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Volume 40 ， Issue 4 ， 2022
- Abstract：By incorporating the wave-induced Coriolis-Stokes forcing into the classical Ekman layer, the wave-modified ocean surface currents in the northwestern Pacific Ocean were estimated. Thus, the ocean surface currents are the combination of classical Ekman current from the cross-calibrated multi-platform (CCMP) wind speed, geostrophic current from the mean absolute dynamic topography (MADT), and waveinduced current based on the European Centre for Medium-Range Weather Forecasts (ECMWF) Interim Re-Analysis (ERA-Interim) surface wave datasets. Weight functions are introduced in the Ekman current formulation as well. Comparisons with in-situ data from Lagrangian drifters in the study area and Kuroshio Extension Observatory (KEO) observations at 32.3°N, 144.6°E, and 15-m depth indicate that wave-modified ocean surface currents provide accurate time means of zonal and meridional currents in the northwestern Pacific Ocean. Result shows that the wave-modified currents are quite consistent with the Lagrangian drifter observations for the period 1993-2017 in the deep ocean. The correlation (root mean square error, RMSE) is 0.96 (1.45 cm/s) for the zonal component and 0.90 (1.07 cm/s) for the meridional component. However, wavemodified currents underestimate the Lagrangian drifter velocity in strong current and some offshore regions, especially in the regions along the Japan coast and the southeastern Mindanao. What's more, the wavemodified currents overestimate the pure Eulerian KEO current which does not consider the impact of waves, and the zonal (meridional) correlation and RMSE are 0.95 (0.90) and 11.25 cm/s (12.05 cm/s) respectively. These comparisons demonstrate that our wave-modified ocean surface currents have high precision and can describe the real-world ocean in the northwestern Pacific Ocean accurately and intuitively, which can provide important routes to calculate ocean surface currents on large spatial scales.Keywords：ocean surface current;Ekman current;Geostrophic Current;Stokes drift6|0|0Updated：2023-05-20
- Abstract：Internal lee waves play an important role in transferring energy from eddies to small scale mixing. However, the energy conversion from eddies into lee waves in the global ocean remains poorly understood. Conversion rates from eddies and from mean flow in the global ocean were differentiated using single beam sounding data, stratification from climatology, eddy velocity, and mean flow from a global ocean model. The global integral energy conversion from eddies is estimated to be 0.083 TW and is almost twice as that from the mean flow. A new method was developed to study the uncertainties of energy conversion caused by dealing with the topographic data. Results show that different data processing procedures, and the resolution and accuracy of topographic data have a significant impact on the estimated global energy conversion.Keywords：internal lee waves;eddies;mean flow;energy conversion;topography6|0|0Updated：2023-05-20
- Abstract：Seamounts affect the surrounding physical oceanography and form unique dynamic processes. The influences of these processes on biological and sedimentary distributions are quite different in seamount areas at different depths. The Y3 seamount is located in the Yap Arc of the tropical Western Pacific Ocean. The water depth of its summit is ~280 m. Based on field data obtained in December 2014 and other openaccess data, the physical oceanography around the Y3 seamount was preliminarily analyzed. The results show that the upper layer (0-150 m) was under the influence of the westward-flowing North Equatorial Current (NEC), while the eastward-flowing North Equatorial Undercurrent (NEUC) controlled the water between 200-800 m. The NEC was strong and steady, but the NEUC was disturbed by the Y3 seamount. The cold dome above the Y3 seamount was not caused by a Taylor cap or tidal rectification but probably by upwelling during the survey time. Tidal currents were squeezed against topography and greatly amplified in the Y3 seamount. The thicknesses of the surface turbulent layers were greatly influenced by the springneap tidal cycle. The turbulent diffusivities in the sea surface layer above the Y3 seamount were much larger than those in the open ocean. Calculations showed that the surface wind stress greatly affected the turbulent mixing in the surface layer of the Y3 seamount. The reciprocal action between the amplified tidal currents and topography was the most likely cause of the turbulent mixing near the bottom of the Y3 seamount. This study can provide a scientific basis for further study of biological and depositional characteristics at the Y3 seamount.Keywords：Yap seamount;tropical Western Pacific Ocean;current;water mass;tides;turbulent diffusivity6|0|1Updated：2023-05-20
- Abstract：Ocean salinity is an essential measurable indicator of water cycle and plays a crucial role in regulating ocean and climate change. Using Simple Ocean Data Assimilation (SODA) reanalysis product, substantial decadal variability of the salinity in the upper layer of the South China Sea (SCS) from 1960 to 2010 was examined. Results show that a decadal variation of the upper layer salinity is clear. The upper layer (100 m) waters are found to freshen from 1960, become saltier during 1975 to 1995, and freshen again from 1995 to 2010. The strongest anomalies appear in the northeastern, northern, and northwestern regions in the three periods, respectively. The salinity variation trends become weaker below the upper layer, except the salinification trend in the northern SCS extends to at least 300 m during the salinification period. Diagnosis of the salinity budget over the top 100 m shows that during the first freshening period horizontal advection, vertical advection, and surface freshwater forcing all contribute to salinity freshening, and horizontal advection is relatively larger. The contribution of horizontal advection and surface freshwater forcing to the positive salinity anomaly is comparable, while the vertical advection is the secondary factor in the salinification period. Horizontal advection, especially zonal advection, plays a crucial role during the second freshening period. Moreover, horizontal advection is more important than that in the first freshening period. In addition, the contribution of horizontal advection is mainly in zonal direction controlled by Kuroshio intrusion. Further analysis shows the upper-layer salinity variations have a Pacific Decadal Oscillation (PDO)-like signal, with freshening during the negative PDO years, and salinification during the positive PDO years. PDO mainly influences the upper-layer salinity changes through both atmospheric bridge and oceanic bridge.Keywords：salinity;South China Sea (SCS);decadal variation;trend;salinity budget analysis6|0|0Updated：2023-05-20
- Abstract：Based on microstructure measurements from a repeated sampling station southwest of the Jeju Island during summer, we studied the hydrography, pycnocline turbulence, and vertical salt flux in the Changjiang Diluted Water (CDW). The water column was well stratified with the CDW occupied the surface ~20 m. Most of the large turbulent kinetic energy dissipation rate (ε) were found in the bottom boundary layer. Interestingly, intermittent strong turbulence (ε>10-6 W/kg) occurred in the pycnocline, which may induce strong mixing events and increase the vertical diffusive salt flux at the base of CDW by one order of magnitude. The daily-mean vertical diffusive salt flux could reach 4.3 (2.1, 8.9)×10-6 m/s. Both moored velocity measurements and associated wavelet analysis showed the presence of velocity fluctuations when there was strong pycnocline turbulence. The moderate resolution imaging spectroradiometer (MODIS) satellite images further suggest that the velocity fluctuations are induced by the prevailing internal solitary waves (ISWs) which are mainly generated at the shelf break of the East China Sea or the topographic features surrounding Jeju Island. The calculated gradient Richardson number denote the occurrence of shear instability in the pycnocline when strong turbulence presents. The presented results have strong implications for the importance of ISWs in influencing the vertical diffusion of CDW and changes in other properties.Keywords：turbulence;vertical salt flux;internal solitary wave;Changjiang River plume10|0|2Updated：2023-05-20
- Abstract：Synthetic Aperture Radar (SAR) plays a major role in identifying oil spills on the sea surface. However, obtaining information of oil spill thickness (volume) is still a challenge. Emulsification is an important process affecting the thickness and normalized radar cross section (NRCS) of oil film. Experiments of crude oil emulsification with C-band fully-polarized scatterometer were conducted combining airborne hyperspectral imaging spectrometer and 3D laser scanner observation data, to provide experimental parameters and method to support accurate remote sensing monitoring on marine oil spill. It is further proved that through quantitative homogeneous emulsified oil spill experiments, to a certain extent, the NRCS of oil film increased during the emulsification process of crude oil. The backscattering mechanism of crude oil emulsification was explored using a semi-empirical model (SEM); the change of oil film NRCS was modulated by its dielectric constant and surface roughness, in which the dielectric constant showed a dominant effect. The relationship between thickness and NRCS of oil film was studied under two experimental conditions. The differences of NRCS between oil film and adjacent seawater (Δσ0) and the damping ratio (DR) were found to have a linear relationship with oil thickness, which were best in the vertical polarization mode (VV) at 45° incident angle during the quantitative crude oil homogeneous emulsification process. In the natural emulsification process of continuous oil spill in which oil film was mixed with both crude oil and emulsified oil, an empirical equation of oil film thickness is preliminarily established. The Δσ0, DR, and the empirical equation of oil film thickness were applied to the marine continuous oil spill incident on a 19-3 oil platform with spaceborne SAR image and successfully explained the distribution of the relative thickness of the oil film.Keywords：crude oil emulsification;normalized radar cross section (NRCS);moisture content;oil film thickness;damping ratio15|0|1Updated：2023-05-20
Physics
- Abstract：The Chaoshan depression, a Mesozoic basin in the Dongsha sea area, northern South China Sea, is characterized by well-preserved Mesozoic strata, being good conditions for oil-gas preservation, promising good prospects for oil-gas exploration. However, breakthrough in oil-gas exploration in the Mesozoic strata has not been achieved due to less seismic surveys. New long-offset seismic data were processed that acquired with dense grid with single source and single cable. In addition, the data were processed with 3D imaging method and finer processing was performed to highlight the target strata. Combining the new imaging result and other geological information, we conducted integrated interpretation and proposed an exploratory well A-1-1 for potential hydrocarbon. The result provides a reliable basis for achieving breakthroughs in oil and gas exploration in the Mesozoic strata in the northern South China Sea.Keywords：Chaoshan depression;Mesozoic strata;oil and gas exploration;long offset seismic data;integrated interpretation;exploratory well6|0|1Updated：2023-05-20
- Abstract：Carbonate samples were collected from the northern Okinawa Trough in the East China Sea in 2013. The petrology, mineralogy, carbon and oxygen isotopes, and rare earth elements (REEs) of these samples were analyzed. Aragonite, high-Mg calcite, and dolomite were the main carbonate minerals, the contents of which varied greatly among the carbonate samples. Petrological observations revealed the common occurrence of framboidal pyrites. The δ13C values of carbonates varied from -53.7‰ to -39.3‰ (average of -47.3‰ based on Vienna Pee Dee Belemnite (V-PDB), n=9), and the δ18O values ranged from 0.6‰ to 3.4‰ (average of 1.9‰; V-PDB, n=9). The carbon and oxygen isotope characteristics indicated that the carbonates precipitated during the anaerobic oxidation of methane. The carbon source was a mixture of thermogenic methane and biogenic methane, possibly with a greater contribution from the former. The oxygen isotope data showed that gas hydrate dissociation occurred during carbonate precipitation. The Ce anomalies suggested that the carbonates precipitated in an anoxic environment. A slight enrichment of middle REEs (MREEs) could be attributable to the early diagenesis. The structures, minerals, oxygen isotopes, and MREEs all indicated that the carbonates experienced some degree of early diagenesis. Therefore, the influence of early diagenesis should be considered when using geological and geochemical proxies to reconstruct original methane seepage environments.Keywords：authigenic carbonate;carbon and oxygen isotopes;rare earth elements (REEs);anaerobic oxidation of methane (AOM);northern Okinawa Trough6|0|0Updated：2023-05-20
- Abstract：Poyang Lake in the Changjiang (Yangtze) River catchment has undergone frequent spring drought since 2003, and some researchers attributed this phenomenon to sand mining and the lakebed deformation in the outlet channel linking the lake with Changjiang River main channel. However, there is still a lack of high-resolution subaqueous geomorphological evidence of how sand mining led to lakebed deformation in the outlet channel. We examined the bed morphology and sub-bottom sedimentary structure of the outlet channel, using a multibeam echo sounder and sub-bottom profiler in Poyang Lake. We found that: (1) the subaqueous micro-topography types of the outlet channel are characterized by sand mining disturbance, natural erosional topography, and flat bed and dunes, accounting for 44.9%, 21.4%, 28.6%, and 5.1% of the channel area, respectively; and (2) sand mining activity affects the local bed topography extensively and significantly. The depth of sandpits caused by sand mining varied from 1.4 m to 12 m deeper than the surrounding bed surface, with 4.41 m of depth increase on average. Hence, the large-scale high-intensity sand mining activities and their significant geomorphic effects demand for an improved assessment for future management and longer-term sustainability. Because of the large-scale and ongoing high-intensity sand mining activities in the Poyang Lake outlet channel, these effects should raise caution in the future and contribute to monitoring efforts that are essential to implement sustainable management solutions. The present study and techniques implemented can serve as a scientific reference for dam construction and sand mining within the Poyang Lake basin.Keywords：lakebed deformation;sand mining;multibeam echo sounder;Poyang Lake6|0|1Updated：2023-05-20
Geology
- Abstract：The ocean could profoundly modulate the ever-increasing atmospheric CO2 by air-sea CO2 exchange process, which is also able to cause significant changes of physical and biogeochemical properties in return. In this study, we assessed the long-term average and spatial-temporal variability of global air-sea CO2 exchange flux (FCO2) since 1980s basing on the results of 18 Coupled Model Intercomparison Project Phase 6 (CMIP6) Earth System Models (ESMs). Our findings indicate that the CMIP6 ESMs simulated global CO2 sink in recent three decades ranges from 1.80 to 2.24 Pg C/a, which is coincidence with the results of cotemporaneous observations. What's more, the CMIP6 ESMs consistently show that the global oceanic CO2 sink has gradually intensified since 1980s as well as the observations. This study confirms the simulated FCO2 could reach agreements with the observations in the aspect of primary climatological characteristics, however, the simulation skills of CIMP6 ESMs in diverse open-sea biomes are unevenness. None of the 18 CMIP6 ESMs could reproduce the observed FCO2 increasement in the central-eastern tropical Pacific and the midlatitude Southern Ocean. Deficiencies of some CMIP6 ESMs in reproducing the atmospheric pressure systems of the Southern Hemisphere and the El Niño-Southern Oscillation (ENSO) mode of the tropical Pacific are probably the major causes.Keywords：air-sea CO2 flux;Coupled Model Intercomparison Project Phase 6 (CMIP6);Earth System Model (ESM);long-term average;spatial-temporal variability8|0|1Updated：2023-05-20
- Abstract：Being an exclusive construction material for lightweight rail vehicles, protection from pitting corrosion in harsh marine atmospheric environment in high humidity and Cl– ion concentration is critical for austenitic SUS 301L stainless steel (SS), especially when it inevitably suffers from mechanical damages during post disposals. Herein, an innovative dry passivation method for austenitic SUS 301L SS was established in a closed air atmosphere at low temperature and constant pressure. The process parameters were optimized, and the passivation mechanism was explained using polarization curve, electrochemical impedance spectroscopy (EIS), X-ray photoelectron spectroscopy (XPS), and contact angle measurement. The pitting corrosion susceptibility of the passive film prepared in a closed air chamber under 1.0×105 Pa at 80 ℃ for 80 min was evaluated in 3.5% NaCl solution and exhibited higher pitting potential and corrosion resistance, lower passivity-maintaining current density, and wettability when compared with conventional nitric acid treatment. Besides, dry passivation facilitated the repairing of the surface structural defect itself and the post-processing damage, similar to the accelerated aging of film. The decrease in oxygen concentration and convection-diffusion strengthened the preferential chromium oxidation to form a compact chromium-rich passive film to resist the aggression of Cl– ion.Keywords：austenitic stainless steel;passive film;dry passivation;pitting corrosion;chloride ion6|0|1Updated：2023-05-20
- Abstract：Nitrate addition is a common bio-competitive exclusion (BCE) method to mitigate corrosion in produced water reinjection systems, which can affect microbial community compositions, especially nitrate and sulfate reducing bacteria, but its effectiveness is in controversy. We investigated the influence of nitrate concentrations on EH40 steel corrosion affected by coexistence of Desulfovibrio vulgaris and Pseudomonas aeruginosa bacteria. Results demonstrate that only mixed bacteria or nitrate had little effect on EH40 steel corrosion, and nitrate could accelerate the corrosion of EH40 steel through the action of microorganisms. The corrosion promotion of nitrate was dependent on its concentrations, which increased from 0 to 5 g/L and decreased from 5 to 50 g/L. These differences were believed to be related to the regulation of nitrate in the growth of bacteria and biofilms. Therefore, care must be taken to BCE method with nitrate when nitrate reducing bacteria with high corrosive activity are present in the environments.Keywords：microbiologically influenced corrosion;nitrate;Desulfovibrio vulgaris;Pseudomonas aeruginosa6|0|2Updated：2023-05-20
- Abstract：In order to explore the interactional relations of internal chloride and external chloride-binding amongst the cementitious materials, the chloride-binding capacity of mortars composed of marine sand (MS) or washed marine sand (WMS) were investigated. Results indicate that more external chloride can penetrate and diffuse more deeply into the WMS mortar than that in the MS mortar. This phenomenon suggests that the external chloride migration resistance due to WMS is lower than that caused by MS. The distribution trends of the bound chloride content in the two types of mortars are the same at different immersion times. However, a significantly decreased area of the bound chloride content exists at the border of the external penetration area (EPA) and the external unaffected area (EUA) at the immersion ages of 3 and 7 d, and then it disappears gradually with immersion time. The WMS mortar can bind more external chloride, whereas the MS mortar can bind more internal chloride, at different immersion times. The distributions of bound chloride conversion rate in the EPAs of the two types of mortars differ across immersion times. The distribution firstly decreases, and then it increases at the immersion ages of 3 and 7 d. The distribution was from increase, then decreases, and increase again at the immersion ages of 28 and 56 d. The bound chloride conversion rate in the WMS mortar is affected more greatly by external chloride penetration than that in the MS mortar. The amounts of the Friedel's salt tend to increase with prolonged immersion time. Finally, the penetration of external chloride can increase the amount of fine capillary pores smaller than 100 nm in the WMSmortar exposed for 56 d in the chloride salt solution (WMS-E) specimen.Keywords：marine sand;mortar;chloride binding;Friedel's salt;pore structure6|0|0Updated：2023-05-20
Chemistry
- Abstract：Reservoirs are an important water source in many densely populated areas in southwest China. Phytoplankton play an essential role in maintaining the structure and function of reservoir ecosystems. Understanding the succession in phytoplankton communities and the factors driving it are essential for effective water quality management in drinking water reservoirs. In this study, water samples were collected monthly at the surface layers from March 2016 to December 2019 in Hongfeng Reservoir, southwest China. The relationship between functional group succession was analyzed based on nonmetric multidimensional scaling analysis (NMDS), redundancy analysis (RDA), succession rate, and other analysis methods. The results showed distinct shifts in the community structure of phytoplankton functional groups within study period. The Cyclotella sp. was dominant in 2016 and 2017, and Pseudanabaena limnetica was the dominant group in 2018 and 2019. It appears that the phytoplankton composition and biomass are closely related to the water temperature and nutrient status in this reservoir. The results clearly showed that the permanganate index (CODMn) was the key factor of dramatic phytoplankton functional group succession, and the change in succession rates was closely caused by total nitrogen concentration (TN). Therefore, the succession pattern and key factors of Hongfeng Reservoir revealed in this study were important guidance for the management of drinking water reservoirs in southwest China. A reasonable limit on exogenous nutrient input should be a priority, especially in high water temperature period.Keywords：phytoplankton functional groups;driving factors;nonmetric multidimensional scaling;succession rates;redundancy analysis6|0|2Updated：2023-05-20
Ecology
- Abstract：Relationship between biodiversity and ecosystem function is one of the core issues in ecological research. Phytoplankton, as the main producer of aquatic ecosystem, its diversity, productivity, and community stability are of great significance to reveal ecosystem function. There are significant differences in hydrodynamics, water retention time, and phytoplankton community structure between river-type reservoir and newly built lake-type reservoir. The comparative analysis of phytoplankton community stability between the two types of reservoir has not been reported. Jiuquwan Reservoir (river-type) and Taihu Reservoir (laketype), the two reservoirs in the Dongjiang River source area of Zhujiang (Pearl) River Basin, were selected for comparison in terms of multi-year operation vs. new impoundment, river-type vs. lake-type, and shallow water vs. sub-deep water reservoirs. Samples were collected in dry season (December 2019), normal season (March 2020), and wet season (August 2020), on which the phytoplankton diversity and productivity of the two reservoirs, and the relationship and difference of community stability were examined. Results show that (1) the number of phytoplankton species in Jiuquwan Reservoir decreased comparing that before algal bloom and the restoration treatment, while that in Taihu Reservoir increased compared with that before the impoundment of the reservoir. There was no significant difference in functional groups and species number between the two reservoirs (P>0.05); (2) the biological stability, diversity, productivity, and resource utilization efficiency of newly built lake-type reservoir were higher than those of multi-year river-type reservoir. In addition, the utilization efficiency of phytoplankton resources was the highest in wet season in both reservoirs. The increases in biodiversity, richness, and evenness promoted the stability of the community, while increases in productivity and resource utilization efficiency weakened the stability of the community; (3) community stability was affected by both biotic and abiotic factors, and hydrodynamic index was the main factor. This study is helpful to understand the relationship and differences in phytoplankton diversity, productivity and community stability in different types of reservoirs, and provides a guidance for maintaining the stability of reservoir water ecosystem and protecting the biodiversity. The relationships between phytoplankton diversity, productivity, and community stability will be investigated in depth, for which a long-term observation will be conducted on the impact of environmental factors and diversity on the local biostability in different types of reservoirs.Keywords：community stability;functional group stability;phytoplankton diversity;resource utilization efficiency;reservoir6|0|0Updated：2023-05-20
- Abstract：Microorganisms play a key role in aquatic ecosystems. Recent studies show that keystone taxa in microbial community could change the community structure and function. However, most previous studies focus on abundant taxa but neglected low abundant ones. To clarify the seasonal variation of bacterial and microalgal communities and understand their synergistic adaptation to different environmental factors, we studied the bacterial and eukaryotic phytoplankton communities in Fenhe River that runs through Taiyuan City, central China, and their seasonal co-occurrence patterns using 16S and 18S rDNA sequencing. Results indicate that positive interaction of eukaryotic phytoplankton network was more active than negative one except winter, indicating that the cooperation (symbiotic phenomenon in which phytoplankton are interdependent and mutually beneficial) among them could improve the adaption of microbial community to the local environmental changes and maintain the stability of microbial network. The main genera that identified as keystone taxa in bacterial network were Salinivibrio and Sphingopyxis of Proteobacteria and they could respond to the variation of nitrite and make use of it, while those that identified as keystone taxa in eukaryotic phytoplankton network were Pseudoschroederia and Nannochloris, and they were more susceptible to nitrate and phosphate. Mychonastes and Cryptomonas were closely related to water temperature. However, the loss of the co-occurrence by environmental factor changes affected the stability of network structure. This study provided a reference for analyzing relationship between bacteria and eukaryotic phytoplankton and revealing potential importance of keystone taxa in similar ecological domains in carbon, nitrogen, and phosphorus dynamics.Keywords：seasonal co-occurrence;bacteria and eukaryotic phytoplankton communities;keystone taxa;ecological effect;urban aquatic ecosystem6|0|0Updated：2023-05-20
- Abstract：Bacteria communities in cnidarian jellyfish can be harmful to many important aquaculture species, as they can be key vectors of bacterial pathogens. However, our knowledge of bacterial communities associated with jellyfish in culture ponds and their potential roles in the regulation of aquaculture species remains unclear. In this study, sequencing based on the bacterial 16S rRNA gene was used to investigate the composition and variation of the bacterial communities associated with hydromedusa Gonionemus vertens in sea cucumber culture ponds and natural marine environment. The associated bacterial communities of G. vertens from the culture ponds in the Yellow Sea and Bohai Sea had significantly different compositions, when compared with those from ambient seawater environment. Furthermore, bacterial communities associated with G. vertens had similar diversity and composition in culture ponds and natural marine environment in the Yellow Sea. There were 31 unique bacterial biomarkers identified in three locations. The major communities were highly abundant in Kiloniellales, Octadecabacter, Polynucleobacter, and Polaribacter, and are related to the environmental information processing. Pathogen candidates such as Vibrionales and Chlamydiales had notably low relative abundances (< 1%). The venom of the jellyfish was considered responsible for damage to the aquaculture. This study provides important data to help assess the impact of cnidarians-associated bacterial communities on pond aquaculture and the influences on material cycling and energy flow in marine ecosystems.Keywords：bacterial community;hydromedusa;the Yellow Sea;the Bohai Sea7|0|0Updated：2023-05-20
- Abstract：Climate change can affect fish individuals or schools, and consequently the fisheries. Studying future changes of fish distribution and abundance helps the scientific management of fisheries. The dynamic bioclimate envelope model (DBEM) was used to identify the "environmental preference profiles" of the studied species based on outputs from three Earth system models (ESMs). Changes in ocean conditions in climate change scenarios could be transformed by the model into those in relative abundance and distribution of species. Therefore, the distributional response of 17 demersal fishes to climate change in the Yellow Sea could be projected from 1970 to 2060. Indices of latitudinal centroid (LC) and mean temperature of relative abundance (MTRA) were used to represent the results conducted by model. Results present that 17 demersal fish species in the Yellow Sea show a trend of anti-poleward shift under both low-emission scenario (RCP 2.6) and high-emission scenario (RCP 8.5) from 1970 to 2060, with the projected average LC in three ESMs shifting at a rate of -1.17±4.55 and -2.76±3.82 km/decade, respectively, which is contrary to the previous projecting studies of fishes suggesting that fishes tend to move toward higher latitudes under increased temperature scenarios. The Yellow Sea Cold Water Mass could be the major driver resulting in the shift, which shows a potential significance to fishery resources management and marine conservation, and provides a new perspective in fish migration under climate change.Keywords：climate change;dynamic bioclimate envelope model;distribution shifts;relative abundance;Demersal Fish;Yellow Sea6|0|0Updated：2023-05-20
- Abstract：Over the last decades, the species distribution model (SDM) has become an essential tool for studying the potential effects of climate change on species distribution. In this study, an ensemble SDM was developed to predict the changes in species distribution of swimming crab Portunus trituberculatus across different seasons in the future (2050s and 2100s) under the climate scenarios of Representative Concentration Pathway (RCP)4.5 and RCP8.5. Results of the ensemble SDM indicate that the distribution of this species will move northward and exhibit evident seasonal variations. Among the four seasons, the suitable habitat for this species will be significantly reduced in summer, with loss rates ranging from 45.23% (RCP4.5) to 88.26% (RCP.8.5) by the 2100s. The loss of habitat will mostly occur in the East China Sea and the southern part of the Yellow Sea, while a slight increase in habitat will occur in the northern part of the Bohai Sea. These findings provide an information forecast for this species in the future. Such forecast will be helpful in improving fishery management under climate change.Keywords：Portunus trituberculatus;climate change;species distribution model;suitable habitat6|0|1Updated：2023-05-20
- Abstract：Antarctic krill is the key species of ecological system in the Amundsen Sea. At present, the suitable distribution is unobtainable by scientific surveys or data from the fishery. In this paper, the maximum entropy algorithm (Maxent) was used to obtain the potential distribution of adult Antarctic krill in order to provide useful information and reasonable reference for the policy on protecting potential krill habitats around the Amundsen Sea. Occurrence points and 17 environmental variables were used to simulate the distributions. Results show that the high and moderate suitable habitats lie between 65°S and 72°S in the Amundsen Sea. The high suitable habitat accounts for 8.1% of the total area of the Amundsen Sea. The sea ice persistence (ICE), total phytoplankton (PHYC), and the minimum value of dissolved iron (Fe_min) are the three dominant contributors to the model. Results from the response curves show that Antarctic krill preferred habitats with ICE of 0.42-0.93, PHYC of 2.48-2.77 mmol/m3 and Fe_min of (7.10×10-5)-(9.45×10-5) mmol/m3. Positive trends existed in the PHYC of the high and moderate suitable habitat, and a positive trend existed in the Fe_min of moderate suitable habitat. However, the probability of presence of Antarctic krill will decrease if the increase of the PHYC and Fe_min continues.Keywords：krill;Amundsen Sea;Maxent;potential distribution7|0|1Updated：2023-05-20
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Diverse habitat preferences of two sea cucumber species and the seasonal change in a coral reef area
Abstract：Different sea cucumbers have different preferred habitats and seasonal changes, which is still lack of detailed research. This study selects two common tropical sea cucumbers (Holothuria edulis and Stichopus chloronotus) to explore the reasons that affect their habitat selection and seasonal changes, so as to provide support for the spatial planning of sea cucumbers reserve in coral reef area. The study area is a compound distribution area of living coral reefs and sandy bottom in the north of Wuzhizhou Island. The survey time is January, April-September, 2019. Three fixed transects (G, H, and Q) were selected to reveal the population ecological characteristics of them in the typical dry season (January, April, May, and June) and rainy season (July, August, and September). The variation range of density for H. edulis and S. chloronotus were 2.0-8.9 inds./10 m2 and 0.2-0.7 inds./10 m2, respectively. The population density in rainy season was significantly higher than that in dry season (P < 0.05). H. edulis tends to be distributed in deeper water. The distribution of H. edulis was significant positively correlated with the sand coverage and sand continuity in G transect (P < 0.05), and significant negatively correlated with live coral coverage in three transects (P < 0.01). The shift from dry season to rainy season is a key factor affecting their habitat preference. In dry season, the preferred habitats of S. chloronotus are small rock (SR), sand (S), and small coral reef (SCR), while the H. edulis is S, SR, and dead coral rubbles (DCR). In rainy season, the preferred habitats of S. chloronotus are shift to SCR and SR, while the H. edulis is SCR, DCR, and sand.Keywords：habitat preference;coral reef;population density;Holothuria edulis;Stichopus chloronotus6|0|0Updated：2023-05-20 - Abstract：Radionuclides accidentally released from nuclear power plants, such as 137Cs and 60Co, can lead to severe contamination of marine ecosystems. Living macroalgae are efficient in absorbing metal elements from seawater. A 10-day simulation was conducted to assess the potential of scavenging cesium (Cs) and cobalt (Co) with live Ulva prolifera that was cultured in seawater medium containing Cs and Co in different concentrations (0 (the control), 10, 20, 50, and 100 mg/L). In the experiment, 5 kg (fresh weight) of U. prolifera was cultured in natural seawater in 90-L tanks. Results showed that after the experiment, the average bioconcentration factors (BCFs) of the control group were 247.2 and 1 126.4 for Cs and Co, respectively. The absolute absorption quantity of U. prolifera increased and the BCFs decreased with the increase in Cs and Co concentrations. The biosorption of the two metals on the first day well fit the pseudosecond-order equation (R2>0.95), indicating that adsorption is the rate-limiting step in the total biosorption process. Concentrations of both metal ions declined significantly in the first hour and decreased by 25.2% and 15.5% in 48 h, respectively. Therefore, live U. prolifera is efficient at scavenging Cs and Co in seawater, providing potential applications for the phytoremediation of radionuclides contaminated seawaters.Keywords：radionuclide pollution;phytoremediation;green tide;Ulva prolifera;biosorption kinetics7|0|0Updated：2023-05-20
Continued from the back cover
- Abstract：The most prominent biological characteristic of Porphyridium purpureum is their unique extracellular sulfated polysaccharides that plays an important protective role against salt stress. Adaptation to stress is associated with metabolic adjustments. However, the molecular mechanisms underlying such metabolic changes remain elusive. This study presents the first transcriptome profiling of P. purpureum. A total of 8 019 assembled transcripts were identified, annotated, and classified into different biological categories and pathways based on a BLAST analysis against various databases. The in-depth analysis revealed that many of the differentially expressed genes in P. purpureum under salinities of 68 and 0 involved polysaccharide metabolism. A comparison of the gene expression levels under different salinities revealed that the polysaccharide synthetic pathway was significantly upregulated under the 68 salinity condition. The increased expression of the FBP, pfkA, CS, pgm, USP, UGP2, galE, and MPI transcripts in the polysaccharide synthetic pathway and the increase in ATP2 and ATP6 transcripts in the energy metabolic pathway revealed the molecular mechanism of high-salt adaptation. This sequencing dataset and analysis could serve as a valuable resource to study the mechanisms involved in abiotic stress tolerance in Rhodophyta.Keywords：transcriptome;salinity;polysaccharides;osmotic adjustment;enzyme activity6|0|0Updated：2023-05-20
- Abstract：To investigate the effect of reduced salinity on diatoms' capacity to cope with changing ultraviolet radiation (UVR) and photosynthetically active radiation (PAR), Skeletonema costatum was grown in a range of salinity (15, 25, and 35). The photosystem II (PSII) function was analyzed by increasing PAR and UVR to mimic a mixing event in turbulent waters. The results show that high UVR exposure significantly reduced PSII activity, especially in cells grown at low salinity. UVR, but not salinity, stimulated the nremovalo rate of PSII protein PsbA. Salinity alone, in the range of 15 to 35, did not regulate PSII acceptor region; however, the low salinity+UVR treatment decreased the energy flux for electron transport per PSII reaction center in S. costatum. It showed that low salinity exacerbated the damaging effect of UVR on PSII function in S. costatum by suppressing PsbA protein synthesis and modifying the photochemistry of PSII. Although higher catalase (CAT) activity and NPQs were induced, they were unable to prevent the combined damage effect of low salinity+UVR. Our findings indicate that reduced salinity and increased UVR potentially affect the abundance and distribution of S. costatum with the escalation of climate disturbances.Keywords：diatom;ultraviolet radiation (UVR);photoinactivation;photosystem II8|0|1Updated：2023-05-20
- Abstract：As an important pattern recognition receptor (PRR) in the innate immune system, C-type lectin plays an important role in the innate immune process of invertebrates. Two C-type lectins SpCTL-C and SpCTL-D were characterized from mud crab (Scylla paramamosain). The predicted SpCTL-C and SpCTL-D proteins both contain a single carbohydrate-recognition domain (CRD) with key motif GlnPro-Ala (QPA) and Met-Pro-Ala (MPA), respectively. SpCTL-C and SpCTL-D transcripts distributed in all examined tissues, and the expression level was the highest in hepatopancreas. As PRR, the purified recombinant proteins rSpCTL-C and rSpCTL-D have high affinity for three kinds of pathogen-associated molecular patterns (PAMPs): β-glucan, lipopolysaccharide, and peptidoglycan. Besides, rSpCTL-D can bind to all nine microorganisms tested, while rSpCTL-C can bind to seven microorganisms except for Staphylococcus aureus and Micrococcus luteus. Both rSpCTL-C and rSpCTL-D showed agglutination activity towards fungi Pichia pastoris and Saccharomyces cerevisiae. However, rSpCTL-C and rSpCTL-D exhibited different antimicrobial activities: rSpCTL-D has a certain inhibitory effect on the growth of Vibrio fluvialis and M. luteus, while rSpCTL-C has no obvious inhibitory activity. The results show that rSpCTL-C and rSpCTL-D had better phagocytosis-promoting effect on M. luteus than the negative control. Meanwhile, both rSpCTL-C and rSpCTL-D had certain encapsulation-promoting activity. Collectively, two C-type lectins with novel key motifs make an important impact as PRR in immune response towards pathogens. At the same time, they play different functions in the innate immunity of mud crab S. paramamosain.Keywords：Scylla paramamosain;immune response;innate immunity;C-type lectin6|0|0Updated：2023-05-20
- Abstract：Cavefish can be important models for understanding the relationships among evolution, adaptation, and development in extreme environments. However, cavefish remain poorly studied, particularly at the genome level. Here, we sequenced the complete mitogenome of three cavefish in the family Nemacheilidae (Paranemachilus pingguoensis, Oreonectes polystigmus, and Heminoemacheilus longibarbatus), which were collected from karst caves in South China. The mitogenomes each contained 37 genes (13 protein coding, 22 tRNA, and two rRNA genes) and a single control region, with the same genetic arrangement and distribution as those found in vertebrates. The non-synonymous/synonymous mutation ratios (Ka/Ks) of the mitogenomes indicated that the protein-coding genes (PCGs) of the three cavefish evolved under purifying selection. The mitogenomes of the three cavefish exhibit nucleotide composition biases for PCGs, tRNAs, rRNAs, and the whole genome, indicating that the mitochondrial DNA might have been subjected to evolutionary selection in response to extreme cave environments. Divergence time and evolutionary history analyses suggested that the speciation and diversification of the cavefish coincided with the Miocene uplift of the southern Qinghai-Tibet Plateau, which greatly changed cave habitats. Overall, our study sheds light on the mitogenomes, phylogeny, and evolutionary history of nemacheilid cavefish.Keywords：cavefish;mitochondrial genome;evolution;Nemacheilidae6|0|0Updated：2023-05-20
- Abstract：Two species of Leodamas (Annelida, Orbiniidae) from China seas are described based on both material of the Marine Biological Museum (Chinese Academy of Sciences, Qingdao), and newly collected specimens. Leodamas robustus sp. n. is characterized by having uncini arranged in two short rows, anterior row with 3-5 uncini, increasing in size, with uncini on posterior chaetigers thicker, heavier and more curved than those on precedent chaetigers; posterior row with 2-5 uncini, thin and delicate, nearly the same size on all chaetigers, with 2-3 thin capillaries dorsally to two rows of uncini. Leodamas weizhouensis sp. n. is characterized by having delicate pocket-like membrane below and posterior to neuropodia, neuropodia of thoracic chaetigers with five dense rows of uncini. A key to all species of Leodamas from China seas is also provided.Keywords：Beibu Gulf;East China Sea;Polychaeta;South China Sea;taxonomy6|0|1Updated：2023-05-20
Biology
- Abstract：Ridgetail white prawn Exopalaemon carinicauda is an important economic marine species in China. To improve the germplasm quality of cultured E. carinicauda, for the first time, we estimated the heritability of ammonia tolerance and survival of E. carinicauda, covering 263 full-sib families in multiple generations. Analysis models including binary linear animal model (BLA), binary linear sire-dam model (BLSD), probit threshold animal model (PTA), and probit threshold sire-dam model (PTSD) were used. The estimated heritability of tolerance to ammonia in different models ranged from 0.09 to 0.22, and that of survival rate ranged from 0.06 to 0.16. Concerning the tolerance to ammonia, both the PTSD and BLSD models showed comparatively better prediction accuracies (0.48 and 0.47, respectively) than PTA and BLA models (0.40 and 0.26, respectively), while to the survival rate, all four models presented relatively low predictive abilities (0.16-0.26). This study provided important information for the future breeding program of E. carinicauda.Keywords：heritability;Exopalaemon carinicauda;tolerance to ammonia;survival rate6|0|1Updated：2023-05-20
- Abstract：Biofloc technology (BFT) improves water quality, and productivity of the farmed species through converting ammonium nitrogen to microbial protein, stabilizing microbial community, and reducing the production cost. In this study, a small-scale biofloc development unit was designed in combination of recirculation system (RAS) for Artemia culture. Artemia growth, water quality, and microbial composition of bioflocs in RAS were studied in comparison with in-situ batch culture (Glu). Glucose was added in RAS and Glu at C/N ratio of 10. The cultures without glucose addition, but with 50% daily water renewal (WRe) and without water renewal (NWRe) were considered as the controls. Artemia were cultured at 25 ¦ and salinity 30 for 24 days and fed formulated feed. The results showed that compared to the controls, Glu significantly improved the Artemia biomass, increased the biofloc volume, and reduced the content of total ammonia nitrogen (TAN), nitrite nitrogen (NO2-N) and nitrate nitrogen (NO3-N) in water column (P < 0.05). In addition, RAS had similar results with Glu. High throughput sequencing analysis on biofloc microbial composition demonstrated that glucose supplement shaped the microbial community structure, and increased proportion of potential probiotic bacteria and suppressed pathogenic bacteria growth. Furthermore, we analyzed the relationship between the microbial composition of biofloc and environmental factors. Canonical correspondence analysis (CCA) indicated that inorganic nitrogen in culture water had great impact on biofloc microbial composition in NWRe and WRe, whilst the dissolved organic carbon (DOC) modified the microbial community in Glu and RAS. This study shows the advantages of BFT in Artemia culture and provides practical information for applying BFT-RAS in indoor Artemia culture.Keywords：biofloc technology;Artemia;water quality;microbial community structure6|0|0Updated：2023-05-20
- Abstract：The set-net fishery resources in Haizhou Bay, China have been over-exploited because of overfishing and environmental deterioration. To better understand the current situations and the development trends of fishery resources, the temporal change of biological characteristics and community compositions were analyzed from 2011 to 2018. Meanwhile, we evaluated the impact of the summer moratorium of marine fishing (SMMF) on the set-net fishery. Results show that the mean total length of the six principal species showed varying degrees of decreasing trends, while the changing patterns for the mean weight proportion of the six groups varied. For the whole communities, the similarities of the inter-annual community diversities and compositions were high. SMMF is meaningful to help reproductive success and support recruitment. Every year, the catch per unit efforts of the six principal species after SMMF were significantly higher than before SMMF except for Octopus ocellatus. The target groups showed a higher mean weight proportion after SMMF than before SMMF in eight years, while the non-target groups were converse. Therefore, the resources of the set-net fishery are changing in the study periods; and SMMF is an important factor influencing biological characteristics and community structure. Despite some challenges, SMMF is still one of the most appropriate policy tools to protect the set-net fishery resources under the reality of China.Keywords：small-scale fishery;biological characteristics;species groups;community structure;seasonal closure11|0|0Updated：2023-05-20
Aquaculture and Fisheries
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