Identification of Species in Genus Platycephalus from Seas of China

Platycephalus in Chinese sea area has a high commercial value.However,there were mis-identifications in previous records.In this study,we fully distinguished and diagnosed all five species,Platycephalus indicus,P.cultellatus,Platycephalus sp.,Platycephalus sp.1 and Platycephalus sp.2.The results revealed that P.cultellatus was overlooked by previous ichthyologists.Platycephalus sp.1 was misidentified as P.indicus in reality,and Platycephalus sp.2 only existed in the seas of Japan.Furthermore,morphological,especially phylogenetic analysis indicated that Platycephalus sp.from South China Sea differs from all former known species,which might be a new species.We identified all Platycephalus species in China seas for the first time,which will contribute to local species identification,biodiversity conservation and sustainable exploitation of Platycephalus species.

Temporal and spatial variability of the carbon cycle in the east of China's seas:a three-dimensional physical-biogeochemical modeling study

In the east of China＇s seas, there is a wide range of the continental shelf. The nutrient cycle and the carbon cycle in the east of China＇s seas exhibit a strong variability on seasonal to decadal time scales. On the basis of a regional ocean modeling system（ROMS）, a three dimensional physical-biogeochemical model including the carbon cycle with the resolution（1/12）°×（1/12）° is established to investigate the physical variations, ecosystem responses and carbon cycle consequences in the east of China＇s seas. The ROMS-Nutrient Phytoplankton Zooplankton Detritus（NPZD） model is driven by daily air-sea fluxes（wind stress, long wave radiation, short wave radiation, sensible heat and latent heat, freshwater fluxes） that derived from the National Centers for Environmental Prediction（NCEP） reanalysis2 from 1982 to 2005. The coupled model is capable of reproducing the observed seasonal variation characteristics over the same period in the East China Sea. The integrated air-sea CO_2 flux over the entire east of China＇s seas reveals a strong seasonal cycle, functioning as a source of CO_2 to the atmosphere from June to October, while serving as a sink of CO_2 to the atmosphere in the other months. The 24 a mean value of airsea CO_2 flux over the entire east of China＇s seas is about 1.06 mol/（m^2·a）, which is equivalent to a regional total of3.22 Mt/a, indicating that in the east of China＇s seas there is a sink of CO_2 to the atmosphere. The partial pressure of carbon dioxide in sea water in the east of China＇s seas has an increasing rate of 1.15 μatm/a（1μtm/a=0.101 325Pa）, but p H in sea water has an opposite tendency, which decreases with a rate of 0.001 3 a^（–1） from 1982 to 2005.Biological activity is a dominant factor that controls the pCO_2 air in the east of China＇s seas, and followed by a temperature. The inverse relationship between the interannual variability of air-sea CO_2 flux averaged from the domain area and Ni？o3 SST Index indicates that the carbon cycle in the east of China＇s seas has a high correlation with El Ni？o-Southern Oscillation（ENSO）.

Studies on the Community Structures of Meiofauna and Marine Nematode at Six Stations in the Southern Yellow Sea,China

Meiofauna (0.031-0.5 mm) were sampled and studied at a grid of six stationsduring the cruise of investigation for over winter ground of anchovy (Engraulis japonicus) in theSouthern Yellow Sea, China in January 2003. Total meiofauna individuals averaged (1.162 ± 0.347) x10^6 ind m^(-2) and the corresponding biomass 1.748 ± 0.72 g dwt m^(-2) with the maximum 2.35 g dwtm^(-2) at Station 9594 and the minimum 0.537 g dwt m^(-2) at Station 11794. A total of fourteentaxa were identified. Free living marine nematodes were the most dominant group with an averageabundance of (1.026 ± 0.206) x 10~6 ind m^(-2), accounting for 88.5% of total numbers, and anaverage of 85.4% lived in the surface layer (0-2cm) of sediments. The individual dry weight wascalculated, which ranges from 0.01 μg to 31.32 μg with an average of 0.261 μg. One hundred andforty two species or taxa of free-living marine nematodes belonging to 89 genera, 24 families and 4orders were identified. Six of them were new species. The common dominant species were Dorylaimopsisrabalaisi, Sphaerolaimus balticus, Sphaerolaimus mini-tus, Metalinhomoeus longicauda,Prochromadorella attenuata., Campylaimus sp. 1, Vasostoma sp. 1, Daptonema nor-mandicum,Paramonohystera riemanni, and Promonhystera sp. 1. According to cluster analysis of Primer 5.0, thesix stations were clustered into 2 groups with similar species composition at 40% similarity. Thespecies diversity index (H′), evenness index (J) and species richness index (d) of nematode werecalculated and analyzed. Correlation analysis with respect to environmental factors showed that theabundance of meiofauna had a significant correlation with the median diameter of sediment (Md_φ).The species richness of nematodes had a highly significant correlation with Chl-a and significantcorrelations with Pha-a and Chl-a + Pha-a.

A three-dimensional coupled physical-biological model study in the spring of 1993 in the Bohai Sea of China

A three-dimensional （3-D） coupled physical and biological model was used to investigate the physical processes and their influence on the ecosystem dynamics of the Bohai Sea of China. The physical processes include M2 tide, time - varying wind forcing and river discharge. Wind records from 1 to 31 May in 1993 were selected to force the model. The biological model is based on a simple, nitrate and phosphate limited, lower trophic food web system. The simulated results showed that variation of residual currents forced by M2 tide, fiver discharge and time-varying wind had great impact on the distribution of phytoplankton biomass in the Laizhou Bay. High phytoplankton biomass appeared in the upwelling region. Numerical experiments based on the barotropic model and baroclinic model with no wind and water discharge were also conducted. Differences in the results by the baroclinic model and the barotropic model were significant： more patches appeared in the baroclinic model comparing with the barotropic model. And in the baroclinic model, the subsurface maximum phytoplankton biomass patches formed in the stratified water.

Abnormality of the monsoon wind in the sea area along the southeasterncoast of China and the response of the northern areaof the South China Sea during the ENSO events

-Variations of monsoon wind field in the sea area along the southeastern coast of China during the ENSO events and its influence on the sea level and sea surface temperature (SST) are explored mainly on the basis of the data of monthly mean wind at 850 hPa and five coastal stations during 1973-1987. The results from the analyses of the data and theoretical estimation show that the southwest wind anomalies appeared in the study area during the events, and northeast wind anomalies occurred in general before the events. With the coastline of the area being parallel basically to the direction of the wind, an Ekman transport will result in an accumulation of the water near the coast or a departure of the water from the coast. As a result , the sea level and SST there will be affected markedly. During the events, southwest wind will intensify in the summer, and northeast wind will weaken in the winter. Their total effect is that a large negative anomaly of the sea level and SST will occur. The estimations indicate that the monsoon wind is stronger in the summer and weaker in the winter than the normal by 1-1. 5 m/s during the events, and this anomaly will cause a decrease of the sea level by 7-11 cm . Changes of the wind field, therefore, is mainly responsible for a large negative anomalies of the sea level and SST there during the ENSO events.

Sea level change along the coast of China relative to the isostatic datum

On the basis of the analyses of significant periods for the sea level observation data taken from recent several decades at 12 tide stations, the monthly mean sea level observations are fitted by a model of linear trend of sea level change superimposed with several variations of different fixed periods. The trends of sea level relative changes and their errors are estimated by the LS method. The results are reduced to the isostatic datum proposed and established in the paper (Huang et al. , 1991, Seismology and Geology , 1, 1-15). The trends of sea level changes in the near future along the coast of China are studied. It is pointed out that the general trend of the sea level change along the coast of China is going up slowly and the rate of the change is not the same in different segments of the coasts. In a few segments, the sea level is even relatively going down. The numerical results given in this paper provide a basis for the predictions of the future sea level changes and their effects.

Five New Records of Free-living Marine Nematodes in the Yellow Sea

Five species of free-living marine nematodes are redescribed and illustrated as new records in the Yellow Sea of China. These species include one monhysterid, Campylaimus gerlachi in the family Diplopeltidae and four enoplids species, Oxystomina elongata, Oxystomina elegans, Halalaimus lutarus and Halalaimus wodjanizkii in the family Oxystominidae. Ecological and taxonomic remarks are provided and discussed in comparison with the original description. The key to all known species of the genus Campylaimus is given. Our findings have offerred the taxonomic information of nematodes to the benthic ecology and biodiversity studies of the Yellow Sea.

Temporal and Spatial Distribution of DIN and DIP Concentrations and Source Apportionment Along the Bohai Sea of China During 2015-2022

The Bohai Sea is one of the most polluted sea areas in China.In this study,we used 2184 integrated concentrations of dissolved inorganic nitrogen(DIN)and dissolved inorganic phosphorus(DIP)in the Bohai Sea of China during spring(March,April,and May),summer(June,July,and August),and autumn(October and November)from 2015 to 2022 to explore the trends and sources of nutrients variations.From 2015 to 2022,DIN showed a downward trend until 2020 and then an upward trend,whereas DIP exhibited a stable trend with a slight decrease.The concentrations of DIN and DIP had similar seasonal pattern which was the highest in autumn(0.292±0.247 mg/L for DIN and 0.013±0.016 mg/L for DIP)but lower in spring(0.267±0.238 mg/L for DIN and 0.006±0.010 mg/L for DIP)and summer(0.263±0.324 mg/L for DIN and 0.008±0.010 mg/L for DIP).Sources of DIN and DIP apportioned by the positive matrix factorization(PMF)model were riverine input,sediment resuspension,sewage discharge,atmospheric deposition,and underground input.During 2015-2022,the largest contributor to DIN was sewage discharge(28.7%)and the largest contributor to DIP was sediment resuspension(44.6%).Seasonally,DIN in spring and autumn was dominated by sewage discharge(45.4%and 27.8%,re-spectively).Whereas in summer,it was dominated by riverine input(32.4%)and atmospheric deposition(29.7%).DIP was dominated by sediment resuspension during all three seasons(35.8%-52.5%).In addition,the increase in DIN concentrations in 2021 and 2022 were mainly due to the incremental input of river discharge and atmospheric deposition caused by increased precipitation during sum-mer and autumn.

Characteristics of the sea ice reflectance spectrum polluted by oil spills based on field experiments in the Bohai Sea

Oil spilled on the sea ice surface in the Bohai Sea of China is studied through the field measurements of the reflectance of a simulated sea ice-oil film mixed pixel. The reflection characteristics of sea ice and oil film are also analyzed. It is found that the mixed pixel of sea ice and oil film is a linear mixed pixel. The means of extracting sea ice pixels containing oil film is presented using a double-band ratio oil-film sea-ice index（DROSI） and a normalized difference oil-film sea-ice index（NDOSI） through the analysis of the reflectance curves of the sea iceoil film pixel for different ratios of oil film. The area proportion of the oil film in the sea ice-oil film pixel can be accurately estimated by the average reflectance of the band of 1 610–1 630 nm, and the volume of the spilled oil can be further estimated. The method of the sea ice-oil film pixel extraction and the models to estimate the proportion of oil film area in the sea ice-oil film pixel can be applied to the oil spill monitoring of the ice-covered area in the Bohai Sea using multispectral or hyperspectral remote sensing images in the shortwave infrared band（1 500–1 780 nm）.

Power of SAR Imagery and Machine Learning in Monitoring Ulva prolifera:A Case Study of Sentinel-1 and Random Forest

Automatically detecting Ulva prolifera(U.prolifera)in rainy and cloudy weather using remote sensing imagery has been a long-standing problem.Here,we address this challenge by combining high-resolution Synthetic Aperture Radar(SAR)imagery with the machine learning,and detect the U.prolifera of the South Yellow Sea of China(SYS)in 2021.The findings indicate that the Random Forest model can accurately and robustly detect U.prolifera,even in the presence of complex ocean backgrounds and speckle noise.Visual inspection confirmed that the method successfully identified the majority of pixels containing U.prolifera without misidentifying noise pixels or seawater pixels as U.prolifera.Additionally,the method demonstrated consistent performance across different im-ages,with an average Area Under Curve(AUC)of 0.930(+0.028).The analysis yielded an overall accuracy of over 96%,with an average Kappa coefficient of 0.941(+0.038).Compared to the traditional thresholding method,Random Forest model has a lower estimation error of 14.81%.Practical application indicates that this method can be used in the detection of unprecedented U.prolifera in 2021 to derive continuous spatiotemporal changes.This study provides a potential new method to detect U.prolifera and enhances our under-standing of macroalgal outbreaks in the marine environment.

Numeric modelling and risk assessment of pollutions in the Chinese Bohai Sea

To simulate the dynamic process of total nitrogen(TN) in seas, numerical modelling combined with the adjoint method is implemented in this study. Because nonpoint source terms(ST) and initial values(IV) of TN are essential but difficult to determine, the adjoint method was applied to a numerical model, and the ST and IV terms of TN were inverted via routine monitoring data in the Bohai Sea. In twin experiments, the adjoint method was capable of inverting the prescribed spatio-temporally distributed ST and the spatial distributed IV. In practical experiments, the results demonstrated that the simulation precision with ST inversion was higher than that with IV inversion and was accurate with joint initial values and source term(IST) inversion. This result indicates that nonpoint source TN is essential for the simulation of TN concentration. Furthermore, the simulated results indicate that the pollution in three bays of the Bohai Sea is rather severe. The model in this study is not specific to the Bohai Sea and can be generalized to other areas, such as the Beibu Gulf. These findings may assist in the development of cost-effective controls for accidental or planned industrial pollutant releases into coastal waters.