The present study is concerned with the analytical solution for waves propagating over a local permeable seabed and wave reflection and transmission by the local permeable seabed. The computational domain is decomposed into four subdomains of which the middle subdomain is permeable, with the porous seabed beneath it, and the left and right subdomains are impermeable. Applying the linear wave theory, the velocity potential of each fluid subdomain is set up, including the effect of evanescent mode, and the pressure inside the porous seabed is given. The unknowns are solved by the continuous conditions at the interfaces between the neighboring subdomains. The effect of permeability coefficient, water depth and length of permeable seabed on wave transformation is discussed. The results indicate the wave height attenuates increasingly with the increase of permeability coefficient, the length of permeable seabed, and decrease of water depth. Wave reflection and transmission will occur due to the local permeable seabed. The reflection coefficient oscillates, and tends to be constant eventually, while the transmission coefficient reduces exponentially, and tends to be zero with the increase in the length of permeable seabed.

Particle filter (PF) is a very promising nonlinear data assimilation method. However, due to the particle degeneracy problem, it has not been widely used in large geophysical models. In contrast, the ensemble Kalman filter (EnKF) and its derivative methods have been widely used in operational data assimilation systems in recent years. A newly proposed local particle filter (LPF) which employs the localization technique in particle filter, can effectively avoid the degeneracy problem with low computational costs and has great potential for practical applications. In this paper, data assimilation experiments using LPF and EnKF are conducted in a fully coupled Community earth system model. The sythetic satellite sea surface temperature data are assimilated with each method. Different impact of local parameters on each method is investigated, and the data assimilation performances of LPF and EnKF are compared. The comparison results show that the performance of LPF is more sensitive to localization parameter. With the optimal localization strategy, it is shown that LPF can be better than EnKF, and have a potential to be further improved.

The scatterometer onboard China-France oceanography satellite (CFOSAT) uses rotating fan beams to measure sea surface radar backscatter values at different incidence and azimuth angles. The backscatter measurements of CFOSAT scatterometer (CSCAT) are with relatively high spatial resolution. Therefore, it presents unprecedented opportunities for retrieving offshore wind fields. This paper introduces the main procedures as well as the key techniques of the coastal wind retrieval for CSCAT. In particular, a box-window is used to aggregate the high-resolution backscatters (namely slices in the level 1B data) into a certain wind vector cell (WVC) before performing the wind inversion. The coastal winds derived from the advanced scatterometer (ASCAT) and the QuikSCAT scatterometer are then used to verify the results of CSCAT coastal wind retrieval. It shows that the CSCAT winds are of good quality over the sea surface with offshore distance larger than 40 km, but degrades rapidly in quality for WVCs with offshore distance below 40 km. Further analysis indicates that the degraded statistical scores are mainly caused by some outliers that may be contaminated by the sea ice. In general, the CSCAT offshore winds are in good agreement with both the model forecasts and the buoy winds.

To study the effect of hypoxia on immune function of juvenile cobia (Rachycentron canadum), the transcription level of immune related genes were detected in gills, liver, intestines, and spleen after exposing to (3.15±0.21) mg/L hypoxia stress for 28 d. The results showed: (1) in gills, the transcription level of tumor necrosis factor α (TNFα) and type 2 interleukin-1 receptor (IL-1R2) extremely decreased (p<0.01) on 1 d and 14 d of stress. On 28 d of stress, TNFα extremely decreased (p<0.01) while IL-1R2 significantly decreased (p<0.05). Tumor necrosis factor alpha induced protein 3 (TNFAIP3) extremely increased (p<0.01) on 1 d and then significantly decreased (p<0.05) on 7 d and extremely decreased (p<0.01) on 14 d. Interleukin-1β (IL-1β) extremely decreased (p<0.01) on 1 d and then extremely increased (p<0.01) . Interleukin-17C (IL-17C) extremely decreased (p<0.01) on 7 d and 14 d, while heat shock protein 70 (HSP70) significantly decreased (p<0.05) on 1 d and extremely decreased (p<0.01) on 14 d and 28 d. (2) In liver, the transcription level of TNFα and IL-1R2 significantly decreased (p<0.05) on 1 d and 28 d and extremely decreased (p<0.01) on 14 d. TNFAIP3 extremely increased (p<0.01) on 1 d and extremely decreased (p<0.01) on 14 d and 28 d. IL-1β extremely increased (p<0.01) at all stress time points, while IL-17C extremely decreased (p<0.01) on 7 d, 14 d and 28 d. HSP70 continued to increase and reached the maximum on 28 d (p<0.01). (3) In the intestine, the transcription level of TNFα, IL-1β, IL-1R2, IL-17C and HSP70 genes were higher (p<0.01) than those in the control group at all stress time points. TNFAIP3 extremely increased (p<0.01) on 1 d and significantly decreased (p<0.05) on 7 d and extremely decreased (p<0.01) on 14 d. (4) In spleen, the transcription level of TNFα and IL-17C extremely decreased (p<0.01) on 1 d, 7 d, 14 d and significantly decreased (p<0.05) on 28 d. IL-1β extremely decreased (p<0.01) on 1 d, 28 d and significantly decreased (p<0.05) on 7 d and 14 d. IL-1R2 extremely decreased (p<0.01) on 1 d, 7 d, 28 d and significantly decreased (p<0.05) on 14 d, while HSP70 extremely decreased (p<0.01) on 1 d, 7 d and 28 d. The results indicated that immune genes of transcription level in juvenile cobia showed significantly change after 28 d of hypoxia stress, suggesting that long-term hypoxia may inhibit the immune function, cause intestinal inflammation, and increase the risk of pathogen infection in cobia.

As a typical high-turbidity bay, the carbonate systems in the Hangzhou Bay are not well documented. In this paper, the spatial distributions of inorganic carbonate paramenters in the Hangzhou Bay were analyzed based on data collected from two summer surveys in 2018 and 2019. The results showed that dissolved inorganic carbon (DIC) concentration and total alkalinity (TA) in surface layer of the Hangzhou Bay ranged from 1 553 μmol/kg to 1 964 μmol/kg and from 1 577 μmol/kg to 2 101 μmol/kg, respectively, which were lower than that of the Changjiang River Estuary (1 407−2 110 μmol/kg and 1 752−2 274 μmol/kg). The spatial distributions of DIC concentration and TA were controlled by the mixing of fresh water and offshore sea water. They were affected by strong tide, which gradually increased DIC concentration from inner bay to outlet of the bay. Air-sea carbon exchange and biological respiration led to decrease and increase of DIC concentration, with the contributions of (−42.3±11.7)% and (34.2±14.3)%, respectively. Such two compensate processes resulted in a net balanced state. The average surface pCO₂ in the Hangzhou Bay was 799 μatm (675−932 μatm), indicating that bay waters were source of atmospheric CO₂. The revelle factor in the Hangzhou Bay varied from 12.8 to 23.8, suggesting a weaker CO₂ buffering capacity than the adjacent East China Sea (the mean value was 11.9). Compared with other estuaries/gulfs, the characteristics of high turbidity and strong tides in the Hangzhou Bay made the spatial distributions of the carbonate system in the bay water had regional specificity.

The composition and distribution of mangrove species are crucial to the protection and restoration of mangrove wetland ecosystems. In this study, mangrove species distribution was identified by unmanned aerial vehicle (UAV) hyperspectral images from Zhangjiangkou mangrove national nature reserve. Spectral characteristics, spectral differential, and spectral continuum removal were analyzed, 17 spectral parameters of 911 group spectral data from different vegetation species were obtained. Furthermore, 13 parameters for decision tree construction were selected by stepwise discriminant analysis. As a result, an accurate distribution map of mangrove species in the study area was obtained through C5.0 decision tree classification model. The vegetation species present different distribution types from top to bottom in the Zhangjiangkou mangrove national nature reserve. The upper part of the study area was dominated by the mixed type of Aegiceras corniculatum and Kandelia obovata. The middle area showed symbiosis status of three different mangrove species Avicennia marina, Aegiceras corniculatum and Kandelia obovata. The lower part of the study area was dominated by Avicennia marina, and a small amount of Kandelia obovata. Through the confusion matrix, the overall classification accuracy is 87.95% and the Kappa coefficient is 83.81%, showed a satisfactory precision. Therefore, our mangrove species identification results from UAV hyperspectral images could be used as a reference for ecological protection of regional mangrove wetland, and also as a identification method reference for mangrove species.

In order to understand the population dynamics of ichthyoplankton and the changing laws of biodiversity in the Laizhou Bay, four investigations (respectively in spring, summer, autumn and winter) of 20 positions in the Laizhou Bay from 2014 to 2015, the seasonal variations of species composition and community structure of ichthyoplankton in this area, involving its dominant species, community diversity and seasonal turnover rate were studied in this paper. The results showed that 135275 fish eggs and 2456 larvae were collected, total 22 species. Main species of ichthyoplankton changed significantly with the seasons, from Engraulis japonicus and Liza haematocheilus in spring, to Thryssa kammalensis and Allanetta bleekeri in summer, to Protosalanx hyalocranius in autumn, to Zoarces elongates in winter. The richness index (D) and diversity index (H′) were the highest in summer, and the evenness index (J′) was the highest in autumn. The species turnover rate from spring to summer was the lowest. Analysis of the results of clustering using R language with the highest likelihood suggest the existence of three assemblages of ichthyoplankton in the surveyed waters: spring group, summer and autumn group, winter group. The main divergent species of spring group and summer-autumn group, spring group and winter group were Engraulis japonicus. While the main divergent species of summer autumn group and winter group were Zoarces elongates and Thryssa kammalensis. This study shows that there are significant seasonal differences in the species composition, quantity distribution and biodiversity of ichthyoplankton in the Laizhou Bay. The research results supplement the basic data of fish early replenishment resources in the Laizhou Bay and provide basis for fishery resources conservation in the Laizhou Bay.

Salinity is an important parameter to characterize physical and biogeo-chemical processes. Optical satellite images with high resolution can avoid radio frequency interference, and provide a feasible way to monitor sea surface salinity (SSS) in coastal regions. Using an extensive dataset of ship-based SSS and MODIS estimated remote sensing reflectance (Rrs) at 412 nm, 443 nm, 488 nm, 555 nm and 667 nm and sea surface temperature (SST) a random forest (RF) model has been utilized to retrieve the SSS. Based on the predicted SSS, we analyze the spatiotemporal heterogeneity of SSS in the Gulf of Mexico and contribution of each factor with correlations coefficient. The results show that: (1) the RF model can accurately estimate the SSS in the Gulf of Mexico (RMSE=0.335, R²=0.931); (2) the spatial distribution pattern of SSS shows a ring-shaped inward value increase, which is affected by river discharge, wind forcing and circulation; (3) there is a strong correlation between SSS and SST, and SST significantly impact in retrieving SSS; (4) the correlation between SST, Rrs and SSS appears spatial heterogeneity.

The cumulative human impact assessment of marine ecosystems is an ecological method to scientifically recognize the response and feedback laws of the system to external disturbances. In order to explore and reveal the inherent mechanisms, the region of coastal seas of China as the research scope in this article, selecting 16 ecological factors in four aspects, marine fishery, marine shipping, land-based and offshore pressures, and climate change. And by spatial quantization and standardization, the cumulative exposure and impact assessment of the 9 marine habitat types in the study area are carried out under the 1 km×1 km spatial grid scale. The results show that the cumulative exposure in the study area is generally higher in the coastal seas than in the pelagic, and gradually decreases to the far ocean; the coastal seas ecosystem is mainly affected by land-based pollution and fishing, and overall climate change contributes the most; 22.8% and 7.6% of China’s coastal seas are respectively highly and extremely highly affected, among which the Changjiang River Delta is the most affected by human activities.

The CO₂ flux at the sea-air interface, which is equal to the product of the gas transfer velocity, solubility, and the CO₂ partial pressure difference between sea and the atmosphere, is estimated using the bulk equation, where the gas transfer velocity is usually associated with the wind speed. Different authors have proposed different parameterization schemes, in which the gas transfer velocity is a polynomial of different powers of the wind speed. In this paper, we summarize the main findings on the gas transfer velocity as a function of wind speed. We discover that the observation method has a greater influence on the gas transfer velocity than the power of the wind speed polynomial. On this basis, this paper calculates the global CO₂ flux from 1982−2018 using several different parametric formulas for the gas exchange rate. The ocean is a sink for atmospheric CO₂, the equatorial sea area is a source, and the ocean near 40° in the northern and southern hemispheres forms a strong absorption zone along the latitudinal direction. The annual average value of oceanic CO₂ absorption (in terms of carbon) over 1982−2018 is (−1.53±0.15)Pg/a. The oceanic absorption decreases year by year until 1999, reaching a minimum in 1999, after which the oceanic absorption begins to increase, with the increase in oceanic absorption occurring mainly in the Southern Ocean.