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Volume 40 ， Issue 2 ， 2022
- Abstract：To quantitatively investigate the water mass transport of mesoscale eddies, the mass transport induced by a simulated anticyclonic eddy in the South China Sea was evaluated by using the Regional Ocean Modelling System (ROMS) and a built-in passive tracer module. The results indicate that the eddy can trap and transport 51% of the initial water in the eddy core to 689 km from its origin during its lifetime of 100 days, with a stable loss rate of 6‰ per day. During propagation, there is drastic horizontal water exchange between the inside and outside of the eddy. Meanwhile, the vertical mass transport is significant, and 65% of the water initially in the mixed layer of the eddy is eventually detrained into the subsurface. A tracer budget analysis of eddy shows that advection is the dominant dynamic process of transport, while the effect of mixing is weak, and horizontal process plays a controlling role. Horizontal and vertical advection exhibit opposite patterns and strongly offset each other. Particularly, a distinct dipole pattern is found in the local velocity field of the eddy, with significant convergence (downwelling) and divergence (upwelling) zones in the anterior and posterior of the eddy, respectively, which is likely related to the driving mechanism of the westward propagation of the eddy. The dipole further induces a vertical overturning cell, through which the surface water in the anterior of the eddy detrains into the subsurface by downwelling and resurface from the posterior of the eddy by upwelling and gradually spreads out of the eddy. The temporal variability in the tracer budget is significant, in which horizontal advection is dominant. The propagation acceleration and temporal derivative of the deformation rate are highly correlated with tracer transport, suggesting the potential effect of the temporal instability of eddies on the eddy mass transport.Keywords：mesoscale eddy;mass transport;passive tracer;vertical velocity;mixing6|0|0Updated：2023-05-20
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The characteristics of spontaneous near-inertial wave generation from an anticyclonic mesoscale eddy
Abstract：The generation and propagation characteristics of near-inertial waves (NIWs) generated spontaneously from a quasi-geostrophic anticyclonic mesoscale eddy in a rotating and stratified fluid were investigated by three-dimensional numerical modeling. NIWs are generated over a long time interval as a forced response to balanced baroclinic mesoscale eddies. For such eddies, NIW generation from balanced flow is an inevitable result as the evolution of eddies. Moreover, the baroclinicity of mesoscale eddies is an essential condition for this NIW generation mechanism. The spontaneously generated NIWs radiate horizontally toward the eddy center and propagate upward in vertical direction. The forcing of the NIWs moves downward along the eddy axis from the location of maximum temperature anomaly of the mesoscale eddy. The moving speed of the forcing is independent on the balanced mesoscale eddies but is determined by the ratio of buoyancy to inertial frequency. When the forcing reaches the bottom of the mesoscale eddy, the spontaneous NIW generation process terminates. NIW intensity in this spontaneous generation process is strengthened with the increase of the Rossby and Froude numbers. Further research to gain a solid understanding of the role of the Rossby and Froude numbers is necessary for the parameterization of spontaneous NIW generation from quasi-geostrophic mesoscale eddies in general circulation model.Keywords：near-inertial waves (NIWs);anticyclonic mesoscale eddy;spontaneous generation7|0|0Updated：2023-05-20 - Abstract：The relative contributions of surface temperature and salinity to steric sea-level variations are investigated using satellite observations and reanalysis datasets. By defining a contribution factor, the relative roles of thermal and haline steric height variations are quantified over the South China Sea (SCS). The thermosteric height dominates the steric sea level variation in the northern SCS deep basin, while the contribution of the halosteric height increases southward. Further investigation reveals that this transition is related to the meridional imbalance of surface heat flux and precipitation variations. The revealed steric constitution distribution is not confined to the surface but extends within the upper layer to approximately 50m depth, and then the thermosteric component dominates from the depth underneath. The results of this study clarify the steric sea level constitution over the SCS, benefit the understanding of sea-level variations at the regional scale, and may further facilitate multisensor remote sensing data mining studies.Keywords：South China Sea (SCS);steric height;steric constitution10|0|0Updated：2023-05-20
- Abstract：Using the 25-h continuing hydrographic observations at three successive stations in February 2012 and the mooring time series of current observations from January to March 2015, the tidal currents and tidal energy fluxes in the coastal waters east of Hainan Island in the northwestern South China Sea were analyzed. The diurnal and semidiurnal (using K1 and M2 as proxies, respectively) tidal currents and associated isopycnal undulations were derived with harmonic analysis. Results show that the velocities of the diurnal and semidiurnal tides derived from the 25-h observations are comparable to those from the mooring series. The semi-major axes of the tidal ellipses were O(4–7 cm/s) for barotropic tides and O(2–4 cm/s) for baroclinic tides. The directions were in NE–SW at deeper stations to N–S at the shallowest station for the diurnal tide and from NW–SE to NE–SW for the semidiurnal tide. Both the diurnal and semidiurnal isopycnal fluctuations reached O(5 m), O(8 m), and O(10 m) at the cross-shelf stations (H03, H04, and H05) from 35 m, 45 m, to 55 m, respectively, showing insignificant vertical variation, and the barotropic signals were predominate. The baroclinic diurnal tide showed first-mode structures at H03-05, as does the semidiurnal tide at H03. The semidiurnal tide at H04 and H05 exhibited higher-mode structures. The time series of both the alongshore and cross-shore components reveal the vertically propagation features of the baroclinic tidal phase and energy. The calculated horizontal energy fluxes of the diurnal and semidiurnal internal tides decreased from O(0.1 W/m) at H05 to O(0.01 W/m) at H03, implying a propagation and dissipation of energy from offshore to inshore.Keywords：tidal current;Barotropic Tide;Internal Tide;energy flux;east of Hainan Island8|0|2Updated：2023-05-20
- Abstract：Features of oil spills and look-alikes in polarimetric synthetic aperture radar (SAR) images always play an important role in oil spill detection. Many oil spill detection algorithms have been implemented based on these features. Although environmental factors such as wind speed are important to distinguish oil spills and look-alikes, some oil spill detection algorithms do not consider the environmental factors. To distinguish oil spills and look-alikes more accurately based on environmental factors and image features, a new oil spill detection algorithm based on Dempster-Shafer evidence theory was proposed. The process of oil spill detection taking account of environmental factors was modeled using the subjective Bayesian model. The Faster-region convolutional neural networks (RCNN) model was used for oil spill detection based on the convolution features. The detection results of the two models were fused at decision level using Dempster-Shafer evidence theory. The establishment and test of the proposed algorithm were completed based on our oil spill and look-alike sample database that contains 1 798 image samples and environmental information records related to the image samples. The analysis and evaluation of the proposed algorithm shows a good ability to detect oil spills at a higher detection rate, with an identification rate greater than 75% and a false alarm rate lower than 19% from experiments. A total of 12 oil spill SAR images were collected for the validation and evaluation of the proposed algorithm. The evaluation result shows that the proposed algorithm has a good performance on detecting oil spills with an overall detection rate greater than 70%.Keywords：synthetic aperture radar (SAR) data;oil spill detection;subjective Bayesian;Faster-region convolutional neural networks (RCNN);Dempster-Shafer evidence theory6|0|0Updated：2023-05-20
- Abstract：Values for Doppler center frequency are calculated from the echo signal at the satellite using the Doppler centroid method and so include the predicted Doppler frequency caused by the relative motion of the satellite and the Earth, which is the main component of Doppler center frequency and must be removed to obtain the Doppler frequency anomaly for ocean current measurement. In this paper, a new Doppler frequency anomaly algorithm was proposed when measuring surface currents with synthetic aperture radar (SAR). The key of the proposed algorithm involved mean filtering method in the range direction and linear fitting in the azimuth direction to remove the radial and the azimuthal component of predicted Doppler frequency from the Doppler center frequency, respectively. The basis is that the theoretical Doppler center frequency model of SAR exhibits an approximately linear characteristic in both the range direction and in the azimuth direction. With the help of the new algorithm for predicted Doppler frequency removal, the estimation error of Doppler frequency anomaly can be reduced by avoiding employing the theoretical antenna pattern and imperfect satellite attitude parameters in the conventional Doppler frequency method. SAR measurement results demonstrated that, compared to the conventional Doppler frequency with/without error correction method, the proposed algorithm allows for a pronounced improvement in the current measuring accuracy in comparison with the global ocean multi-observation (MOB) products. In addition, the effectiveness and robustness of the proposed Doppler algorithm has been demonstrated by its application in the high velocity current in the Kuroshio region.Keywords：synthetic aperture radar (SAR);Doppler frequency;Doppler frequency anomaly;current retrieval;ocean surface currents8|0|0Updated：2023-05-20
- Abstract：Although four species of odontocete and four species of baleen whale have been recorded in Prydz Bay, their vocalizations have been rarely investigated. Underwater vocalizations were recorded during March 2017 in Prydz Bay, Antarctica. Bio-duck sounds, downsweeps, inverted "u" shape signals, whistles, pulsed sounds, and broadband clicks were recorded. Bio-duck sounds and downsweeps were associated with Antarctic minke whales (Balaenoptera bonaerensis) based on visual observations. Similarities between inverted "u" shape signals, biphonic calls, and clicks with vocalizations previously described for killer whales (Orcinus orca) lead us believe the presence of Antarctic killer whales. According to sound structures, signal characteristics, and recording location, Antarctic type C killer whales were the most probable candidates to produce these detected calls. These represent the first detection of inverted "u" shape signals in Antarctic waters, and the first report of Antarctic killer whale in Prydz Bay based on passive acoustic monitoring. The co-existence of Antarctic minke and killer whales may imply that minke whales can detect differences between the sounds of mammal-eating and fish-eating killer whales. Our descriptions of these underwater vocalizations contribute to the limited body of information regarding the distribution and acoustic behavior of cetaceans in Prydz Bay.Keywords：passive acoustic monitoring;inverted "u" shaped signal;killer whale;Antarctic minke whales;Prydz Bay;type C6|0|0Updated：2023-05-20
Physics
- Abstract：The Southwest Borneo (SW Borneo) block belongs to Sundaland and is the oldest continental fragment of Borneo that is believed to derive from the Gondwana land. The U-Pb isotopic dating ages of 113 detrital zircons from sandstones of the Ketapang Complex in SW Borneo range from 3 298 Ma to 78 Ma, and show six major age populations: 2 476-2 344 Ma, 2 016-1 831 Ma, 1 296-759 Ma, 455-406 Ma, 262-210 Ma, and 187-78 Ma. The youngest age of these detrital zircons is 78 Ma, indicating that the maximum depositional age of the sandstones is Campanian. Permian-Late Cretaceous detrital zircons are interpreted as having been derived from the nearby Schwaner Mountains and the Permian-Triassic tin belt granitoids in Southeast Asia (SE Asia). Archean-Carboniferous detrital zircons have a continental Gondwana provenance, with their age spectra similar to those of northwestern Australia, indicating that these zircons could be derived from the orogenic belts and cratons in northwestern and central Australia. The provenance of these detrital zircons in this study indicates the SW Borneo block was located on the northwestern margin of Australia during the Paleozoic, in the region of the Banda Embayment. SW Borneo rifted from Australia and moved northward in the Early Jurassic, and this block was added to Sundaland in the Early Cretaceous. The Luconia-Dangerous Grounds continental fragment derived from East Asia collided with SW Borneo after subduction in the Cretaceous, which induced the widespread magmatism in the Schwaner Mountains in SW Borneo.Keywords：detrital zircon;U-Pb dating;provenance;Southwest Borneo (SW Borneo);Sundaland10|0|1Updated：2023-05-20
Geology
- Abstract：The intrusion of the Kuroshio into the East China Sea (ECS) affects the development of hypoxia off the Changjiang (Yangtze) River estuary; however, quantitative analysis of its impacts is lacking. In this study, the Regional Ocean Modeling Systems (ROMS) model coupled with the Carbon, Silicate and Nitrogen Ecosystem (CoSiNE) model was used to investigate the relative importance of dissolved oxygen (DO) and different nutrients (silicate, nitrate, and phosphate) in the Kuroshio on hypoxia in the ECS. Results show that changes in DO concentrations in the Kuroshio modify the distribution and intensity of hypoxia through direct onshore transport by hydrodynamic processes. An increase in Kuroshio DO concentration by 25% or 50% would result in a decrease of the maximum hypoxia extent (MHE) in the ECS by 76% or 86%, respectively, while a 25% decrease in Kuroshio DO would increase the MHE by up to 219%. The contribution of DO in the Taiwan Strait is almost negligible. In contrast to Kuroshio DO, nutrients affect hypoxia in the ECS through onshore transport by hydrodynamic and biochemical processes. Changes in phosphate and nitrate concentrations by 25% in the Kuroshio would change the MHE by up to 30% and 18%, respectively, accompanied by apparent changes in surface chlorophyll-a concentrations. The effect of silicate on hypoxia is negligible because a 25% change in silicate concentrations in the Kuroshio would result in less than 1% change in the MHE. Our results reveal a hierarchical rank of importance for environmental variables in the Kuroshio (i.e., DO > phosphate > nitrate > silicate) in modifying the development of hypoxia in the ECS.Keywords：hypoxia;Kuroshio;Changjiang River estuary;East China Sea;dissolved oxygen;nutrient6|0|3Updated：2023-05-20
- Abstract：The Yellow Sea (YS) and East China Sea (ECS) are important marginal seas of the western Pacific. Understanding the dynamics of methane (CH4) in the YS and ECS are essential to evaluate the role of coastal seas in global warming. We measured dissolved CH4 at various depths in the water column of the YS and ECS during a cruise from March to April 2017. The concentrations of CH4 varied greatly in different water masses, suggesting that the hydrographic conditions can substantially affect the CH4 distribution. The CH4 budget in the shelf of the ECS, which was estimated with a box model, suggests CH4 consumption in the water column was the major sink (>95%), followed by a loss with a total of 2.2% CH4 released to the atmosphere. Overall a local CH4 production of 0.28 nmol/(L·d) was needed to maintain the CH4 excess. Results from laboratory incubations showed an increase in CH4 (1.5 times higher than the value of the control) after the addition of dimethylsulfoniopropionate (DMSP). Field incubations result in a CH4 production rate of 1.2 nmol/(L·d) under a N-stressed conditions (N: P<1), indicates that the DMSPdependent CH4 production prefer to occur in the oligotrophic seawaters, where nitrogen is depleted. This study demonstrates that the marginal seas of China is a hotspot for CH4 dynamics, and the cycling of methylated sulfur compounds (such as DMSP) may contribute importantly to locally formed CH4. This may have further implication to carbon and sulfur biogeochemical cycles in the western Pacific.Keywords：methane;East China Sea;Yellow Sea;aerobic production;dimethylsulfide (DMS);dimethylsulfoniopropionate (DMSP)6|0|1Updated：2023-05-20
- Abstract：The 22-year (1998-2019) surface seawater dimethylsulfide (DMS) concentrations in the Yellow Sea (YS) were hindcasted based on satellite sea surface temperature (SST) and chlorophyllα (Chlα) data using α generalized additive mixed model (GAMM). A continuous monthly dataset of DMS concentration in the YS was obtained after using the data interpolation empirical orthogonal function (DINEOF) to reconstruct missing information in the dataset. Then, the interannual DMS variability in the YS was analyzed. The results indicated that the monthly climatological DMS concentration in the YS was 3.61 nmol/L. DMS concentrations in the spring and summer were significantly higher than those in the autumn and winter. DMS concentrations were highest in coastal YS waters and lowest primarily in offshore YS waters. Interannual DMS variability between 1998 and 2019 was subdivided into two inverse phases: with the exception of the central YS, DMS increased before the turning point and decreased after. The turning point in interannual DMS variation was earlier in the inshore YS as compared to the central YS. Spectrum analysis identified some significant patterns of interannual variation in the DMS anomaly in the YS. Chl α appeared to be the main factor influencing interannual trends in DMS in the YS. Interannual DMS variability was under the joint control of Chl α and SST. However, short-term interannual DMS variation (2-3 years) was primarily related to SST, while longer term interannual DMS variation (6-8 years) was significantly correlated with Chl α and SST.Keywords：interannual variability;dimethylsulfide;hindcasting;generalized additive mixed modelling;Yellow Sea6|0|0Updated：2023-05-20
Chemistry
- Abstract：Dinoflagellates are the major causative agents of harmful algal blooms in the global ocean and they usually form blooms under conditions of very low dissolved inorganic phosphorus (DIP). However, the mechanisms underpinning the dinoflagellate blooms remain unclear. Here, we quantitatively compared protein expression profiles of a marine dinoflagellate, Prorocentrum donghaiense, grown in inorganic P-replete, P-deficient, and DIP- and dissolved organic phosphorus (DOP)-resupplied conditions by employing a Tandem Mass Tag (TMT)-based quantitative proteomic approach. Proteins involved in intracellular P reallocation, organic P, and non-P lipid utilization were up-regulated under the P-deficient condition, while inorganic phosphate transporters varied insignificantly. In response to the P resupplementation, nitrogen metabolism, ribosome, porphyrin, and chlorophyll metabolism were up-regulated, while lysosome, and starch and sucrose metabolism were down-regulated. Notably, photosynthesis was up-regulated and secondary metabolism was down-regulated only in the DIP-resupplied cells, whereas amino acid metabolism and vitamin B6 metabolism were up-regulated in the DOP-resupplied cells, indicating differential response mechanisms of P. donghaiense to DIP or DOP resupplementation. Our results indicated that P. donghaiense initiated multiple strategies in response to an ambient inorganic P-deficiency, and its efficient DOP assimilation by providing both P and carbon sources might be a key factor driving bloom formations of P. donghaiense in a low DIP environment.Keywords：marine dinoflagellates;harmful algal blooms;Prorocentrum donghaiense;phosphorus;quantitative proteomics6|0|0Updated：2023-05-20
Ecology
- Abstract：Phytoplankton are central components of marine environments, and are major players in the production and respiration budgeting. However, their diversity and distribution patterns are still poorly understood due largely to their small sizes and inconspicuous morphology that have been determined via the application of traditional morphology methods over the past two decades. To better understand the composition and diversity of phytoplankton in Jiaozhou Bay, China, seasonal sampling was carried out in 2019 and samples were analyzed with morphological observations and high-throughput sequencing, from which obvious seasonal variations in phytoplankton composition and proportional abundances were uncovered. Metabarcoding revealed far more diversity and species richness of phytoplankton than morphological observations, especially with respect to dinoflagellates. Diatoms were the most dominant phytoplankton group throughout the year, of which Thalassionema and Skeletonema were co-dominant in the bay. Parasitic dinoflagellates (e.g. Amoebophrya), which is often overlooked in the morphological observations, were in dominance and high diversity in the metabarcoding dataset, thus more attention should be paid to exploring the potential role of parasitic dinoflagellates. Temperature, chlorophyll a, and nutrient levels were the main influential factors on the distribution of phytoplankton. This study provided a comprehensive morphological and molecular description of phytoplankton and clearly demonstrated the importance of molecular technology in exploring phytoplankton communities. More-widespread use of molecular technology will facilitate deeper understanding of the ecological importance of the different species.Keywords：phytoplankton;high-throughput sequencing;diversity;morphological observation;Jiaozhou Bay6|0|1Updated：2023-05-20
- Abstract：Synechococcus is one of the most abundant picocyanobacteria in marine ecosystem,and the absence of Prochlorococcus would make it indispensable as a primary producer in the Bohai Sea,North China. However,the abundance distribution and genetic diversity of Synechococcus in this region have rarely been reported. In this study,the distribution pattern of Synechococcus abundance was investigated during four cruises in April,June,August,and November from 2018 to 2019, moreover,its phenogenetic diversity was studied based on high-throughput sequencing of the cpeBA operon. The results demonstrate that phycoerythrin-containing Synechococcus was most abundant in August when temperature was high and oxygen saturation was low. During this period,Synechococcus pigment type (PT) 2 was abundant in the Bohai Bay and Laizhou Bay under conditions of high nutrient concentration,temperature,and turbidity. In comparison,PT3,especially those clusters characterized with high or variable ratio of phycourobilin and phycoerythrobilin,was predominant in the Bohai Strait and Liaodong Bay under conditions of high salinity,pH,and oxygen saturation. Furthermore,co-occurrence correlations using network analysis revealed that Synechococcus PTs were related to 15.37%–43.48% of the prokaryotic genera. Synechococcus PT3c/PT3d and PT2 were the most important PTs in the network. The hierarchical clustering revealed that taxa co-occurred with Synechococcus PTs differed among samples. It could be attributed to the substance exchange and the environmental impact,which calls for more studies in the future.Keywords：Synechococcus;phenogenetic diversity;co-occurrence network;coastal ecosystem;Bohai Sea6|0|0Updated：2023-05-20
- Abstract：Although the microbial diversity of the Indian Ocean has been extensively investigated,little is known about the community composition of microbes in the Southern Indian Ocean. In the present study,we divided 60 water column samples on the Ninety-East Ridge (NER) into five water masses according to the temperature-salinity curves. We presented,for the first time,a full description of the microbial biodiversity on NER through high-throughput amplicon sequencing approach,including bacteria,archaea,and fungi. We found that bacteria exhibited higher richness and diversity than archaea and fungi across the water masses on NER. More importantly,each water mass on NER featured distinct prokaryotic microbial communities,as indicated by the results of non-metric multidimensional scaling. In contrast,fungi were eurybathic across the water masses. Redundancy analysis results demonstrated that environmental factors might play a pivotal role in the formation and stability of prokaryotic communities in each water mass,especially that of archaea. In addition,indicator species might be used as fingerprints to identify corresponding water masses on NER. These results provide new insights into the vertical distribution,structure,and diversity of microorganisms on NER from the perspective of water mass.Keywords：Ninety-East Ridge (NER);temperature-salinity curve;microbial vertical distribution;water mass;microbial diversity8|0|0Updated：2023-05-20
- Abstract：The hepatopancreas is an important tissue involved in various biological metabolism for mollusks,but its responses to ocean acidification (OA) have not been well evaluated. In this study,the oysters were cultured in simulated conditions by continuously bubbling with ambient air (pH=8.10) or air-CO2 (pH=7.50) for up to two months,and the variations on the antioxidant capacity,digestive ability,and microbiota composition in hepatopancreas of Crassostrea gigas were analyzed. The results show that although superoxide dismutase and glutathione responded quickly to OA stress,the antioxidant capacity of the hepatopancreas was inhibited,as revealed by the decrease of the total antioxidant capacity,which led to an upward trend of the malondialdehyde,demonstrating that the oxidative damages were accumulated under the OA process. The determination of the digestive ability manifested as the decrease of pepsin activity and the recovery of lipase and amylase activity after long-term acidification,which may be helpful to improve the adaptability of oysters. In addition,analysis on 16S rDNA amplicon revealed that the total species abundance and diversity of the hepatopancreas microbiota experienced a dynamic change,but finally it decreased greatly after long-term acidification. The structure of the hepatopancreas microbiota was changed drastically with the change of the dominant species from aerobic to the anaerobic and facultative anaerobic bacteria,and the abnormal proliferation of some species,such as genus of Mycoplasma and order Clostridiales,which may aggravate the adverse effects of OA on the physiological functions of the hepatopancreas. As a result,our findings enrich our understanding of the accumulated oxidative damage and adaptive digestive ability in oyster hepatopancreas caused by OA. For the first time,the changes of the hepatopancreas microbiota under long-term acidification conditions are described,proving a good reference for the study of the response and adaptation mechanisms of bivalve mollusks in a wide range of oceans OA.Keywords：ocean acidification;oyster;hepatopancreas;antioxidant defense;digestive enzymes;microbiota6|0|0Updated：2023-05-20
- Abstract：Fish otolith δ15N (δ15Noto) is a demonstrated source of information of dietary history for marine fish as it is available in otolith archives and sedimentary deposits unlike white muscle tissue (WMT). WMT and stomach content data are insufficient for trophic level (TL) data of past fishes which is important for the changes of marine fishery resources over long time scales. To determine the correlation between δ15Noto and fish WMT δ15N (δ15Nwmt) and the feasibility of using δ15Noto in characterizing the TLs of marine fishes,we conducted nitrogen stable isotope analysis (SIA) in the otolith and WMT of 36 marine fish species sampled from the Yellow Sea and northern East China Sea in 2011–2014. Both δ15Noto and δ15Nwmt were analyzed using an elemental analyzer coupled with an isotope ratio mass spectrometer (EA-IRMS). Multiple otoliths were combined to make each otolith measurement and were analyzed as-is without a carbonate dissolution pre-processing step. δ15Noto and δ15Nwmt comparisons for species in the Yellow Sea and northern East China Sea are currently lacking and would be helpful for both regional studies and for increasing the number of species for which δ15Noto and δ15Nwmt have been compared. Additionally,to determine the relative accuracy of trophic level calculated using δ15Noto,we compared TL calculated from δ15Noto to traditional trophic level metrics calculated using δ15Nwmt. The results showed a positive and highly significant correlation (R=0.780,P < 0.001) between δ15Noto and δ15Nwmt. Trophic level estimation using WMT (TLwmt) and otolith (TLoto) showed congruence in our study,which is not entirely surprising given that δ15Noto was regressed against δ15Nwmt and the resulting regression coefficient was used to convert δ15Noto to δ15Nwmt prior to calculating TLoto. This conversion was required in order to be consistent with previous δ15Nwmt-based calculations of TL for comparison. TLoto calculations resulted in TL values that were largely within 5%–10% of TL values calculated with δ15Nwmt. Our findings show that δ15Noto is a feasible technique for characterizing the TLs of marine fish and can also assist in food web and marine ecosystem studies.Keywords：stable isotope analysis;δ15N;otolith;trophic level6|0|1Updated：2023-05-20
- Abstract：Temperature is an important factor affecting the growth,development,and survival of organisms. The effects of temperature stress on aquatic organisms have received increasing attention,as these organisms are mostly poikilotherms and their body temperature are directly corresponding changes with ambient temperature,resulting in they are easily exposed in temperature stress. However,little is known about the effects of high temperature on Sipuncula. In this study,we investigated the effects of acute heat stress on malondialdehyde (MDA) concentration,the activities of antioxidant (superoxide dismutase and glutathione peroxidase) and immunity-related (acidic and alkaline phosphatase) enzymes,heat shock protein 70 (hsp70) and hsp90 gene expression,and the histological structure of the sipunculid Phascolosoma esculenta. Within the coelom fluid,the MDA concentration and all detected antioxidant enzyme activities increased during high temperature stress; significant increases were also observed here and in the intestine in the hsp70 and hsp90 mRNA expression levels. These results indicated that acute heat stress caused oxidative stress; antioxidants and heat shock proteins probably act to protect P. esculenta against oxidative damage,constituting part of its physiological mechanism for adaptation to high temperatures. In addition,the increased activity of the acidic and alkaline phosphatases indicated effects on its nonspecific immune system. Furthermore,damaged tissue structures were observed in the body wall,retractor muscle,intestine,and nephridium after 96 h of 40-℃ stress. The damaged cells of these tissues showed obvious condensed chromatin around the nuclear membrane. This histological damage suggests that heat stress could affect movement,food absorption,digestion,and excretion in P. esculenta. These results elucidate the effects of temperature stress on P. esculenta and its physiological response mechanisms and provide practical indicators for assessing heat stress status and determining suitable culture temperatures for P. esculenta.Keywords：heat stress;oxidation stress;enzyme activity;heat shock proteins;nonspecific immunity;histological damage6|0|0Updated：2023-05-20
Article
- Abstract：The chloroplast NADH dehydrogenase-like(NDH) complex, homologous to respiratory complex I, participates in photosystem I cyclic electron flow (PSI-CEF) and chlororespiration in photosynthesis. Phylogenetic analyses indicated that Zostera marina, a widely distributed seagrass, has a complete NDH complex, which is rarely observed in marine macrophytes. We identified all 31 ndh genes necessary for the functional NDH complex, of which ndhB and pnsb3 occurred as duplication events. Secondary structural analyses of antiporter-like subunits showed that the long amphipathic helix of NdhF was lost in Z. marina, which could exhibit an alternative mode in the generation of trans-thylakoid proton gradient. The splicing pattern of ndh exhibited tissue-specific patterns and responded to light stress. RNA editing in Z. marina presented the ancestral pattern with many of the primitive editing sites and types. The partial editing in ndhF reflected the link between light stress and RNA editing. Moreover, the predominant expression in leaves of most ndh genes suggested that their major function is in photosynthesis. The quantitative real time-PCR results show that the expression of ndh was significantly upregulated in response to light stress. Nevertheless, there were two diverse responsive mechanisms of the NDH complex in PSI-CEF and chlororespiration. Overall, the presence of a complete structure, upregulated gene expression level, and multiple post-transcriptional regulations could provide a molecular basis for the powerful NDH complex and enable Z. marina to maintain effective photosynthetic performance.Keywords：Zostera marina;NADH dehydrogenase-like complex;genome-wide analysis;profiles of expression6|0|0Updated：2023-05-20
- Abstract：Fifty protease-producing strains were screened from sediment of deep-sea cold seep, and divided into four different categories: Bacillus, Pseudoalteromonas, Vibrio, and Alteromonas according to the sequences of 16s rRNA. Their abilities to produce protease, amylase, and lipase were determined, and a Bacillus strain gcc-1 displayed very strong alkaline protease activity and stability under different thermal and acidic conditions. The purification of the protease produced by strain gcc-1 was carried out by precipitation with ammonium sulfate, and sequentially chromatographed by anion exchange column and gel filtration. The purified protease showed a single band at the molecular weight of 28 kDa by SDS-PAGE. The characterization results show that the purified protease exhibited a considerable activity and stability in a wide thermal range of 10-80℃ and a wide acidic range of pH 6.5-11.5, and displayed highest activity at 40℃ and pH 8.5. Notably, the protease still maintained high activity even at low to 10℃. Furthermore, the protease exhibited good stability in presence of different surfactants, organic solvents, oxidizing agent H2O2, and commercial detergents. Therefore, the protease produced by gcc-1 is a cold active and high stable enzyme, and has a promising potential in laundry detergent as an additive.Keywords：deep-sea;Bacillus;alkaline protease;purification;characterization6|0|0Updated：2023-05-20
- Abstract：An active photosystem (PS) Ⅱ particle and two light-harvesting complexes, as well as their sub-complexes that have not been reported previously, were isolated from a cryptophyte Chroomonas placoidea by Triton X-100 sucrose density gradient centrifugation. The fluorescence spectra revealed that there were efficient energy couplings between phycocyanin (PC645) and chlorophyll (Chl) within both zones Ⅲ and Ⅳ of the gradient, which were designated respectively as light-harvesting complex and PSⅡ particles whose size was 15-20 nm according to negative staining in electron microscopy. When the two complexes were further resolved into sub-complexes, the energy coupling was retained in the core PSⅡ complex (named as zone Ⅳ-2 of the sucrose gradient), which contained almost no outer antenna pigment Chl c. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) showed that the PC645 components appeared in Chl-containing protein complexes were mainly the β subunit with molecular weight of 20 kDa. These results demonstrate that PC645 in this cryptophyte was structurally but preferentially combined with the light-harvesting complex and PSⅡ core. The excitation energy absorbed by PC645 could be directly transferred to Chlα (especially the long wavelength of Chlα) in the PSⅡ reaction center or via the Chl α/c-protein complex. The β subunit corresponded to the terminal fluorescence emission and might play an important role in transmitting energy from PC645 to the Chl-protein complex. The results will help in elucidating the architecture and function of the energy transfer system comprising phycobiliproteins and Chl-protein complexes in cryptophytes.Keywords：Chroomonas placoidea;phycocyanin-chlorophyll-protein complex;photosystem Ⅱ;lightharvesting complex (LHC);phycocyanin (PC645);fluorescence spectra6|0|0Updated：2023-05-20
- Abstract：Three species of dinophysoid planktonic dinoflagellates are described from the eastern Mediterranean Sea. Amphisolenia sp. aff. brevicauda was collected at 70-m depth in the Ionian Sea. This small species showed a more asymmetric midbody and a proportionally longer neck when compared to the closer relative A. brevicauda. Three individuals of Dinofurcula tricornuta sp. nov. collected at 154-m depth in the Marmara Sea are characterized by three posterior-oriented processes when compared to its congeneric species. This is the first record of the genus Dinofurcula beyond the eastern tropical Pacific Ocean. Dinophysis profunda sp. nov. collected at 500-m depth in the Ionian Sea is characterized by ovate hypotheca and a serrate crest-like left sulcal list when compared to its close relative D. alata. These findings evidence an undescribed biodiversity in the under-sampled subphotic depths.Keywords：deep ocean;Dinophyta;Dinoflagellata;Mediterranean Sea;mesopelagic;new species6|0|0Updated：2023-05-20
- Abstract：Melosira is one of the most common diatom genera found in freshwater ecosystems. There are many freshwater species of Melosira, of which M. varians is the most common. In our investigation of periphytic diatoms in the Jinsha River, China, a new species, M. capsularum sp. nov, was characterized in combined morphological and molecular approaches. M. varians was also analyzed using molecular data. The new species is similar to M. varians, M. moniliformis, M. nummuloides, and M. lineata in morphology. The cells are capsular and join to filaments by mucilage pads that are secreted on the valve face and united into pairs by their cingula. The valve face is domed and covered with small granules, and the valve mantle edge has a milled appearance. The two strains of M. capsularum are in a single clade obviously away from other Melosira species, as determined in phylogenetic analysis based on nuclear small subunit (SSU) rDNA sequences and the chloroplast-encoded rbcL gene. Thus, the results of morphological comparisons and phylogenetic analysis based on molecular data provide strong evidence that M. capsularum is a new species, thereby increasing the total number of recognized freshwater diatom species in China. In addition, we have systematically reclassified the freshwater Melosira that have been recorded in China.Keywords：Melosira;morphology;molecular phylogeny;new species;revision6|0|2Updated：2023-05-20
- Abstract：The genus Sheathia consists of over 20 species primarily distributed in Asia, Europe, Oceania, North America, and Africa. However, the origin and evolution of this genus remain unclear. Two gametophyte stage specimens (SAS18052 and SAS18523) and two "Chantransia" stage specimens (YTS19161 and YTS19017) were collected from Shanxi and Henan Provinces in China, respectively. Based on morphological data, isolates YTS19161 and YTS19017 were similar to Audouinella pygmaea, whereas the morphological characteristics of SAS18052 and SAS18523 were in good agreement with the circumscription description of S. longipedicellata. Molecular sequences of rbcL, COI-5P, and psbA were used to investigate the phylogenetic, evolutionary, and biogeographic origin of the genus Sheathia. The three molecular markers supported that the two gametophyte stage specimens belong to S. longipedicellata, while the isolates YTS19161 and YTS19017 were the "Chantransia" of S. longipedicellata. Ancestral area reconstruction and divergence time estimation speculated that Sheathia originated in North America, a portion of the Pangaea at approximately 328.07-184.73 million years ago (Ma). Our relaxed molecular clock analysis suggests that the Florideophyceae diverged approximately 741.04 (894.36-631.70) Ma. The major divergences in this class involved the emergence of Nemaliophycidae[ca. 662.01 (779.83-580.51) Ma], and the split of orders Batrachospermales and Thoreales[ca. 456.10 (552.80-367.88) Ma].Keywords：divergence time;geographic origin;molecular analysis;morphology;phylogenetic relationship6|0|1Updated：2023-05-20
Biology
- Abstract：The kuruma shrimp Marsupenaeus japonicus is one of the most commercially important shrimp species in the world. Low salinity would affect the penetration and immunity, and even led to its death of the shrimp. However, little is known about the molecular mechanism of the effect. Therefore, hepatopancreas of M. japonicus reared under low-salinity stress for 6, 12, 24, 48, and 96 h was analyzed and the results were compared with that of the control group using transcriptomics. After removing reads containing adapters, 88 890 960-1 051 300 444 clean reads were generated from 10 libraries in the control group and experimental group. Compared with the control group, 811, 589, 1 095, 745, and 875 differentially expressed genes were obtained in the five treatment groups. The N50 and N90 lengths of the transcripts were 1 746 bp and 436 bp, respectively. The top 20 gene ontology terms and Kyoto Encyclopedia of Genes and Genomes pathways associated with the differentially expressed genes were related mainly to osmotic regulation (ion exchange, lipid metabolism and carbohydrate metabolism), immune regulation (cellular and humoral immunity), chitin metabolism, and related functions. The differential expression patterns of nine randomly selected genes were confirmed by quantitative real-time PCR. This is the first report of osmotic regulation-related genes that are differentially expressed under low-salinity stress in the hepatopancreas of M. japonicus. Furthermore, we found that M. japonicus initiated its own immune regulation under low-salinity stress. These results will help elucidating the mechanism of osmotic regulation and immune responses in this shrimp species.Keywords：Marsupenaeus japonicus;transcriptome;osmotic regulation;immune responses6|0|0Updated：2023-05-20
- Abstract：Chinese mitten crab, Eriocheir sinensis, is an economically important crab in China. Air exposure is a common stress for E. sinensis, especially during the harvest and transportation. Several studies have investigated the effects of air exposure stress on E. sinensis at physiological and molecular levels. However, the common and distinct mechanisms adopted by male and female crabs to cope with air exposure stress remain unclear. In this study, we performed a comparative transcriptome analysis from hepatopancreatic tissue of female and male Chinese mitten crabs in response to air exposure stress. In total, 428 and 1 322 differentially expressed genes (DEGs) were identified in female and male crabs under air exposure, respectively. Our results showed that the transcriptional levels of several glycolysis related genes and anti-apoptotic proteins were up-regulated in both female and male crabs in response to air exposure. Moreover, our findings indicated that female E. sinensis might preferentially increase the expression of heat shock proteins (HSPs) to deal with air exposure stress, while male E. sinensis tend to resist air exposure stress via increasing antioxidant enzyme expression. Overall, this study provides novel insights into the molecular mechanisms underlying the air exposure stress response of E. sinensis.Keywords：Eriocheir sinensis;air exposure;transcriptome;hepatopancreas6|0|0Updated：2023-05-20
- Abstract：The red swamp crayfish, Procambarus clarkii, is an economically important species especially in China. Their exoskeleton places serious constraints on growth and culture management. Their growth is achieved through intermittent molting/ecdysis. The longitudinal genetic dynamics for growth-related traits at different ecdysial points in P. clarkii has been unclear to date. In this study, conditional genetic analysis was carried out for growth-related traits (body weight, body length, chela length, and cephalothorax length) based upon a mixed genetic model with conditional additive, dominance, and genotype by environment effects in P. clarkii. A complete diallel cross was made among three geographic populations of P. clarkii for the genetic mating design. Results of the conditional genetic analysis showed that from 4th molt to 9th molt the conditional additive variations were increased significantly whereas the conditional non-additive genetic variations (dominance and genotype by environment interaction) were decreased significantly for these growth-related traits. This indicated that lots of new expression of additive effect genes for body weight, body length, chela length, and cephalothorax length occurred during ontogeny, and environment played a significant role in the expression of genes affecting these growth-related traits. Growth of the four traits was mainly affected by non-additive genetic effects in early developmental stage (prior to 4th molt). The cumulative conditional additive variation for the growth-related traits from 4th molt to 9th molt accounted for a large majority of the total conditional additive variations from 2nd molt to 9th molt, indicating that this period was very important for the growth of this species. Using the conditional analysis method, dynamics of growth-related traits during an important ontogenetic phase of red swamp crayfish was uncovered. Our results provide valuable insights into refining production of this species.Keywords：mating design;conditional genetic analysis model;Procambarus clarkii;genetic effect;conditional variance component;longitudinal genetic analysis6|0|0Updated：2023-05-20
- Abstract：Chemokines are cytokines that can promote the activation and migration of immune cells, and increase the recognition of antigen by antigen-presenting cells (APC). Previous studies showed that a DNA vaccine can induce humoral and cellular immune responses of flounder after immunization. To explore the improvement of chemokines on the efficiency of OmpK vaccine, two bicistronic DNA candidate vaccines were constructed and the immune responses they induced in the flounder were investigated by reverse transcription polymerase chain reaction (RT-PCR), indirect immunofluorescent assay (IFA), H & E staining, flow cytometry (FCM), and quantificational real-time polymerase chain reaction (qRT-PCR). pBudCE4.1 plasmid as an expression vector, bicistronic DNA vaccines encoding OmpK gene and CC-motif ligand 4 gene (p-OmpKCCL4), or Ompk gene and CC-motif ligand 19 gene (p-OmpK-CCL19) were successfully constructed. The results showed that two bicistronic DNA vaccines expressed Ompk protein of Vibrio anguillarum and CCL4/CCL19 proteins of flounder both in vitro and in vivo. After immunization, a large number of leucocytes in muscle were recruited at the injection site in treatment groups. The constructed vaccines induced significant increases in CD4-1+ and CD4-2+ T lymphocytes, and sIgM+ B lymphocytes in peripheral blood, spleen, and head kidney. The percentage of T lymphocytes peaked on the 14th post-vaccination day whereas that of B lymphocytes peaked in the 6th post-vaccination week. Moreover, the expression profiles of 10 immune-related genes increased in muscles around the injection site, spleen, and head kidney. After the challenge, p-OmpKCCL4 and p-OmpK-CCL19 conferred a relative percentage survival (RPS) of 74.1% and 63.3%, respectively, higher than p-OmpK alone (40.8%). In conclusion, both CCL4 and CCL19 can improve the protection of p-OmpK via evoking local immune response and then humoral and cellular immunity. CCL4 and CCL19 will be potential molecular adjuvants for use in DNA vaccines.Keywords：Vibrio anguillarum;outer membrane protein K;bicistronic DNA vaccines;CC-motif ligand 4;CC-motif ligand 19;immune response6|0|0Updated：2023-05-20
- Abstract：Using alternative plant-derived dietary protein to replace fishmeal, combined with practical evaluation indexes, is a recent focus for aquaculture practices. An 8-week feeding experiment with giant freshwater prawn Macrobrachium rosenbergii post-larvae was conducted to determine the effects of replacing fishmeal (FM) with soybean meal in the feed, in terms of growth performance, antioxidant capacity, intestinal microbiota, and mRNA expression of target of rapamycin (TOR) and ribosomal protein S6 kinase B1 (S6K1). Four isonitrogenous diets with isocaloric value were prepared to contain 100%, 75%, 50%, or 25% FM as the protein source (dietary treatments FM100, FM75, FM50, and FM25, respectively). Each diet was fed to post-larval prawns (mean weight 0.045±0.002 g) twice a day in four replicates. No significant difference in weight gain was observed among all groups, but the survival rate of prawns fed the FM50 and FM25 diets was significantly lower than that of prawns fed the FM diet. The mRNA expression of both TOR and S6K1 were the lowest in hepatopancreas of prawns fed the FM25 diet. Superoxide dismutase activity of prawns fed the FM25 diet was significantly lower than that of prawns fed FM50. In contrast, the malondialdehyde content was significantly higher in prawns fed FM25 as compared with those fed FM75. The proportion of fishmeal in the diet did not affect the composition of core (phylum-level) intestinal microbiota, but greater fishmeal replacement with soybean meal had a potential risk to increase the relative abundance of opportunistic pathogens in the gut when considered at the genus level. These results suggest that fishmeal replacement with soybean meal should not exceed 50% in a diet for post-larval M. rosenbergii.Keywords：animal protein;plant protein;replacement;protein synthesis;health;crustacean6|0|2Updated：2023-05-20
- Abstract：The small yellow croaker Larimichthys polyactis is a benthic marine fish species of high ecological and commercial importance and is widely distributed in the northwestern Pacific Ocean, especially in the Chinese coastal waters of the Bohai, Yellow, and East China Seas. As a highly migratory species, the whole life migration of L. polyactis has been intensively studied. However, knowledge about its early life migration is scarce, and population divisions are inconsistent, limiting the ability of fishery scientists and administrators to evaluate the design and potential benefits of thorough conservation and resource-management strategies. In the present study, otolith Sr/Ca was analyzed to investigate the early migratory patterns and discriminate the populations of L. polyactis in the Yellow Sea, including two spawning groups and one overwintering group. The variation in Sr/Ca ratios of ontogenetic growth zones, including the nucleus (N), larval (L), metamorphosis (M), juvenile (J), and edge (E) zones, was measured by electron probe microanalysis. The variation in Sr/Ca ratios in early developmental growth zones was generally characterized by an evident downward trend from the N to J zone, which suggests that the early migratory pattern of L. polyactis might be from inshore to nearshore water. Canonical discriminant analysis, based on the otolith Sr/Ca ratios of the N, L, M, and J zones, allowed the successful discrimination of the two populations, namely, the northern and southern Yellow Sea groups, whose differences were mainly reflected in the L and J zones. Compared with previous studies, the traditional geographic boundaries (34°N) separating these two populations might be moving northward. The application of otolith Sr/Ca ratios based on ontogenetic stage could improve our understanding of the migration and population discrimination of L. polyactis from the Yellow Sea.Keywords：otolith microchemistry;Larimichthys polyactis;early life migration;population discrimination;the Yellow Sea6|0|1Updated：2023-05-20
Aquaculture and Fisheries
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