves, which underestimates the bottom shear stress and is not suitable for shallow water environment in intertidal flat; (2) LPmax method and TKE method can overestimate shear stress in shallow water environment of intertidal flat where flow velocity varies greatly and wave action is obvious; (3) TKEW method was modified on the basis of TKE method, which is more suitable for solving the bottom shear stress under strong wave action; (4) The results of RS method are affected by waves, and the results of ID method are more reliable than those of RS method when large waves exist, but ID method will overestimate the bottom shear stress when water depth is insufficient.

The combination of human activities and natural factors has formed the eutrophication of the Changjiang (Yangtze River) Estuary and its adjacent waters, leading to increased hypoxic condition in the bottom water in summer, which has become an important signal of the deterioration of ecosystem health. This paper combs the important understandings gained from the recent studies of hypoxia in this area, analyzes multiscale temporal changes of dissolved oxygen, e.g., focusing on the tidalscale, eventscale, and interannual scale, and factors relevant to stratification and material transport. The relevant mechanisms analyzed includes processes such as the diluted water extension, Taiwan Warm Current, fronts, wind field and tides that affect oxygen consumption or transport process. It is also revealed that the main hypoxia phenomena were separated in the Changjiang Estuary and the coastal waters of Zhejiang Province. The similarities and differences in the formation and evolution of the two hypoxic zones were presented. At present, a solid foundation has been laid for the understanding of the hypoxia occurrence, however due to its multiscale temporal variations, field experiments and quantitative studies should be strengthened from a multidisciplinary perspective, and the longterm evolution trend of hypoxia in this area should also be clarified based on longterm time series monitoring.

While the reclamation project expands the land space to the coastal areas, it will also have a significant impact on the topographic changes of the project sea area. Based on the measured data and the results of the Delft3D mathematical modeling,  taking the eastern sea area of Ruian, Wenzhou as the research area in this study, the characteristics and dynamic mechanism of the topographic erosion and deposition changes caused by the Oufei Tidal Flat Reclamation Project were analyzed. Studies  show that the topography of the sea area has changed significantly after the implementation of the project, but the distribution characteristics of erosion and siltation in different areas are not consistent, and the dynamic mechanisms that cause changes are also different. From an overall point of view, the dominant feature of rising tides in the research sea area has been enhanced, and the coastal sea area maintains an overall siltation situation, and the siltation rate has increased slightly. From a local point of view, the vicinity of the dike bulge is affected by the effect of flip flow, which shows slow erosion, and at the concave corner of the dike affected by the blocking flow effect, it appears as rapid silting. The above results have important reference value for guiding the protection and utilization of Oufei Tidal Flat and other similar tidal flats.

There are abundant mesoscale phenomena in the Bay of Bengal and near the mouth of the bay. In this study, a 2.0 version of the Chelton's data set was used, which can distinguish mesoscale eddies in low-latitude regions, and obtain the genesis distribution of mesoscale eddies by tracing. The northwest sea off Sumatra (the area with 5 °N,94 °E as the core) is an important origin of mesoscale eddies. The eddy tracking of Lagrangian method shows that there were 57 cyclonic and 40 anticyclonic mesoscale eddies in the origin (3°N—6°N, 92°E—95°E) during 19932017. Spectrum analysis indicates that there are two significant periods of 180-day and 360-day in sea surface height anomalies. The dynamic mechanism of mesoscale eddies in this origin is the combined effect of topography and wind field, the Rossby wave propagating westward along 5°N increases instability and triggers the mesoscale eddy generation under the action of the ridge topography. The equatorial wind field is an important source of energy in the origin, and the local wind field can induce the polarity of the mesoscale eddy. This study also reveals the reason why the previous literatures described the northwest sea area off Sumatra as a high eddy kinetic area, but failed to identify many mesoscale eddies.

The UK Met Office EN4 analyses product revealed that the surface area and the volume of the North Pacific subtropical high-salinity center, namely North Pacific Tropical Water (NPTW), decreased in the period of 2000-2008 and 2014—2017, and grew in 2008—2014. The changing period of NPTW was highly correlated with Pacific Decadal Oscillation (PDO). Using the ECCO2 reanalyzing data, the fresh water flux was calculated through the NPTW surface. Our results show that the fresh water flux has less contribution to changes of NPTW, while the horizontal advection contributes significantly to the surface area and volume changes of NPTW, which is related to the northward(southward) swing of North Equatorial Current (NEC) during the PDO positive(negative) phase.

Optical dissolved oxygen sensor based on fluorescence quenching principle can obtain spatiotemporal data of dissolved oxygen in seawater, which is widely used in long-term monitoring of marine environment. However, due to the “storage drift” and “measurement drift” occurring during storage and distribution, it is necessary to calibrate and correct the data drift of the instrument. Existing calibration methods have long cycle and complex operation. In this project, the response characteristics of optical dissolved oxygen sensor in air and water medium were studied, and a field calibration method of optical dissolved oxygen sensor using air medium was proposed, and a two-point calibration model of the instrument was established. Experimental results show that the calibration method can effectively correct the data drift of the dissolved oxygen sensor, and the deviation between the measured value of the sensor and the standard value of Winkler titration is within  ±6 μmol·L-1. This method can realize the convenient and rapid correction of optical dissolved oxygen sensor, avoid the tedious steps of laboratory maintenance, improve the quality of monitoring data, maintain the continuity of monitoring data, and has important application value.

In order to study the deep resistivity structure of intraplate volcanoes and their formation processes, a marine magnetotelluric survey at Suda Seamount in the western Pacific Ocean was conducted. The mainstream data processing method SSMT2000 was used for data processing. The measured data after rotation and the two groups of rotation invariants obtained from the measured data were tested for magnetotelluric response under the assumption of one-dimensional structure, and one-dimensional inversion was conducted for the YX direction data with the best response. Combined with one-dimensional forward modeling and other geological data, the inversion results were comprehensively interpreted. The inversion results show that the thickness of the crust at Suda Seamount is about 21.5 km. The thick volcanic clastic rocks indicate that the formation of Suda Seamount is mainly eruptive and weakly intrusive.

Electrochemical methods are the main methods for measuring seawater pH. The self-developed electrochemical pH sensor is based on iridium metal and its oxide electrode, a method for its calibration and data correction in seawater environment was established and applied for in-situ testing in nearshore and oceanic environments. The instrument calibration includes (1)Selecting appropriate calibration buffer reagents according to the calibration requirements of seawater pH analysis; (2)Preparing calibration buffer system by replacing the commonly used 2-aminopyridine (AMP) solution with standard seawater. Data correction mainly includes temperature background correction and error correction. Insitu testing in the sea area and comparison with other similar instruments show that the error caused by the difference of calibration system can be up to 1.00 pH unit, and the data correction can improve the testing accuracy from 0.10 pH unit to 3.00 pH unit. The calibration and data correction method of the instrument can effectively improve the measurement accuracy of this self-developed pH sensor.

In the past two decades, large scale blooms Prorocentrum donghaiense Lu ( P. donghaiense) have frequently occurred in the coastal water of the East China Sea (ECS). Previous studies have shown that P. donghaiense blooms in the ECS originated from the front of Taiwan Warm Current (TWC) and expanded with its invading inshore. However, little is known about the location where the P. donghaiense blooms firstly occur, as it is limited by the investigation section of previous studies. In this research, four surveys in the East China Sea (24 °N-30 °N) in spring and summer of 2013 were conducted. Results clearly showed that P. donghaiense blooms occurred firstly at the northern end of the Taiwan Strait and spread northward and inshore with the invading of the front of TWC. It was not only confirmed again that the TWC played a seed bank role for P. donghaiense blooms in the ECS, but also confirmed the location where P. donghaiense blooms firstly occurred in the ECS. This research was useful to monitor P. donghaiense blooms and similar algal blooms.

With the increasing saturation of coastal nuclear power plant sites, it is a new idea to select islands as nuclear power plant sites. In view of the problem that the island sites are vulnerable to typhoon disasters, the design basis flood level of the sites is determined by studying astronomical high tide, sea level rise, possible maximum storm surge and maximum typhoon wave. The results show that the astronomical high tide level of 10% superfrequency in this region is 3.14 m and the predicted sea level rise in the next 80 years will be 0.31 m. Based on MIKE21 model, a variety of hypothetical typhoon paths were constructed using tropical cyclone parameters. The northwest moving path of typhoon with 0.5 R (R is the maximum wind speed radius of typhoon) to the left of the site produces the possible maximum storm surge, with the maximum water level of 2.99 m. When the typhoon moves in the direction of west, with R to left of the site, the maximum H _1/100 wave height reaches 8.02 m, especially on the east side of the island, which suffers from severe typhoon wave threats. Considering the superposition of various basis flood factors, the design basis flood level of the island nuclear power plant site reaches 11.25 m. Because the proposed site is located on an island and surrounded by sea waters, compared with other coastal sites, the storm surge level is relatively small, but the impact of waves is more significant.

To investigate monochromatic wave nonlinear characteristics around coral reefs with large surface roughness, laboratory experiments were carried out in a wave flume. A cylinder array was used to model the reef roughness and a series of monochromatic wave conditions were tested. Results show that magnitudes of the wave skewness, the wave asymmetry and the Ursell Number reach their peaks at the endpoint, in the interior and at the stating location of the reef surf zone, respectively. All the three parameters increase with the increasing wave height. Meanwhile, the skewness decreases with the increase of wave period while both the asymmetry and the Ursell Number increase with the increase of wave period. Moreover, the skewness increases with the increase of reef-flat water level while both the asymmetry and the Ursell Number decrease with the increase of reef-flat water level. The deep-water Ursell Number is able to describe the variations of the three examined parameters on the reef flat, and the empirical formulas are finally proposed in this study to predict these parameters.

The polymetallic nodule samples were analyzed for their mineralogical and geochemical features, which were acquired on the northeastern slope of the South China Sea using the ROV named as Sea Dragon III. The results showed that the nodules in the study area were predominantly by rod-shaped with a two-layer structure. The outer layer of the polymetallic nodules was mineralogically and geochemically similar to hydrogenic nodules. While the inner layer was porously and composed of goethite with residual minor pyrite. Geochemically, the inner layer was characterized by high concentration of Fe and As but extremely low concentration of Mn, REE and other elements. The inner layer carbon isotopes ( δ ¹³C ) of sample NH-2 was -30.91‰. The study presented that the early forming process of the nodules was related to the activities of cold seep, but the pyrite was oxidized following the extinction of cold seep. Under the influences of contour current in the area, the ferromanganese oxides continued to grow in the outer layer of the nodules.

Since a diagram depicting "The Great Ocean Conveyor" was first appeared as a logo by Wally Broecker in 1987, how the warmed upper ocean circulation ran through the Indonesian Seas with their complex coastline geometry and narrow passages, known as the Indonesian through-flow, becomes one of the difficult settings in boundary conditions of climate change model. With strong nonlinear effect, a shallow narrow passage forms vertical mixed hotspots on the one hand, and on other hand, it becomes a self-adapted low-pass filter if the tidal resonance units are introduced. Qiongzhou Strait, a sufficient sediment supply and shallow narrow passage for the northern shelf of the South China Sea, is reported with strong tidal current and westward through-flow. And its tidal channel and tidal deltas are maintained by the tidal resonance units introduced themself. Strong disturbances such as typhoon and cold wave can cause storm jet flow through the strait, triggering different high nutrition, algal bloom and hypoxia events over the adjacent Beibu Gulf. Qiongzhou Strait seems to be a noteworthy case of studying how the self-adapted low-pass filter introduced and whether human activities can affect the through-flow on the shallow narrow passages.