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Volume 41 ， Issue 1 ， 2023
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Effect of compressive strength on the performance of the NEMO-LIM model in Arctic Sea ice simulation
Abstract：Satellite records show that the extent and thickness of sea ice in the Arctic Ocean have significantly decreased since the early 1970s. The prediction of sea ice is highly important, but accurate simulation of sea ice variations remains highly challenging. For improving model performance, sensitivity experiments were conducted using the coupled ocean and sea ice model (NEMO-LIM), and the simulation results were compared against satellite observations. Moreover, the contribution ratios of dynamic and thermodynamic processes to sea ice variations were analyzed. The results show that the performance of the model in reconstructing the spatial distribution of Arctic sea ice is highly sensitive to ice strength decay constant (Crhg). By reducing the Crhg constant, the sea ice compressive strength increases, leading to improved simulated sea ice states. The contribution of thermodynamic processes to sea ice melting was reduced due to less deformation and fracture of sea ice with increased compressive strength. Meanwhile, dynamic processes constrained more sea ice to the central Arctic Ocean and contributed to the increases in ice concentration, reducing the simulation bias in the central Arctic Ocean in summer. The root mean square error (RMSE) between modeled and the CryoSat-2/SMOS satellite observed ice thickness was reduced in the compressive strength-enhanced model solution. The ice thickness, especially of multiyear thick ice, was also reduced and matched with the satellite observation better in the freezing season. These provide an essential foundation on exploring the response of the marine ecosystem and biogeochemical cycling to sea ice changes.Keywords：sea ice;compressive strength;sensitivity experiment;ocean-sea ice model;Arctic Ocean17|0|2Updated：2023-04-27 - Abstract：The upper mixed layer depth (h) has a significant seasonal variation in the real ocean and the low-order statistics of Langmuir turbulence are dramatically influenced by the upper mixed layer depth. To explore the influence of the upper mixed layer depth on Langmuir turbulence under the condition of the wind and wave equilibrium, the changes of Langmuir turbulence characteristics with the idealized variation of the upper mixed layer depth from very shallow (h=5 m) to deep enough (h=40 m) are studied using a non-hydrostatic large eddy simulation model. The simulation results show that there is a direct entrainment depth induced by Langmuir turbulence (hLT) within the thermocline. The normalized depthaveraged vertical velocity variance is smaller and larger than the downwind velocity variance for the ratio of the upper mixed layer to a direct entrainment depth induced by Langmuir turbulence h/hLT < 1 and h/hLT> 1, respectively, indicating that turbulence characteristics have the essential change (i.e., depth-averaged vertical velocity variance (DAVV) < depth-averaged downwind velocity variance (DADV) for shear turbulence and DAVV>DADV for Langmuir turbulence) between h/hLT < 1 and h/hLT>1. The rate of change of the normalized depth-averaged low-order statistics for h/hLT < 1 is much larger than that for h/hLT>1. The reason is that the downward pressure perturbation induced by Langmuir cells is strongly inhibited by the upward reactive force of the strong stratified thermocline for h/hLT < 1 and the effect of upward reactive force on the downward pressure perturbation becomes weak for h/hLT>1. Hence, the upper mixed layer depth has significant influences on Langmuir turbulence characteristics.Keywords：the upper mixed layer depth;Langmuir turbulence;turbulent characteristics;large eddy simulation6|3|1Updated：2023-04-27
- Abstract：Estuarine projects can change local topography and influence water transport and saltwater intrusion. The Changjiang (Yangtze) River estuary is a multichannel estuary, and four major reclamation projects have been implemented in the Changjiang River estuary in recent years: the Xincun Shoal reclamation project (RP-XCS), the Qingcao Shoal reclamation project (RP-QCS), the Eastern Hengsha Shoal reclamation project (RP-EHS), and the Nanhui Shoal reclamation project (RP-NHS). The effects of the four reclamation projects and each project on the saltwater intrusion and water resources in the Changjiang River estuary were simulated in a 3D numerical model. Results show that for a multichannel estuary, local reclamation projects change the local topography and water diversion ratio (WDR) between channels and influence water and salt transport and freshwater utilization in the estuary. During spring tide, under the cumulative effect of the four reclamation projects, the salinity decreases by approximately 0.5 in the upper reaches of the North Branch and increases by 0.5–1.0 in the middle and lower reaches of the North Branch. In the North Channel, the salinity decreases by approximately 0.5. In the North Passage, the salinity increases by 0.5–1.0. In the South Passage, the salinity increases by approximately 0.5 in the upper reaches and decreases by 0.2–0.5 on the north side of the middle and lower reaches. During neap tide, the cumulative effects of the four reclamation projects and the individual projects are similar to those during spring tide, but there are some differences. The effects of an individual reclamation project on WDR and saltwater intrusion during spring and neap tides are simulated and analyzed in detail. The cumulative effect of the four reclamation projects favors freshwater usage in the Changjiang River estuary.Keywords：reclamation projects;saltwater intrusion;freshwater resources;numerical model;Changjiang River estuary8|1|0Updated：2023-04-27
- Abstract：It is essential to acquire sound speed profiles (SSPs) in high-precision spatiotemporal resolution for undersea acoustic activities. However, conventional observation methods cannot obtain high-resolution SSPs. Besides, SSPs are complex and changeable in time and space, especially in coastal areas. We proposed a new space-time multigrid three-dimensional variational method with weak constraint term (referred to as STC-MG3DVar) to construct high-precision spatiotemporal resolution SSPs in coastal areas, in which sound velocity is defined as the analytical variable, and the Chen-Millero sound velocity empirical formula is introduced as a weak constraint term into the cost function of the STC-MG3DVar. The spatiotemporal correlation of sound velocity observations is taken into account in the STC-MG3DVar method, and the multi-scale information of sound velocity observations from long waves to short waves can be successively extracted. The weak constraint term can optimize sound velocity by the physical relationship between sound velocity and temperature-salinity to obtain more reasonable and accurate SSPs. To verify the accuracy of the STC-MG3DVar, SSPs observations and CTD observations (temperature observations, salinity observations) are obtained from field experiments in the northern coastal area of the Shandong Peninsula. The average root mean square error (RMSE) of the STC-MG3DVar-constructed SSPs is 0.132 m/s, and the STC-MG3DVar method can improve the SSPs construction accuracy over the space-time multigrid 3DVar without weak constraint term (ST-MG3DVar) by 10.14% and over the spatial multigrid 3DVar with weak constraint term (SC-MG3DVar) by 44.19%. With the advantage of the constraint term and the spatiotemporal correlation information, the proposed STC-MG3DVar method works better than the ST-MG3DVar and the SC-MG3DVar in constructing high-precision spatiotemporal resolution SSPs.Keywords：space-time multigrid 3DVar;sound speed profiles;temperature;salinity;spatiotemporal correlation;multiscale6|0|0Updated：2023-04-27
Physics
- Abstract：Compression is required for all kinds of subduction initiations, which may cause either subsidence or uplift, depending on the ages of the oceanic plates. Subduction initiations associated with the old oceanic crust tend to amplify preexisting subsidence by compression, whereas those associated with young oceanic plates may result in uplift.Keywords：subduction initiation;induced and spontaneous;west Pacific;plate tectonics5|0|0Updated：2023-04-27
- Abstract：The circum-Pacific convergent margin is known as "the Ring of Fire", with abundant volcano eruptions. Large eruptions are rare but very disastrous. It remains obscure how are large explosive volcanos formed and where are the danger zones. Three largest eruptions since 1900, the Hunga Tonga-Hunga Ha'apai, the Mt. Pinatubo, and the Novarupta were found to be associated with subductions of volatile-rich sediments and located close to slab windows. Among them, the Hunga Tonga-Hunga Ha'apai is close to subducting seamount chains; the Mt. Pinatubo is right next to subducting fossil ridges. Both seamount chains and fossil ridges have water depths much shallower than the carbonate compensation depths (CCD) in the Pacific Ocean. Seismic image shows that a seamount is subducting towards the Novarupta volcano. Subduction of volatile-rich sediments and a slab window nearby are the two most important favorable conditions for catastrophic eruptions. Slab windows expose the mantle wedge to the hot asthenosphere, which increases the temperature and dramatically promotes the partial melting of the carbonate-fluxed domains, forming volatile-rich magmas that powered explosive eruptions.Keywords：large explosive volcanos;subducting seamount chains;volatile-rich sediments;slab windows;Tonga5|0|0Updated：2023-04-27
- Abstract：Deep-water coarse-grained channels are embedded within a polygonal fault tier, and the polygonal faults (PFs) present non-polygonal geometries rather than classic polygonal geometry in plan view. However, PFs present differences when they encounter deep-water (coarse-grained vs. fine-grained) channels with different lithology, which has not been further studied to date. Three-dimensional (3D) seismic data and a drilling well from Beijiao sag of Qiongdongnan basin, South China Sea were utilized to document the plan view and cross-sectional properties of the PFs and their differences and genetic mechanism were investigated. Results show that, first, PFs can be divided morphologically into channel-segmenting PFs and channel-bounding PFs in plan view. The former virtually cuts or segments the axes of channels in high- and low-amplitudes, and the latter nearly parallels the boundaries of the channels. Both are approximately perpendicular to each other. Secondly, channel-bounding PFs that related to low-amplitude channels are much longer than those of high-amplitude ones; channel-segmenting PFs related to low-amplitude channels are slightly longer than the counterparts related to high-amplitude channels. Lastly, the magnitudes (e.g., heights) of the PFs are proportional to the scales (e.g., widths and heights) of low-amplitude channels, whereas the magnitudes of the PFs are inversely proportional to the scales of high amplitude channels. Coarse-grained (high amplitude) channels act as a mechanical barrier to the propagation of PFs, whereas fine-grained (low-amplitude) channels are beneficial to the propagation and nucleation of PFs. Additionally, the genetic mechanism of PFs is discussed and reckoned as combined geneses of gravitational spreading and overpressure hydrofracture. The differences of the PFs can be used to reasonably differentiate coarse-grained channels from fine-grained channels. This study provides new insights into understanding the different geometries of the PFs related to coarse-grained and fine-grained channels and their genetic mechanism.Keywords：polygonal faults;coarse-grained channels;fine-grained channels;gravitational spreading;overpressure hydrofracture4|0|0Updated：2023-04-27
- Abstract：The long-distance movement of turbidity currents in submarine canyons can transport large amounts of sediment to deep-sea plains. Previous studies show obvious differences in the turbidity current velocities derived from the multiple cables damage events ranging from 5.9 to 28.0 m/s and those of field observations between 0.15 and 7.2 m/s. Therefore, questions remain regarding whether a turbid fluid in an undersea environment can flow through a submarine canyon for a long distance at a high speed. A new model based on weakly stable sediment is proposed (proposed failure propagation model for weakly stable sediments, WSS-PFP model for short) to explain the high-speed and long-range motion of turbidity currents in submarine canyons through the combination of laboratory tests and numerical analogs. The model is based on two mechanisms: 1) the original turbidity current triggers the destabilization of the weakly stable sediment bed and promotes the destabilization and transport of the soft sediment in the downstream direction and 2) the excitation wave that forms when the original turbidity current moves into the canyon leads to the destabilization and transport of the weakly stable sediment in the downstream direction. The proposed model will provide dynamic process interpretation for the study of deep-sea deposition, pollutant transport, and optical cable damage.Keywords：turbidity current;excitation wave;dense basal layer;velocity;WSS-PFP model4|0|1Updated：2023-04-27
Geology
- Abstract：The composition and concentration of dissolved free amino acid (DFAA) of seawater samples collected in May 2016 from the surface to the hadal zone of the northern region of the Yap Trench were analyzed by pre-column derivatization of o-phthalaldehyde. Results show that the average concentration of DFAA in the study area was 0.47±0.36 μmol/L. In different sampling stations, the concentrations of DFAA with water depth showed complex variation patterns. At the sediment-seawater interface, the concentrations of DFAA in the western side of the trench were obviously higher than that in its eastern side. In the study area, there were no significant correlations between the concentrations of DFAA and the environmental parameters such as concentrations of chlorophyll a (Chl a), dissolved oxygen (DO), pH, and dissolved inorganic nitrogen (DIN), indicating that the concentrations of DFAA in seawater of the trench are affected by many factors, such as photosynthesis, respiration, temperature, pressure, illumination, and circulation. The dominant DFAA are similar in different water layers of sampling stations, including aspartic acid (Asp), glutamic acid (Glu), glycine (Gly), and serine (Ser). The composition of different amino acids, and the relative abundance of acidic, basic, and neutral amino acids might be related to the sources and consumption of various amino acids. Nine pairs of amino acids in the DFAA showed significantly positive relationship by correlation matrix analysis, suggesting that they might share similar biogeochemical processes. The degradation index (DI) of the DFAA in seawater of the Yap Trench could reflect the degradation, source, and freshness of DFAA in the trench to some extents. This is a preliminary study of amino acids from sea surface to hadal zone in the ocean, more works shall be done in different trenches to reveal their biogeochemical characteristics in extreme marine environments.Keywords：dissolved free amino acid (DFAA);Yap Trench;"Jiaolong" submersible;abyss;hadal zone;degradation Index (DI)7|0|0Updated：2023-04-27
- Abstract：Microbial communities, sulfur isotope of sulfides (δ34SAVS and δ34SCRS), and sulfur and oxygen isotopes of sulfate (δ34SSO4 and δ18OSO4) in sediments were analyzed to reveal the biogeochemical transformations of sulfur in a seabird-affected lake Y2 and a seabird-free YO from Fildes Peninsula, Antarctic Peninsula. The microbial communities in Y2 were mainly associated with penguin activities, while those in YO were limited by nutrients. The much enriched δ34SSO4 recorded at depth of 30, 41, and 52 cm in Y2 indicates very strong sulfate reduction therein. The sulfur-degrading bacteria Pseudomonas in 0–23 cm of Y2 was 3.5 times as abundant as that of sulfur oxidizing bacteria (SOB), indicating remarkable remineralization of organic sulfur. The abundant SOB and 34S-depleted sulfate indicate considerable sulfur oxidation in 34–56-cm layer in Y2. In YO sediments, the highest abundance of Desulfotalea and the most enriched δ34SSO4 (35.2‰) and δ34SCRS (2.5‰) indicate the strongest sulfate reduction in 28-cm layer. High abundance of Pseudomonas indicates active remineralization of organic sulfur in 3–5-cm layer in YO. The medium δ34SSO4 and considerable abundance of SOB and sulfate-reducing bacteria (SRB) indicate concurrence of sulfur oxidation and sulfate reduction in other layers in YO. Therefore, a high level of organic matter input from penguin populations supported the diverse microbial community and transformations of sulfur in aquatic ecosystems in Antarctica.Keywords：sulfur and oxygen isotope;dissimilatory sulfate reduction;sulfur oxidation;sulfate-reducing bacteria;Antarctica4|1|0Updated：2023-04-27
- Abstract：The geochemical characteristics and potential controlling factors of colloidal Zn, Cd, and Pb in Huanghe (Yellow) River estuary (HRE), China were investigated. The three metals were highly variable over a range of spatiotemporal scales, comprehensively forced by various physical and biological processes. Total dissolved Zn, Cd, and Pb varied from 200.1 to 321.7, 2.6 to 4.1, and 0.5 to 1.0 nmol/L, respectively. Only one near-estuarine station of Zn had contamination factor values >1, which indicate the lower contaminant levels. Five dissolved species of Zn, Cd and Pb were fractionated, namely < 1 kDa, 1-3 kDa, 3-10 kDa, 10-100 kDa, and 100 kDa-0.45 njm. The < 1 kDa truly dissolved phase was the main fraction of the three dissolved metals (50%-62%), while the 100-kDa-0.45-njm high molecular weight colloidal fraction was dominant in their respective colloidal phase. Territorial input and sediment acted as important sources of strong ligands and natural colloids for the HRE water system. < 3-kDa Zn and Pb were susceptible to the dissolved oxygen, the behaviors of colloidal Zn and 3-10-kDa Pb were related to dissolved organic carbon (DOC). However, no significant correlation between each dissolved fraction of Cd and salinity, pH, temperature, colloidal organic carbon, and DOC was found in this study. Overall, these findings, completed by the evaluation of the dissolved species of Zn, Cd, and Pb at 10 sites over the river-sea mixing zone, provided new insights into the colloidal heterogeneity that affect metals geochemical features, migration and fate in estuaries.Keywords：colloidal heavy metal;size fraction;Huanghe (Yellow) River estuary;geochemical feature4|0|0Updated：2023-04-27
- Abstract：Polycyclic aromatic hydrocarbons (PAHs) are one of the most important groups in oil, and responsible for major toxic and/or carcinogenic impact on humans and wildlife. It is important to understand the behavior of PAHs in marine environment after an oil-spill incident. However, interaction between petroleum PAHs and microbial communities in a marine environment remains unclear. Therefore, a series of mesocosm experiments were conducted, in which water-accommodated fraction (WAF) of oil was generated to simulate an oil-spill scenario and to analyze the transport and behavior of marine oil spill containing PAHs with and without dispersants. Results indicate that the application of dispersant could increase the concentration of total PAHs in water column due mainly to significant increase in the concentration of high-molecular weight (HMW) PAHs at a lower removal rate. At the end of the 7-day experiment, significant amount of HMW PAHs were accumulated in sediment. In general, the application of dispersant did not increase the sediment uptake of PAHs but increased the PAHs concentration in water column.Keywords：polycyclic aromatic hydrocarbons (PAHs);marine oil spill;mesocosm;dispersants;degradation and transport4|1|0Updated：2023-04-27
- Abstract：Marine biofouling causes serious harms to surfaces of marine devices in transportation, aquaculture, and offshore construction. Traditional antifouling methods pollute the environment. A novel and green antifouling strategy was developed to prevent effectively the adhesion of bacteria and microalgae. An antifouling surface was fabricated via coating Turgencin BMox2 (TB) onto dopamine-modified 304 stainless steel (304 SS). The surface physical and chemical properties before and after modification were characterized by Fourier transform infrared spectrometer (FTIR), X-ray photoelectron spectrometer (XPS), contact angle measurement (CA), 3D optical profilometer, ellipsometer, and atomic force microscope (AFM). Antimicrobial peptide was coated onto the surface of 304 SS successfully, and the surface morphology and wettability of the modified sample were modified. Moreover, cytocompatibility of the peptide was evaluated by co-culture of peptide and cells, indicating promising cell biocompatibility at the modified sample surface. At last, antifouling performance and electrochemical corrosion were tested. Results show that the adhesion rates of Vibrio natriegens and Phaeodactylum tricornutum on the antifouling surface were reduced by 99.85% and 67.93%, respectively from those of untreated samples. Therefore, the modified samples retained superior corrosion resistance. The study provide a simply and green way against biofouling on ship hulls and marine equipment.Keywords：surface modification;antimicrobial peptide;corrosion resistance;antifouling performance4|0|1Updated：2023-04-27
Chemistry
- Abstract：The short term (hourly scale) variability of heterotrophic prokaryote (HP) vertical distribution and respiratory activity, was investigated in the north-western (NW) Mediterranean Sea. HP vertical distribution was determined on board by flow cytometry analysis of seawater samples collected by series of CTD casts. Cell counts and viability were determined for all samples. HP respiratory rates were determined later in the laboratory from filtered seawater samples (23 dm3) from 300Ƀ1 150-m depth. The average cell viability was 94.8%±2.2% (n=240). There was no accumulation of dead cells, due to quick decay of damaged cells. In the epipelagic layer, three HP groups were distinguished, two (HNA1, HNA2) whose cells exhibited a high nucleic acid content and one (LNA) with low nucleic acid content cells. HNA2 was most populated at 50 m but not detected at 90 m and below, presumably aerobic anoxygenic photoheterotrophic bacteria (AAPs). The variability in HP abundance was mainly confined in the upper 80 m. A few secondary peaks of HP abundance were observed (80Ƀ150 m) in connection with abundance troughs in the surface layer. HP cells were continuously present in a wide layer around 500 m (mean 191×103 cells/cm3). Below this layer, HP abundance randomly exhibited peaks, coupled to respiratory rate peaks. The HP abundance and variability in the water column was suppressed during a strong wind event. The observed sporadic variability was tentatively interpreted through a pulsed carbon-export mechanism induced by the microorganism production of dissolved polysaccharides, followed by flocculation and rapid sinking. This mechanism would thus contribute to (i) preventing organic matter accumulation in the epipelagic layer, (ii) seeding the water column with live HP cells, and (iii) supplying the aphotic water column with fresh and labile organic matter. This important vertical flux mechanism needs further observations and modelling.Keywords：north-western Mediterranean Sea;heterotrophic prokaryote (HP);cell viability;cell respiration;transparent exopolymeric particle (TEP);aggregation;flow cytometry4|0|0Updated：2023-04-27
- Abstract：The response of phytoplankton and its satellite bacteria to various concentrations (0.01%Ƀ10% v/v) of ethanol is studied. To elucidate the effect of ethanol, single-strains of phytoplankton (SSP) culture, pure strains of satellite bacteria isolated from nonaxenic SSP cultures, and Escherichia coli were screened. Results indicate that ethanol could promote the growth and photosynthetic efficiency (Fv/Fm) of SSP at 0.01% and the growth of satellite bacteria at 0.01%Ƀ1%. Nevertheless, ethanol inhibited the growth and Fv/Fm of SSP at 0.1%Ƀ1%, and killed bacteria and SSP at 10% concentration. Further investigation on a satellite bacterium (Mameliella alba) revealed that ethanol promotes growth by serving as a growth stimulant rather than a metabolic carbon source. The 16S rRNA gene amplicon indicated that all nonaxenic SSP cultures harbor distinct satellite bacteria communities where the SSP culture of Skeletonema costatum, Phaeodactylum tricornutum, and Dunaliella bardawil were dominated by bacteria genera of Marivita (~80%), Dinoroseobacter (~47%), and Halomonas (~87%), respectively, indicating that every SSP cultures have their own distinct satellite bacterial community. The bacteria family Rhodobacteraceae was dominant in the two marine diatoms, whereas Halomonadaceae was dominant in the saline green microalga. Compared to their respective controls, the supply of 0.5% ethanol to SSP cultures promoted the growth of the satellite bacteria but did not cause a significant difference in species composition of satellite bacteria. Therefore, a low concentration of ethanol can promote the growth of bacteria in a non-selective way. This study enriched our knowledge about the effect of ethanol on aquatic microbes and provided a baseline for basic and applied biotechnological research in the aquatic environment in the future.Keywords：aquatic microbes;bacteria diversity;ethanol effect;growth inhibition;growth stimulation4|0|0Updated：2023-04-27
Ecology
- Abstract：The microbial communities colonized on microplastics (MPs) have attracted widespread attention. However, few studies focused on the MPs impacts on mangrove ecosystems, particularly on bacterial communities. We investigated the MPs pollution in mangrove of Zhujiang (Pearl) River estuary (ZRE). To study the potential risk posed by MPs to the mangrove ecosystems, the differences in bacterial communities, functions, and complexity between MPs and sediment samples were reported for the first time. Microplastics (2 991±1 586 items/kg dry weight (dw)) in sediment were mainly fibers and polyethylene, mostly transparent, and in size less than 0.5 mm. Bacterial communities and functions significantly differed from MPs in mangrove sediment. Compared with sediment, MPs significantly enriched members of Proteobacteria, Bacteroidetes, and Actinobacteria, as well as the bacteria associated with plastic-degrading and human diseases on their surface, suggesting that microbial communities on MPs may promote MPs degradation and the spread of diseases, posing potential risk to mangrove ecosystems and human health. Although bacteria on MPs exhibited a lower diversity, the co-occurrence network analysis indicated that network of bacteria colonized on MPs was bigger and more complex than those of mangrove sediment, illustrating that MPs can act as a distinct habitat in this special ecosystem. This study provides a new perspective for increasing our understanding of microplastic pollution in mangrove ecosystems.Keywords：microplastic (MP);mangrove sediment;microbial community;bacterial function;co-occurrence network8|2|7Updated：2023-04-27
- Abstract：Although biofilm formation may promote growth, biofilms are not always beneficial to their hosts. The biofilm formation characteristics of Bacillus cereus WPySW2 and its changes at different temperatures were studied. Results show that B. cereus WPySW2 promoted the growth of Neoporphyra haitanensis (an economically cultivated seaweed) at 20 ℃ but accelerated algal rot at 28 ℃. Thicker B. cereus WPySW2 biofilms covered the surface of N. haitanensis thalli at 28 ℃, which hindered material exchange between the algae and surrounding environment, inhibited algal photosynthesis and respiration, and accelerated algal decay. Compared with planktonic bacteria, mature biofilm cells had lower energy consumption and metabolic levels. The biofilm metabolic characteristics of B. cereus WPySW2 changed significantly with temperature. High temperature accelerated biofilm maturation, which made it thicker and more stable, allowing the bacteria to easily adapt to environmental changes and obtain greater benefits from their host. High temperature did not affect the production or increased the abundance of toxic metabolites, indicating that the negative effects of B. cereus WPySW2 on algae were not caused by toxins. This study shows that increased temperature can transform a harmless bacterium into a detrimental one, demonstrating that temperature may change the ecological function of phycospheric bacteria by affecting their morphology and metabolism.Keywords：bacterial biofilm;Bacillus cereus WPySW2;Pyropia;function transformation;metabolize4|0|0Updated：2023-04-27
- Abstract：During low tide, the intertidal seagrass Enhalus acoroides is often exposed to high light and desiccation, which can seriously threaten its survival, at least partly by inhibiting photosystem Ⅱ (PSII) activity. The response of leaves of E. acoroides to high light and desiccation was compared for seedlings and mature plants. Results show that the resistance of seedling and mature leaves to high light was quite similar, but to desiccation was very different. Seedling leaves were more sensitive to desiccation than the mature plant leaves, but had better water retention. The damage of desiccation to seedling leaves was mainly caused by dehydration, whereas that to mature plant leaves was caused by hypersaline toxicity. The recovery rate of PSII of seedling leaves was significantly slower than that of the mature plants after the stresses disappeared, which may at least partly contribute to seedling mortality in the wild. In addition, compared to high light, desiccation seriously inhibited the recovery rate of PSII activities even if the leaves became fully rehydrated to their normal relative water content (RWC) in the following re-immersion. Desiccation inhibited the recovery rate of RC/CSM (reaction center per cross section (at t=tFm)) to decrease the production of assimilatory power, which maybe the cause of the slower PSII recovery in desiccation treatments. This study demonstrates that desiccation particularly coupling with high light have a very negative effect on the PSII of E. acoroides during low tide and the sensitivity of seedlings and mature plants to desiccation is significantly different, which have important reference significance to choose an appropriate transplanting depth where seedlings and mature plants of E. acoroides not only receive sufficient light for growth, but also that minimize desiccation stress during low tide.Keywords：Enhalus acoroides;high light;desiccation;photosystem Ⅱ4|0|0Updated：2023-04-27
- Abstract：To date, little attention has been paid to the effects of organophosphate esters (OPEs) pollution on aquacultural environment and aquatic product safety. Huanghe (Yellow) River delta area is one of the largest aquaculture centers in China, where ecological security protection is crucial in the national strategy of China. To explore the pollution characteristics, bioaccumulation, and health risks of OPEs in aquaculture farms in the Huanghe River delta and natural water bodies in the adjacent seas, five species of organisms from different farm types nearby the Huanghe River delta, and the corresponding culture water and sediments were sampled in this study. The total concentrations of Σ13OPEs in water, sediments, and organisms were 51.53–272.18 ng/L, 52.63–63.17 ng/g dry weight (dw), and 46.82–108.90 ng/g dw, respectively. Among the five types of culture ponds, the water samples from the swimming crab and hairy crab culture ponds exhibited higher OPEs, the concentration of OPEs in the sediments from the few ponds was relatively balanced, and the OPEs in the organism from the holothurian ponds was higher. Tris (1, 3-dichloro-2-isopropyl phosphate) (TDCP) was the main contaminant in water samples and tripropyl phosphate (TPrP) in sediments and organisms. However, trisphenyl phosphate (TPhP) showed the strongest bioaccumulation ability, followed by 2-ethylhexyl diphenyl phosphate (EHDPP) and TPrP. The bioaccumulation capacities of the five species were as follows: prawn > holothurian > hairy crab > swimming crab > carp. These five types of organisms, as main seafood in human consumption, were at low risk of negative impacts of pollution. However, the risk from the mixture of organophosphate flame retardants (OPFRs) still requires more attention due to the increasing consumption and production in the world.Keywords：organophosphate esters (OPEs);aquaculture farms;bioaccumulation;health risk assessment4|0|0Updated：2023-04-27
- Abstract：The complete mitogenome of Parachiloglanis hodgarti was sequenced and characterized, which is the first mitogenome of the genus Parachiloglanis within Sisoridae. The mitogenome is 16 511-bp long and included 13 protein-coding genes, 22 transfer RNAs, two ribosomal RNAs, and one control region. The genome composition was A+T biased (58.64%) and exhibited a positive AT-skew (0.095) and a negative GC-skew (-0.283). Compared with other Sisoridae fishes, the characteristics of nucleotide skews, codon usage, and amino acid usage of the P. hodgarti mitogenome are more similar to those of non-Glyptosternoid fishes. Furthermore, the phylogenetic trees show that Sisoridae fishes fall into four major clades and P. hodgarti (Clade Ⅰ) is basal to the Sisoridae family, forming a sister clade to the Glyptosternoids (Clade Ⅳ). The topological structures constructed in this study raised doubts over the traditional classification system. These results will help better understand the features of the P. hodgarti mitogenome and provide a reference for further phylogenetic research on Sisoridae species.Keywords：Parachiloglanis hodgarti;mitogenomes;Sisoridae;glyptosternoids;phylogenetic relationship5|1|0Updated：2023-04-27
- Abstract：Insulin-like growth factors (IGFs) are key regulators of development and growth. Here, we characterized the igf2 gene from olive flounder (Paralichthys olivaceus) and determined its temporal and spatial expression. We set up an in-vitro protein expression system in eukaryotic human embryonic kidney (HEK293T) cells and explored its effects on cell proliferation. The flounder igf2 cDNA contained a 648-bp open reading frame (ORF) encoding a protein of 215 amino acids (aa), which spanned the complete signal peptide (47 aa), mature peptide (70 aa), and E domain (98 aa). In adult flounder, igf2 mRNA was detected in all selected tissues. In early development, igf2 mRNA was detected throughout development from unfertilized eggs to hatching-stage embryos. In-situ hybridization analysis indicated that igf2 mRNA was specially expressed in the brain region, floor plate, hypochord, otic vesicle, and pectoral fin during embryogenesis. Western blotting analysis indicated that the soluble recombinant flounder IGF2 protein was successfully produced through eukaryotic expression in HEK293T cells. In addition, the recombinant IGF2 protein significantly promoted the proliferation of human cervical carcinoma (HeLa) and HEK293T cells. These results provide new information about the structural and functional conservation, expression patterns, and biological activity of the igf2 in teleosts.Keywords：aquaculture;flatfish;igf2;proliferation4|0|0Updated：2023-04-27
- Abstract：Plankton size structure is crucial for understanding marine ecosystem dynamics and the associated biogeochemical processes. A fixation step by acid Lugol's solution has been commonly employed to preserve plankton samples in the field. However, the acid Lugol's solution can bias the estimation of size structure and the preserved plankton size structure can vary with time. Here, we explore the impact of sample storage time on the size-structure of the plankton community preserved by Lugol's solution. Two short-term experiments and one long-term experiment were conducted to explore the change of plankton community size structure with the storage time: covering from a week to a month, and to nearly seven months based on particle-size data obtained by continuous Flow Cytometer and Microscope (FlowCAM) measurements. We found a linear change of plankton size with the storage time in short-term periods (less than 3 months) with a decrease of the slope but an increase of the intercept for the normalized biomass size spectrum (NBSS). However, there were opposite trends for NBSS with increasing slope but decreasing intercept after 3 months. The potential causes of the distinct patterns of the NBSS parameters are addressed in terms of the interplay between particle aggregation and fragmentation. We found large changes in plankton biovolume and abundance among different size classes, which may indicate a distinct effect of acid Lugol's solution on various plankton size classes. The mechanism driving temporal change in the size-structure of the Lugolfixed plankton community was further discussed in terms of particle aggregation and fragmentation. Finally, we emphasize that the effect of storage time should be taken into account when interpreting or comparing data of plankton community acquired from samples with various storage durations.Keywords：Lugol's;plankton;size structure;Flow Cytometer and Microscope (FlowCAM)4|0|0Updated：2023-04-27
- Abstract：A sulfated galactofucan designated as UpG was obtained from the brown algae Undaria pinnatifida by calcium chloride extraction. Chemical analyses showed that UpG is composed of galactose and fucose at a high sulfation level. Low-molecular weight UpGP-0.5 was prepared from UpG through acid hydrolysis for structure characterization. The backbones of UpG are determined to be α-(1,3)-Fuc, α-(1,4)-Gal, α-(1,3)-Gal, and α-(1,6)-Gal by GC-MS, FT-IR, NMR, and LC-MS analyses. Sulfate groups are modified at C2 and/or C4 of fucose and C3 and/or C4 of galactose. UpG could partially lower blood sugar and serum lipid levels in type 2 diabetic mice. Moreover, UpG treatment regulates the abundance of some specific gut microbiota, such as enriching the abundance of Muribaculum and Christensenellaceae, and reducing that of Bilophila, Tannerellaceae, Candidatus Saccharimonas and Anaerotruncus. The findings characterized the detailed structure of a sulfated galactofucan and investigated its potential for the treatment of type 2 diabetes mellitus.Keywords：Undaria pinnatifida;galactofucan;structure;gut microbiota;diabetes4|0|0Updated：2023-04-27
- Abstract：A new species and a new record of free-living marine nematode of genus Diplolaimelloides (Monhysteridae) inhabiting the sediment of mangrove reservation in Shenzhen, China are described and illustrated. Diplolaimelloides contortus sp. nov. is characterized by the combination of the following characters: ocelli present; four pairs of post-cloacal papillae arranged in (2+2) pattern, two midway on bursa and two near posterior extremities; spicules complicated in shape, twisted and curved at middle portion; gubernaculum wedge-shaped, with distal dorsal ridge well cuticularized, proximal dorsal ridge obscure sleeve-like, proximal end wrap the spicule; vulva located at 52.1%–53.6% of body length; male tail slender, 10.0–11.4 times of anal body diameter, and female tail long filiform, 13.1–13.6 times of anal body diameter. Diplolaimelloides delyi Andrássy, 1958 is first recorded from China and redescribed in detail, it differs from the original description by Andrássy in 1958 for having larger body size of male, shorter tail, and posterior situation of vulva. However, it is much conform to the redescription to specimens from East Pakistan by Timm in 1966, except for shorter tail in female and absent pre-anal seta. Specimens are deposited in the Institute of Oceanology, Chinese Academy of Sciences.Keywords：taxonomy;Diplolaimelloides contortus sp. nov.;Diplolaimelloides delyi Andrássy, 1958;mangrove nematode;China7|0|0Updated：2023-04-27
- Abstract：We detailed the valve morphology of five new species of diatom genus Nupela from wetwall communities in Yunnan Province, China, with light and scanning electron microscope. The five new species demonstrate great variability within the genus, as three of them are biraphid and two are monoraphid. In addition, variation was noted in the structure of internal proximal raphe ends, with some species having anchor-shaped ends and other species have hooked ends. The genus Nupela has grown considerably in 30 years since it was first proposed, going from a monotypic genus to over 85 taxa. Diagnosis of the genus is based on the presence of an external covering over the areolae. We discussed the systematic placement of Nupela within the naviculoid diatoms. Yunnan Province appears to harbor many endemic diatom taxa, and many regions of the province have yet to be studied.Keywords：Nupela;scanning electron microscope (SEM);Yunnan;new species;morphology;China;Bacillariophyceae5|0|0Updated：2023-04-27
Biology
- Abstract：Glycogen, amino acids, fatty acids, and other nutrient components affect the flavor and nutritional quality of oysters. Methods based on near-infrared reflectance spectroscopy (NIRS) were developed to rapidly and proximately determine the nutrient content of the Pacific oyster Crassostrea gigas. Samples of C. gigas from 19 costal sites were freeze-dried, ground, and scanned for spectral data collection using a Fourier transform NIR spectrometer (Thermo Fisher Scientific). NIRS models of glycogen and other nutrients were established using partial least squares, multiplication scattering correction, first-order derivation, and Norris smoothing. The RC values of the glycogen, fatty acids, amino acids, and taurine NIRS models were 0.967 8, 0.931 2, 0.913 2, and 0.892 8, respectively, and the residual prediction deviation (RPD) values of these components were 3.15, 2.16, 3.11, and 1.59, respectively, indicating a high correlation between the predicted and observed values, and that the models can be used in practice. The models were used to evaluate the nutrient compositions of 1 278 oyster samples. Glycogen content was found to be positively correlated with fatty acids and negatively correlated with amino acids. The glycogen, amino acid, and taurine levels of C. gigas cultured in the subtidal and intertidal zones were also significantly different. This study suggests that C. gigas NIRS models can be a cost-effective alternative to traditional methods for the rapid and proximate analysis of various slaughter traits and may also contribute to future genetic and breeding-related studies in Pacific oysters.Keywords：Pacific oyster;Crassostrea gigas;near-infrared reflectance spectroscopy (NIRS);nutrient composition;rapid determination4|0|0Updated：2023-04-27
- Abstract：The appropriate reference gene is a prerequisite for accurate normalization of gene expression level, and research on suitable reference genes in clam Cyclina sinensis is scarce. To improve the situation, we selected five commonly used housekeeping genes, including β-actin, Elongation factor 1-α (EF1-α), Glyceraldehyde-3-phosphate dehydrogenase (GAPDH), 40S ribosomal protein S18 (RPS18), and Tubulin α (TUB-α), then evaluated their expression stability in different adult tissues and under different experimental treatments (salinity stress and Vibrio parahaemolyticus infection). Their expression stability was analyzed by three frequently used programs, geNorm, NormFinder, and BestKeeper. This analysis indicated that multiple genes should be used for normalization, and we concluded that the reference gene combination GAPDH-RPS18-β-actin, should be used for qRT-PCR analysis in different tissues of C. sinensis under normal physiological conditions. For the clams under salinity stress and Vibrio infection, EF1-α-GAPDH-RPS18 was recommended as the gene combination for qRT-PCR normalization. TUB-α was generally poorly ranked by all programs, and should not be used in future studies. This study should provide fundamental support for accurate quantitative gene expression analysis of this species.Keywords：Cyclina sinensis;reference gene;different tissues;salinity stress;Vibrio infection4|0|0Updated：2023-04-27
- Abstract：Dissolved oxygen (DO) is one of most important factors which affect wide range physiologic features of fish, including immune responses and intestinal bacterial community. However, the underlying mechanisms remain enigmatic. To address this question, the intestinal bacterial community compositions and the immune features of Atlantic salmon (Salmo salar) grown in recirculating aquaculture systems (RAS) were characterized. Fish were reared under different DO saturation levels, e.g., 200% saturation named high group (H), 100% saturation named control group (CK), and 60% saturation named lower group (L). Large variations in the operational taxonomic units (OTUs) frequency distribution for the intestinal bacterial community of Atlantic salmon were observed. The intestinal bacterial community of all groups was dominated mainly by three phyla, e.g., Proteobacteria, Firmicutes, and Bacteroidetes. Interestingly, Acinetobacter baumannii, an opportunistic pathogen of salmon was increased significantly in L group. We further monitored the immunity features of fish under different DO levels. The results show that leucocyte number, cortisol level, the expressions of interleukin-1β (IL-1β), Toll-like receptor 4 (TLR4), and nucleotide-binding oligomerization domain like protein 2 (NOD2) were higher at significant levels in the L group than those in the other two groups. TLR4 and NOD2 are usually related with the bacterial infections; therefore, it is reasonable to believe that the stronger immune responses observed in the L group might be related with the higher abundance of A. baumannii in the intestine of Atlantic salmon. Overall, these findings demonstrated that low DO level may induce stronger immunity responses in Atlantic salmon.Keywords：Atlantic salmon;dissolved oxygen (DO);immune responses;microbiota;intestine4|2|0Updated：2023-04-27
- Abstract：Long non-coding RNAs (lncRNAs) are a class of transcripts longer than 200 bp, which have been emerged as essential regulators in numerous biological processes. Black rockfish (Sebastes schlegelii) is an economic fish that widely cultured in the coastal areas of China, Japan, and South Korea. With the expansion of aquacultural scale, various pathogens have threatened its industry and reduced its economic values. It has been reported that lncRNA were involved in the immune response and metabolic pathway in teleost, while no study is available on identification and functional analysis of lncRNAs in black rockfish so far. Herein, this study was performed to identify lncRNAs in the intestine of black rockfish after Edwardsiella tarda infection. In our results, a total of 9 311 lncRNAs were identified through high-throughput sequencing, and 102 lncRNAs were significantly regulated following challenge, which were predicted to target 3 348 mRNAs. Results of Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses of these target genes showed they were function in catalytic activity, hydrolase activity, defense response and peptidase activity, which involved in metabolic pathways and immune related pathways. In addition, 47 lncRNAs and 8 differentially expressed mRNAs (DEmRNAs) showed co-expression at two or more infection time points with metabolism and immunity functions. Moreover, real-time quantitative PCR (qRT-PCR) was performed to verify the reliability of sequencing gene expression analysis results. This research laid the foundation for further investigation of the regulatory roles of lncRNAs in the intestinal immune response of black rockfish.Keywords：long non-coding RNA;mRNA;intestine;Sebastes schlegelii;Edwardsiella tarda5|0|0Updated：2023-04-27
- Abstract：Aeromonas hydrophila is a Gram-negative pathogen that can infect various fish, including largemouth bass (Micropterus salmoides), which have caused huge economic losses. In present study, largemouth bass anti-A. hydrophila antibodies were produced, then a highly immunogenic outer membrane proteins, AHA_3793, was identified by combined western blotting and mass spectrometry analysis. Moreover, AHA_3793 was expressed, and its immunogenicity was further verified by western blotting. Subsequently, the protective efficacy of AHA_3793 were evaluated in largemouth bass. The results showed that rAHA_3793 could produce a relative percentage survival (RPS) of 61.76% for largemouth bass against A. hydrophila challenge. ELISA analysis showed the specific serum antibodies of largemouth bass against rAHA_3793 and A. hydrophila in vaccinated group in weeks 4 and 5 after immunization were significantly higher than those in control group, which suggested that rAHA_3793 induced production of specific serum antibodies against rAHA_3793 and A. hydrophila. The qRT-PCR analysis showed that expressions of CD4-2 and MHC IIα were also significantly up-regulated after immunization. These results collectively demonstrated that rAHA_3793 could induce a strong humoral immune response of largemouth bass, and then produce high immune protection effects against A. hydrophila infection.Keywords：Micropterus salmoides;Aeromonas hydrophila;AHA_3793;subunit vaccine;immune response4|0|1Updated：2023-04-27
Aquaculture and Fisheries
Erratum
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