By using the beach monitoring technologies such as Unmanned Aerial Vehicle (UAV) and elevation monitoring equipment, the monitoring data of Haiyang beach before and after Typhoon Lekima (No.1909) were obtained, the morphology changes, erosion and accretion variation of beach profiles during Typhoon Lekima landing were analyzed, and the response of beach evolution to the typhoon was discussed. The result shows that beach morphology evolution after the typhoon is mainly including the expansion of the aeolian dune area, erosion of the beach surface in the high-middle tidal zone, micro-topography disappearance and so on. The typhoon mainly affected the beach by erosion, resulting in an erosion volume about 2.43×10⁴ m³, which mainly occurred on the high tide zone. The aeolian dunes were weakly silted, but some of them were eroded seriously. The backshore was weakly silted because of sand deposition from strong wind and alluvial flow. In the middle and low tide zones, beach morphology changes were mainly controlled by the beach surfaces lope, which was manifested as erosion with high slope, weak deposition with low slope, and several small sandbanks formed after the typhoon. On the whole, the typhoon impacts on the beach evolution mainly lead to the sediment budget deficit, and further exacerbated the erosion of Haiyang beach.

Tropical cyclone is one of the most active dynamic factors for beach evolution. However, there are few field observations of beach during storms due to terrible working conditions. In this paper, 6 and a half days of high-frequency observation during the Typhoon Bebinca was conducted at the Qing’an Bay beach. The observation data included full-time hydrodynamics and 164 groups hourly variation of beach surface elevation. Three main analysis results were identified: (1) Controlled by the spatial distribution of Hainan Island-Leizhou Peninsula and the changeable track of the Typhoon Bebinca, the storm surge was maintained between 0.38−0.5 m, the wave height first decreased from 0.78 m to 0.43 m and then increased to 0.56 m. (2) The beach berm was eroded and a sand bar was formed under the water. There were three response stages of the beach berm during the Typhoon Bebinca, eroded downward fast, eroded slowly to the maximum, and recovered by oscillating deposition. The recovery amplitude could reach one quarter of the maximum erosion depth during the Typhoon Bebinca. (3) The response process of the Qing'an Bay beach to Typhoon Bebinca was mainly composed of four modes. The first mode reflected the erosion process of the spring tidal beach berm and the formation of the sand bar. The second mode indicated the erosion of the storm beach berm, the compensatory recovery of the spring tidal beach berm and the growth of the sand bar. The third mode revealed the bilateral transport process of sediment caused by the uprush and undertow at the secondary breaking position of waves. The fourth mode showed that the strong waves suspended the sediment in the surf zone, and some of the suspended sediment which was transported to the deep-water area by littoral current and offshore current may lost permanently.

Using the Finite-Volume Community Ocean Model (FVCOM) numerical model, considering the combination of parameterization of internal tidal dissipation and self-attraction and loading tide in the unstructured mesh model for the first time, a total of six tide-generation forces including M₂、S₂、N₂、K₁、O₁、Q₁ are established to drive the global forward tidal model. Based on the verification of the global tidal model results, we calculate and statistically estimate average density of the global tidal current energy, and show the tidal current energy distributions where there is greater tidal current energy in the world. The results show that there is a large tidal current energy belt with an area of nearly 33 000 $ {{\rm{k}}{\rm{m}}}^{2} $ and a maximum tidal current energy density of 1 100 $ {\rm{W}}/{{\rm{m}}}^{2} $ in the English Channel. The maximum tidal current energy density in the western side of Baffin Island in Canada exceeds 1 150 $ {\rm{W}}/{{\rm{m}}}^{2} $. The maximum tidal current energy density in the Cook Bay waters of Alaska is 500 $ {\rm{W}}/{{\rm{m}}}^{2} $. The tidal current energy belt at the entrance to the White Sea in Russia is large, where the maximum tidal current energy density reaches 500 $ {\rm{W}}/{{\rm{m}}}^{2} $. Australia's coastal tidal current energy belts have small area but large amount, and their tidal current energy density generally exceed 100 $ {\rm{W}}/{{\rm{m}}}^{2} $. In China's offshore waters, the tidal current energy density in the Hangzhou Bay waters of the Changjiang River Estuary and the north of Taipei reaches 100 $ {\rm{W}}/{{\rm{m}}}^{2} $.

Based on the fishery resources survey data in the outer waters of the Zhoushan Islands in April (spring) and October (autumn) 2018, the composition, quantity distribution and dominant species of fishes were analyzed, and the relationship between them and hydrological environment was analyzed by the CCA method. The results showed that there were 106 species of fish in the waters outside Zhoushan Islands, belonging to 12 orders, 47 families and 80 genera. The fish mass densities in spring and autumn are 210.50 kg/km² and 829.06 kg/km² respectively, and the abundance densities are 8.08×10³ ind/km² and 165.94×10³ ind/km² respectively. The density of fish resources in spring is higher in the northwest sea area and lower in the east sea area of the investigated sea area, while the density of fish resources in autumn is higher in the east sea area and lower in the northwest sea area. The dominant species of fish change substantially between the two seasons. The dominant species in spring and autumn were Lophius litulon、Lepidotrig lajaponica、Apogon lineatus and Apogon lineatus、Acropom japonicum. The number of fish species showed significant seasonal and spatial changes, and the number of fish species is higher in the west and northwest near the coastal islands, with most fishes inhabiting in waters with water depth of 50−80 m. The results showed that the spatial and temporal separations of fish communities were obtained from CCA analysis. Surface temperature, bottom temperature and surface salinity were the key environmental factors that affected the composition and quantity distribution of fish species in the sea area under investigation. The strong correlation between fish community and environmental factors reflected the climate change effect on the separation of fish species.

As one of the forms of land-ocean interactions, submarine groundwater discharge (SGD) can release solutes into the coastal sea and has a significant impact on the nutrients budget in coastal seawater. Here, using ²²²Rn tracer, the SGD and the associated dissolved inorganic carbon (DIC) and dissolved organic carbon (DOC) inputted to the Zhenzhu Bay, a typical mangrove-dominated bay, were quantified. The results show that the average concentrations of ²²²Rn, DIC and DOC in groundwater are relatively higher than those in river water and surface sea water. A ²²²Rn mass balance implies that SGD rate is (0.36±0.36) m/d during January 2019. And SGD-derived DIC and DOC fluxes are estimated to be (2.41±2.63)×10⁷ mol/d and (1.96±2.20)×10⁶ mol/d. It confirmed that SGD-derived carbon is the most important carbon source in this bay, with 91% DIC and 89% DOC of the total input fluxes by SGD, respectively. Our results highlight the importance of groundwater-derived carbon fluxes in the Zhenzhu Bay, especially in the blue carbon assessments and biogeochemical process in tidal zones such as mangrove ecosystems.

Surface sediments were collected by high-resolution sampling from the Changjiang River Estuary and its adjacent shelf in March, 2014. Grain size composition, Specific Surface Area (SSA), Total Organic Carbon (TOC) and stable carbon isotope composition (δ¹³C), n-alkanes and its related indices in sediments were analyzed to discuss the high-resolution distribution patterns of sedimentary organic carbon (OC) and n-alkanes in this region. A three end-members mixing model based on Principal Component Analysis (PCA) and Monte-Carlo Simulation was constructed to characterize the sources of sedimentary OC quantitatively. The results showed that TOC contents were 0.45%±0.16%, which were relatively higher in coastal mud area than offshore sandy area. Absolute contents (Σn−Alk) and relative contents (Σn−Alk/TOC) of total n-alkanes (C₁₄ to C₃₅) were (1.42±0.73) μg/g and (0.34±0.21) mg/g , respectively. There was a strong odd to even carbon preference of long-chain n-alkanes in muddy sediments, while there was an even to odd carbon preference of short-chain n-alkanes in sandy area. Inputs from the Changjiang River, the Old Yellow River Estuary and small rivers in the Zhe-Min coasts and hydrodynamic sorting restricted the transport and dispersal patterns of n-alkanes. The results of the three end-members mixing model indicated a mixture input of marine, soil and higher plant derived OC in this region. Among them, sedimentary OC was dominated by marine source (42.70%±18.18%), increasing from coast to outer sea gradually. Contributions of soil OC and higher plant OC were 28.99%±15.37% and 28.31%±17.12%, respectively. Influenced by hydrodynamic forces, obvious differentiation of these two terrestrial OC pools occurred during transport after entering into ocean. Soil OC was mainly associated with fine grains, and was transported southward along the Zhe-Min coast, while higher plant derived OC was mainly transported along northeast direction in the Changjiang River Estuary.

Sea surface partial pressure of carbon dioxide (pCO₂) is a crucial parameter for estimating ocean carbon source and sink term, but its sparse and uneven in situ measurements in space and time lead to large uncertainty in the estimate of sea-air CO₂ flux and characteristics of ocean carbon source and sink. To eliminate this uncertainty, a general regression neural network approach using the Surface Ocean CO₂ Atlas (SOCAT) dataset, based on the non-liner regression of pCO₂ and longitude, latitude, time, temperature, salinity and concentration of chlorophyll, was successfully used in the reconstruction of global 1°×1° resolution monthly sea surface pCO₂ from 1998 to 2018, with a root mean square error (RMSE) of 16.93 μatm and a mean relative error (MRE) of 2.97%, lower than existing feed-forward neural network (FFNN), self-organizing neural network (SOM) and machine learning approaches. The global distribution of pCO₂ obtained by this approach agrees well with existing researches.

The n-alkanes and fatty acids were analyzed in two sediment cores at the upwelling edge region (Station S5) and center area (Station S10) of eastern Hainan Island, the source and degradation characteristics of organic matter were comprehensively analyzed by combining organic carbon content, particle size, carbon stable isotope (δ¹³C) and other parameters. The interannual variation of upwelling intensity in the study area was reconstructed using the diatom abundance parameter ∑16∶∑18 of fatty acids. The grain size results show that Station S10 is located near the center of upwelling, with coarse grain size and mainly sand; Station S5 is located at the edge of upwelling, with fine grain size and mainly silt. The δ¹³C and fatty acids parameter (∑C_20-:0/∑C_20+:0) of the two stations show that both stations are dominated by marine source input. The degradation degree of organic matter in Station S10 is greater than that in Station S5 . The diatom abundance parameters of fatty acids and the percentage of phytoplankton fatty acid indicate the primary productivity of Station S10 is higher than Station S5, and ∑C₁₆∶∑C₁₈ is used to indicate the interannual variation of the intensities of the upwelling in the study area; the upwelling intensity shows weak, strong, and weak signals between 1925−1950, 1950−1980, and 1980−2008. It is consistent with the interdecadal trend of Pacific Decadal Oscillation. El Niño-Southern Oscillation may regulate the upwelling intensity in a short time scale, while in a long time scale, it may be mainly regulated by Pacific Decadal Oscillation.

The metal contents in the core sediments collected from the Daya Bay, a typical marine environment in the Guangdong-Hong Kong-Macao Greater Bay Area were measured in this study. National standard for marine sediment quality and fuzzy comprehensive assessment were applied to evaluate the historical evolution of the sediment quality in the past one hundred years. Our results indicate that the metal contamination in the bay experienced three major stages: (1) Before 1980s, the concentrations of most metals were low and the sediment quality fell into the category of class I. Accordingly, the metal risk was low in this period. Cr contributed most and Cd contributed least to the risk, respectively. (2) Between 1980 and 2000, the metal contents were significantly higher than the background values, suggesting that there was a sharp increase of metal input. The category of sediment quality fell down to class II and class III. However, the sediments in the margin areas of the Daya Bay were only slightly affected and still belonged to class I quality. Cu acted as a major metal pollutant instead of Cr in this period. (3) After the year of 2000, the metal levels and the metal risk decreased sharply. The sediment quality recovered back to class I and Cr contributed most to the risk at the time.

Antarctic red algae play important roles in the coastal ecosystems and industrial applications. Meanwhile, their unique physiological acclimation mechanisms to the extreme environments endow them to be ideal organisms for discovering new genes and new metabolic pathways. In this study, we sequenced the transcriptomes of Antarctic red algae Iridaea cordata (Turner) Bory and Curdiea racovitzae Hariot, and compared with their moderate temperature close relatives. The transcriptome sequences of I. cordata and C. racovitzae were assembled into 14055 and 12006 Unigenes, with an average length of 1473 bp and 1448 bp, respectively. The Lhca2, Lhca6 and Lhcb genes homologous to the green algae genes were found in I. cordata transcriptome while not in other red algae. Lhcf gene encoding fucoxanthine and Chl a/c binding protein presenting in brown algae and diatoms were identified in both I. cordata and C. racovitzae. Photolyase repairs UV-induced DNA damages. 6-4 photolyase, CPD I and CPD II genes were identified in the transcriptome of I. cordata, while only CPD II gene was found in the transcriptome of C. racovitzae. Although the functions of those specific genes in Antarctic red algae are expected further investigation, our study provides a foundation for the following researches on the acclimation mechanisms of seaweeds to the extreme light environments in Antarctica.