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Volume 40 ， Issue 3 ， 2022
- Abstract：A series of non-hydrostatic, non-linear numerical simulations were carried out to investigate the generation and evolution of internal solitary waves (ISWs) through the interaction of a barotropic tidal current with an ice keel in the Arctic Ocean. During the interaction process, the internal surge was generated at first, and then the wave gradually steepened due to non-linearity during its propagation away from the ice keel. The internal surge eventually disintegrated into multi-modal and rank-ordered ISW packets with the largest having an amplitude of O(10) m. Sensitivity experiments demonstrated that the ISWs' amplitudes and energy were proportional to the varying ice keel depths and barotropic tidal flow amplitudes, but were insensitive to the changing ice keel widths. Typical ISWs can enhance the turbulent dissipation rate of O(10-6) W/kg along their propagation path. Further, heat entrainment induced by the wave-ice interaction can reach O(10) MJ/m per tidal cycle. This study reveals a particular ISW generation mechanism and process in the polar ice environment, which could be important in impacting the energy transfer and heat balance in the Arctic Ocean.Keywords：internal solitary wave (ISW);barotropic tidal flow;ice keel;the Arctic Ocean7|0|1Updated：2023-05-20
- Abstract：Upper ocean mixing plays a key role in the atmosphere-ocean heat transfer and sea ice extent and thickness via modulating the upper ocean temperatures in the Arctic Ocean. Observations of diffusivities in the Arctic that directly indicate the ocean mixing properties are sparse. Therefore, the spatiotemporal pattern and magnitude of diapycnal diffusivities and kinetic energy dissipation rates in the upper Arctic Ocean are important for atmosphere-ocean heat transfers and sea ice changes. These were first estimated from the Ice-Tethered Profilers dataset (2005–2019) using a strain-based fine-scale parameterization. The resultant mixing properties showed significant geographical inhomogeneity and temporal variability. Diapycnal diffusivities and dissipation rates in the Atlantic sector of the Arctic Ocean were stronger than those on the Pacific side. Mixing in the Atlantic sector increased significantly during the observation period; whereas in the Pacific sector, it weakened before 2011 and then strengthened. Potential impact factors include wind, sea ice, near inertial waves, and stratification, while their relative contributions vary between the two sectors of the Arctic Ocean. In the Atlantic sector, turbulent mixing dominated, while in the Pacific sector, turbulent mixing was inhibited by strong stratification prior to 2011, and is able to overcome the stratification gradually after 2014. The vertical turbulent heat flux constantly increased in the Atlantic sector year by year, while it decreased in the Pacific sector post 2010. The estimated heat flux variability induced by enhanced turbulent mixing is expected to continue to diminish sea ice in the near future.Keywords：mixing;the Arctic Ocean;near-inertial waves;stratification;heat flux10|0|1Updated：2023-05-20
- Abstract：Seasonal variations of the equatorial undercurrent (EUC) termination in the Eastern Pacific, and their mechanism were examined using the Estimating the Circulation and Climate of the Ocean, Phase Ⅱ (ECCO2). The ECCO2 reproduced a weak and shallow eastward EUC east of the Galapagos Islands, with annual mean transport of half of EUC to the west of the Islands. The diagnosis of zonal momentum equation suggests that the zonal advection (nonlinear terms) drives the EUC beyond the Islands rather than the pressure gradient force. The EUC in the Far Eastern Pacific has the largest core velocity in boreal spring and the smallest one in boreal summer, and its volume transport exhibits two maxima in boreal spring and autumn. The seasonal variability of the EUC in the Eastern Pacific is dominated by the Kelvin and Rossby waves excited by the zonal winds anomalies in the central and Eastern Pacific that are associated with the seasonal relaxation or intensification of the trade wind. In the Far Eastern Pacific to the east of 120°W, the eastward propagation Kelvin waves play a dominate role in the seasonal cycle of the EUC, results in a semiannual fluctuation with double peaks in boreal spring and autumn. A construction of water mass budget suggests that approximately 24.1% of the EUC water east of 100°W has upwelled to the mixed layer by 0.35 m/d. The estimated upwelling is strongest during boreal autumn and weakest during boreal winter. It is also found that approximately 42.6% of the EUC turns westward to feed the south equatorial current (SEC), 13.2% flows north of the equator, and 20.1% flows south of the equator, mainly contributing to Peru-Chile undercurrent.Keywords：equatorial undercurrent termination;Eastern Pacific Ocean;Estimating the Circulation and Climate of the Ocean, Phase Ⅱ (ECCO2);Peru-Chile undercurrent;Galapagos Islands6|0|0Updated：2023-05-20
- Abstract：The classical Lagrangian particle tracing method is widely used in the evaluation of the ocean annual subduction rate. However, our analysis indicates that in addition to neglecting the effect of mixing, there are two possible deviations in the method: one is an overestimation due to not considering that the amount of subducted water at the source location may be inadequate during the late winter of the first year when the mixed layer becomes shallow; the other one is an underestimation due to the neglect of the effective subduction caused by strong vertical pumping. Quantitative analysis shows that these two deviations mainly exist in the low-latitude subduction areas of the South Pacific and South Atlantic. The two deviations have very similar distribution areas and can partially offset each other. However, the overall deviation is still large, and the maximum relative deviation ratio can reach 50%; therefore, it cannot be ignored.Keywords：subduction rate;Lagrangian particle tracing method;mixed layer;tropical water;eastern subtropical mode water7|0|0Updated：2023-05-20
- Abstract：The full fluxes and associated air-sea variables based on three months of operational buoy observations in the East China Sea (ECS) in summer 2020 were analyzed for the first time. The surface net heat flux (Qnet) was positive (139.7±77.7 W/m2) and was dominated by the combined effects of solar shortwave radiation (SW) and latent heat fluxes (LH). The mean heat flux components of 4 reanalysis datasets (NCEP2, MERRA-2, CFSR, and ERA5) and buoy data were compared to assess the mean ability of the modeling/reanalysis simulation. Among the four components of air-sea flux, SW was the best simulated, while LH was the worst simulated. The longwave radiation (LW) and LH values from reanalysis were higher than those from buoy data, especially LH. The high LH resulted in low Qnet. Furthermore, the 4 reanalysis datasets were compared with the buoy dataset. Among all flux products, the difference in radiation flux was the smallest, while that in the turbulent flux was the greatest. The observed variables related to turbulent flux were analyzed to help determine the cause of the flux discrepancies. High wind speeds were the main cause of this difference. Using the variables provided by the reanalysis data and the same bulk formulas of the Coupled Ocean-Atmospheric Response Experiment (COARE 3.0), we found that the recalculated sensible heat flux (SH) and LH were closer to the observed heat fluxes than the direct model outputs. The significant differences between these methods could account for the discrepancies among different data. Among all air-sea flux products, the air-sea flux in ERA5 was closer to the in-situ observations than the other products. The comparison results of reanalysis data provide an important reference for more accurate studies of the summer heat flux in the ECS at the synoptic and climatic scales.Keywords：buoy observations;East China Sea;air-sea turbulent heat flux;radiative flux;reanalysis6|0|0Updated：2023-05-20
- Abstract：Typhoon has an impact on an estuary and coastal environment. However, the present research lacks the detailed description of material transport processes during typhoon passage, such as the transport channels and barriers in the course of material transport and material accumulation area, etc. Therefore, Lagrangian coherent structures (a method developed for describing the transport structure of fluids in recent years) was introduced to investigate and predict the floating material and debris transport process in the Laizhou Bay, Bohai Sea, during typhoon Lekima in 2019. Results show that the Lagrangian coherent structure could well explain the complex flow phenomena in the bay. During the typhoon, the general direction of floating material transport in the Laizhou Bay was anticlockwise. There was a channel for material transport in the northwest and south of the bay, and there are transportation obstacles in the northeast-southwest direction in the middle of the bay. Therefore, the typhoon might worsen the water quality. These results provide references for precise countermeasures to control the formulation of pollution in the Laizhou Bay.Keywords：material transport;typhoon;Lagrangian coherent structures;Laizhou Bay6|0|2Updated：2023-05-20
- Abstract：We examined the influences of the wind field and wave-current interaction (WCI) on the numerical simulation results of typhoon-induced wind waves in the northern East China Sea (NECS) using the coupled Simulating Waves Nearshore+Advanced Circulation (SWAN+ADCIRC) model. The simulations were performed during two typhoon events (Lekima and Muifa), and two widely used reanalysis wind fields, the Climate Forecast System Version 2 (CFSv2) from the National Centers for Environmental Prediction (NCEP) and the fifth-generation European Centre for Medium-Range Weather Forecasts (ECMWF) Reanalysis (ERA5), were compared. The results indicate that the ERA5 and CFSv2 wind fields both reliably reproduced the wind variations measured by in-situ buoys, and the accuracy of the winds from ERA5 were generally better than those from CFSv2 because CFSv2 tended to overestimate the wind speed and the simulated significant wave height (SWH), particularly the peak SWH. The WCI effects between the two wind field simulations were similar; these effects enhanced the SWH throughout the nearshore NECS during both typhoons but suppressed the SWH on the right side of the Typhoon Muifa track in the deep and offshore sea areas. In summary, variations in the water depth and current propagation direction dominate the modulation of wave height.Keywords：typhoon track;significant wave height;wave-current interaction;the northern East China Sea7|0|2Updated：2023-05-20
- Abstract：There are considerable amounts of offshore oil/gas fields in the South China Sea (SCS), and for potential oil spill events in this area, dispersants may provide a reliable large-scale response when the preferable option of recapturing the oil cannot be achieved. In this paper, effect of chemical dispersants on underwater oil transport is investigated with an underwater oil spill model. Since the model is an adaption of an existing one, we first calibrate it by comparing the model result with echo-sounder data that were observed during the "DeepSpill" experiment with crude oil/LNG (liquefied natural gas) discharge. Then, with the hydrodynamic data provided by an operational forecasting system and the drilling data obtained from offshore platforms in the SCS, we apply the model to a hypothetical spill case, and examine the difference in oil distribution in water column caused by subsea dispersant application. The model results can provide valuable reference for contingency plan makers to make an efficient emergency response to potential underwater oil spill accidents in the SCS.Keywords：underwater oil spill;numerical simulation;chemical dispersants;South China Sea;contingency planning6|0|0Updated：2023-05-20
Physics
- Abstract：Cold seeps spread worldwide along the continental margins, which are closely related to the exploration of gas hydrates. Cold-seep carbonates have been reported to record the nature of seepage, including fluid source, sedimentary environment, and variation of seepage activity. We investigated the morphology, mineralogy, element compositions, and carbon and oxygen isotopes of 15 cold-seep carbonates collected from the Shenhu area, and compared them with 2 carbonates from the Haima cold seep, the South China Sea (SCS), to promote our knowledge of cold-seep system in SCS. Most of the Shenhu carbonates exhibit crust morphology, and some are in the form of chimneys and blocks. Their absolute (20%–65%) and relative carbonate mineral contents (mainly aragonite and calcite, with minor samples containing dolomite) vary significantly, indicating the multi-stage methane leakage in our study area. Some samples show a slight negative Ce anomaly, suggesting either the mixing of seawater or variation of the redox condition during the precipitation; the cooccurrence of strongly enriched U and Mo demonstrates anoxic condition during precipitation. The mixed genetic methane source was interpreted by δ13C of the Shenhu carbonates to range from -22.34‰ to -59.30‰ Vienna PeeDee Belemnite (VPDB), and the slight 18O-enrichment imprinted on the carbonates suggests the possible influence from hydrate dissociation. The Haima carbonates, with biogenic methane as the main gas source, were presumably formed in a stronger fluid flux by compared with our Shenhu samples.Keywords：cold-seep carbonates;geochemistry;sedimentary environment;fluid source;Haima cold seep;Shenhu area;South China Sea6|0|0Updated：2023-05-20
Geology
- Abstract：The multi-point simultaneous long-term measurement of CO2 concentration in seawater can provide more-valuable data for further understanding of the spatial and temporal distribution of CO2. Thus, the requirement for a low-cost sensor with high precision, low power consumption, and a small size is becoming urgent. In this work, an in-situ sensor for CO2 detection in seawater, based on a permeable membrane and non-dispersive infrared (NDIR) technology, is developed. The sensor has a small size (Ф 66 mm×124 mm), light weight (0.7 kg in air), low power consumption (< 0.9 W), low cost (< US$1 000), and high-pressure tolerance (< 200 m). After laboratory performance tests, the sensor was found to have a measurement range of (0–2 000)×10-6, and the gas linear correlation R2 is 0.99, with a precision of about 0.98% at a sampling rate of 1 s. A comparison measurement was carried out with a commercial sensor in a pool for 7 days, and the results showed a consistent trend. Further, the newly developed sensor was deployed in Qingdao nearshore water for 35 days. The results proved that the sensor could measure the dynamic changes of CO2 concentration in seawater continuously, and had the potential to carry out long-term observations on an oceanic platform. It is hoped that the sensor could be applied to field ocean observations in near future.Keywords：in-situ sensor;dissolved CO2;long-term measurement;permeable membrane;non-dispersive infrared (NDIR);low-cost6|0|0Updated：2023-05-20
Chemistry
- Abstract：Ocean acidification (OA) and global warming-induced water column stratification can significantly alter phytoplankton-related biological activity in the marine ecosystem. Yet how these changes may play out in the tropical Indian Ocean remains unclear. This study investigated the ecological and metabolic responses of the different phytoplankton functional groups to elevated CO2 partial pressure and nitrate deficiency in two different environments of the eastern Indian Ocean (EIO). It is revealed that phytoplankton growth and metabolic rates are more sensitive to inorganic nutrients rather than CO2. The combined interactive effects of OA and N-limitation on phytoplankton populations are functional group-specific. In particular, the abundance and calcification rate of calcifying coccolithophores are expected to be enhanced in the future EIO. The underlying mechanisms for this enhancement may be ascribed to coccolithophore's lower carbon concentrating mechanisms (CCMs) efficiency and OA-induced [HCO3-] increase. In comparison, the abundance of non-calcifying microphytoplankton (e.g., diatoms and dinoflagellates) and primary productivity would be inhibited under those conditions. Different from previous laboratory experiments, interspecific competition for resources would be an important consideration in the natural phytoplankton populations. These combined factors would roughly determine calcifying coccolithophores as "winners" and non-calcifying microphytoplankton as "losers" in the future ocean scenario. Due to the large species-specific differences in phytoplankton sensitivity to OA, comprehensive investigations on oceanic phytoplankton communities are essential to precisely predict phytoplankton ecophysiological response to ocean acidification.Keywords：natural phytoplankton community;ocean acidification;coccolithophore calcification;primary productivity;eastern Indian Ocean9|0|0Updated：2023-05-20
- Abstract：Phytoplankton are not only the main bearer of the nitrogen cycle, but also a key link driving nitrogen cycle. However, most phytoplankton cannot directly use N2, and they must uptake nitrogenous nutrients (ammonium, nitrate, and urea) to meet their photosynthesis needs. We examined the uptake characteristics of several nitrogenous substrates using stable isotope technique and identified the potential nitrogen transformations in the Fenhe River. Results revealed that spring phytoplankton community composed of mainly Fragilaria, Ulothrix, Microcystis, and Synedra. Urea can meet the spring partial nitrogen requirement of phytoplankton. The large uptake rate of urea depended on urease, chlorophyll a, and nitrate concentrations as shown in random forest models. Cyanobacteria explained more than 42.8% of the total abundance at all sites in summer. Upstream was dominated by Actinastrum, and Chlorella was relevant in the downstream section. The uptake rates of ammonium were higher than those of nitrate and urea. In addition, the random forest model demonstrated that ammonium, urease, and dissolved oxygen (DO) were the major contributors to the ammonium uptake rates. Ammonium was taken up preferentially in autumn and phytoplankton (Cyclotella, Chlorella, and Pseudanabaena) appeared to be able to respond to changes in nitrogen forms by adjusting their community composition. Structural equation models demonstrated that temperature-induced changes in DO directly affected the transformations of different forms of nitrogen. At the same time, dissolved organic carbon can directly act on nutrients and then indirectly affect enzyme activity. There were great differences in the positive and negative effects of different paths in the process of nitrate reduction to nitrite and then reduction to ammonium in time and space. These findings provide a better understanding of the underlying mechanism of nitrogen uptake and the influences of interaction between environmental variables on nitrogen transformations in urban river ecosystems.Keywords：phytoplankton;environmental variables;nitrogen uptake;transformation;urban river6|0|1Updated：2023-05-20
- Abstract：Algicidal bacteria have been frequently isolated from algal blooming areas. However, knowledge regarding the microbial communities coexisting with microalgae and their potential application in preventing harmful algal blooms (HABs) is limited. In this study, we investigated the composition of the microbial community coexisting with harmful alga Karenia mikimotoi and its responses to algal control via nutrient stimulation or by adding algicidal strain in microcosms. The microorganisms inhabiting the K. mikimotoi culture consisted of 24 identified phyla, including dominant Proteobacteria (relative abundance 76.24%±7.28%) and Bacteroidetes (22.67%±8.32%). Rhodobacteraceae, Phaeodactylibacter, and Maritimibacter predominated during the algal cultivation. Both the added nutrient and fermentation broth of algicidal strain Pseudoalteromonas QF1 caused a massive death of K. mikimotoi and substantial changes in the coexisting microbial community, in which Rhodobacteraceae and Phaeodactylibacter significantly decreased, while Halomonas and Alteromonas increased. Core operational taxonomic units (OTUs) analysis indicated that 13 OTUs belonging to Rhodobacteraceae, Maritimibacter, Marivita, Nisaea, Phaeodactylibacter, Citreicella, Halomonas, Alteromonas, Marinobacter, Muricauda, and Pseudoalteromonas dominated the changes of the microbial communities observed in the K. mikimotoi culture with or without treatments. Collectively, this study indicated that microbial community inhabiting K. mikimotoi culture includes potential algicidal bacteria, and improves our knowledge about microbial community succession during biocontrol of K. mikimotoi via nutrient stimulation or by adding isolated algicidal strains.Keywords：Karenia mikimotoi;microbial community;nutrient stimulation;algicidal bacteria;Pseudoalteromonas6|0|0Updated：2023-05-20
- Abstract：Denitrifying bacteria are a crucial component of aquatic ecosystem in nitrogen cycle. However, the denitrifying bacterial community dynamics and structure in epiphytic biofilms remain unexplored. The abundance of denitrification gene (nir) and structure of nirS-denitrifying bacterial community in the epiphytic biofilms collected in July and November of 2018 from a typical plateau lake (Caohai Wetland, Guizhou, China) were studied by Real-time Quantitative Polymerase Chain Reaction (qPCR) and high-throughput sequencing. Results show that the gene abundance of nirK was higher than that of nirS (P < 0.05), and it was significantly different during the growth period (July) than the decline period (November). The denitrifying bacterial species was similar in the two months and shared 76.18% of OTUs. Proteobacteria (56.55%±22.15%) was the dominant phylum in all the samples. Epiphytic biofilms between growth period and decline period displayed significantly different microbial community structures due to differences in species abundance. Water temperature was the crucial factor that affected the denitrifying microbial community structure in our study. Environmental factors explain only partially the dynamic characteristics of denitrifying microbial communities, implying that the stochastic processes affected the construction of denitrifying microbial communities. As the null model analysis results show, dispersal limitation (stochastic) and undominated processes significantly influenced the assembly of denitrifying microbial communities. This study broadened our understanding of the denitrifying bacterial community structure and its function on epiphytic biofilms in freshwater ecosystems with new information provided.Keywords：denitrifying bacteria;epiphytic biofilms;community assembly;null model7|0|2Updated：2023-05-20
Ecology
- Abstract：Archaea regulate the biogeochemical processes of ocean systems. The Changjiang (Yangtze) River estuary (CRE) is a complex and dynamic area strongly affected by seawaters and ocean currents. In this study, the planktonic archaeal communities in the surface and bottom seawaters of the CRE were investigated. Significant differences in the archaeal community composition were found between the surface and bottom seawaters (P < 0.001). Marine Group Ⅱ (MG-Ⅱ) was dominant in the surface layers, and Nitrosopumilales was enriched in the bottom layers. Marine Group Ⅲ (MG-Ⅲ) was more abundant in the bottom layers than in the surface ones (P < 0.001). These results were completely different from previous findings in the CRE seawater. Instead of dissolved oxygen (DO), temperature and salinity were the most vital environmental variations in the distribution of the archaeal communities. According to the predicted metabolic pathways, the following functional subcategories were enriched in the hypoxic condition: replication and repair, membrane transport, glycan biosynthesis and metabolism, amino acid metabolism, metabolism of cofactors and vitamins, and xenobiotics biodegradation and metabolism (P < 0.001), which indicated the strong adaptability of archaea to the harsh environment in the bottom seawater. These findings expand the understanding on archaeal structure and functions in the surface and bottom seawaters, including the hypoxic zones in the CRE, and may contribute to further works of the archaeal community in the CRE.Keywords：archaeal communities;adaptability;predicted metabolism;hypoxic zone;Changjiang River estuary6|0|0Updated：2023-05-20
- Abstract：Marine ecological disasters occurred frequently in recent years and raised widespread concerns about the ecological health of the ocean. We analyzed the spatiotemporal distributions of Ulva prolifera and Sargassum from April to July each year between 2016 and 2020 in the South Yellow Sea using multisource (GF-1 and HJ-1A/1B) remote sensing images, combined with the MODIS sea surface temperature (SST) data, photosynthetically active radiation (PAR) data, and Quick SCAT sea surface wind (SSW) data, to explore the potential influencing factors. The results show that (1) U. prolifera and Sargassum appeared mainly from May to July and April to June, respectively; (2) U. prolifera showed an impact in larger spatial scope than that of Sargassum. U. prolifera originated in the shoal area of northern Jiangsu and finally disappeared in the sea near Haiyang-Rongcheng area. The spatial scope of the impact of Sargassum tended to expand. Sargassum was first detected in the ocean northeast of the Changjiang (Yangtze) River estuary and disappeared near 35°N; and (3) correlation analysis showed that the SST influenced the growth rate of U. prolifera and Sargassum. PAR had varied effects on U. prolifera and Sargassum at different times. A moderate light conditions could accelerate the growth and reproduction of U. prolifera and Sargassum. High irradiance levels of ultraviolet radiation may cause photoinhibition and damage on U. prolifera and Sargassum. The southeast monsoon and surface currents promoted the drift of U. prolifera and Sargassum from the southeast to the northwest and north. Therefore, the spatial and temporal similarities and differences between U. prolifera and Sargassum were influenced by a combination of factors during their growth processes.Keywords：Ulva prolifera;Sargassum;virtual-baseline floating macro algae height (VB-FAH);spatiotemporal distribution;South Yellow Sea;multi-source remote sensing17|3|4Updated：2023-05-20
- Abstract：Information on the dietary composition and food preferences of the giant jellyfish Nemopilema nomurai is important for understanding the trophic drivers of jellyfish outbreaks and their ecological consequences. We used fatty acid (FA) and stable isotope (SI) biomarkers to analyze the diet of N. nomurai from the Yellow Sea in August 2016. N. nomurai was found at all sampling stations, with abundances ranging from 59 inds./km2 to 1 651 inds./km2. There were no significant differences between large (> 80 cm in diameter) and small (20–30 cm in diameter) medusae, either in FA compositions or in SI values, which suggests that large and small jellyfish have the same food composition and similar trophic levels. Compared to other zooplanktons, the relatively high levels of C20:4n-6 in total FAs (~12%) indicates that organic detritus contributes considerably to the food composition of the jellyfish. The mixed model Stable Isotope Analysis in R (SIAR) revealed that N. nomurai tended to prey on smaller organisms (< 1 000 μm in diameter) which comprised about 70% of its diet. This means the N. nomurai blooms will put high feeding pressure on the small plankton. The similar SI values and FA composition indicates that krill may share the same food resources with N. nomurai, which suggests that the jellyfish blooms may affect krill populations as a result of food competition.Keywords：Nemopilema nomurai;fatty acid;stable isotope;dietary preferences8|0|0Updated：2023-05-20
- Abstract：Periwinkle Littoraria sinensis is a widely distributed gastropod in rocky intertidal zone of the northwestern Pacific. To examine genetic diversity and genetic connectivity among coastal populations of L. sinensis in China, 1 636 pairs of primers were successfully designed using whole-genome shotgun sequencing, de novo assembly, and a bioinformatics pipeline QDD. Twelve highly variable polymorphic markers were selected to genotype 351 individuals from 15 populations. Data of nine microsatellite loci were retained for population genetic analysis, and weak genetic differentiation among populations were detected, suggesting high gene flow among populations. The long planktonic larval duration of L. sinensis might have played an important role in the high gene flow among populations. A tendency of genetic differentiation between north and south populations of L. sinensis was detected, which might be resulted from isolation due to lowered sea level in the last glacial maximum. Furthermore, the newly founded populations along the coast of Jiangsu Province were closely related to populations to the south of the Changjiang (Yangtze) River estuary, suggesting that the main source of the newly founded populations is from natural rocky populations south of the estuary.Keywords：population genetics;Littoraria sinensis;gastropod;simple-sequence repeats6|0|1Updated：2023-05-20
- Abstract：Herbivore digestion in aquatic ecosystems is usually considered a method of nutrient repackaging rather than recycling, as recalcitrant and low-level nutrients are presumed for their egesta. We hypothesize that this opinion holds only for nutrients recycled by excretion and egestion, not for those elements recycled overwhelmingly by fecal decomposition. In this study, we compared the dissolution of biogenic silica (BSi), phosphorus (P) and iron (Fe) between two food items and fecal pellets of two marine invertebrates fed on artificial seawaters free of bacteria. Relative to raw food materials, the mass proportion in fecal pellets of BSi increased, while that of P and Fe decreased. During the 21 days of incubation, the total dissolution rate of BSi was 13.9–36.0 times higher in fecal pellets than food items, followed by P (1.5–4.2 times) and Fe (1.1–2.4 times). While the dissolution of BSi and Fe occurred mostly in the first few days, P was mostly released in the last ten days. Regarding BSi dissolution, a higher rate was observed in oyster Crassostrea gigas than the Echiuran Urechis unicinctus, but no significant difference was found between fecal pellets in either species under naturally available diatom food (Phaeodactylum tricornutum) and introduced terrestrial food (rice husk powder), respectively. Our results show direct evidence of digestion-associated nutrients mobilization. BSi dissolution after animal digestion may be similarly efficient to that caused by bacteria colonization in natural seawater.Keywords：macroinvertebrate;nutrient regeneration;feces;mariculture;fecal silicate dissolution6|0|0Updated：2023-05-20
Continued from the back cover
- Abstract：Carnosine and its analogues are histidine-containing dipeptides (HCDs) playing diverse functions in vertebrates. However, the distribution and the metabolism of carnosine in invertebrates are still unknown. In this study, Mytilus coruscus, a shellfish with important economic value in China, was selected for the investigation of HCD content and the expression profiling of carnosine-related genes in various mussel tissues. Quantification of HCD by amino acids analyzer revealed a low concentration of anserine in muscular tissues in Mytilus, indicating the presence of HCD even in an invertebrate. mRNA expression of five carnosine metabolic-related genes was profiled in various tissues, and the results highlighted the relative higher expression level of these genes in muscular tissues. Considering the fact that beta-alanine supplementation can increase the HCD content in vertebrates, a beta-alanine injection was performed and the changes of HCD concentration and the mRNA expression of carnosine related genes were investigated in five mussel tissues. The results revealed the increase of HCD concentration, as well as the up-regulated expression level of related genes, in tested tissues of beta-alanine injected mussels. Transcriptomic analysis for the whole soft tissue of mussel before and after beta-alanine injection were performed, and 3 569 differential expression genes (DEGs) were identified in the beta-alanine injected group when compared to their expression levels in the control. These data indicated the complex effects of beta-alanine on M. coruscus metabolism, and those DEGs enriched in pathways of cancers, muscle contraction, and tyrosine metabolism highlighted the possible functions of beta-alanine in cell proliferation, sports, and melanogenesis, respectively.Keywords：Mytilus coruscus;beta-alanine;carnosine;histidine-containing dipeptides;transcriptome6|0|1Updated：2023-05-20
- Abstract：Inhibitory Smads (I-Smads), which belong to the Smad family and inhibit bone morphogenic protein 2 (BMP2) signaling by a variety of mechanisms, can suppress innate immunity responses in vertebrates. However, there are no reports for the role of Smad6 in immunity in mollusks. In this study, we showed that Smad6 of the pearl oyster Pinctada fucata martensii was located in the Smad6 cluster of the phylogenetic tree; mRNA expression of Smad6 and Smad3 was up-regulated after lipopolysaccharide and polyinosinic: polycytidylic challenge; and transcript levels of Smad6 and Smad3 showed opposite patterns during wound healing. Under salinity stress, water inflow and outflow in the gills appear to be regulated by BMP2-Smads signals, and BMP2-Smads signaling may be closely related to the immune response. Our results indicate that Smad6 is involved in immunity, that it plays a positive role in the response to immune challenge and an inhibitory role during wound healing, and that Smad6 and Smad3 may work against each other.Keywords：Smad6;BMP2-Smads signal pathway;expression;immunity;Pinctada fucata martensii6|0|0Updated：2023-05-20
- Abstract：The phosphatidylinositol (PI) signaling system,a central regulator of eukaryotic metabolism,is widely found in eukaryotes for regulating a variety of cell activities. Most of the genes in the PI signaling system were found conserved in Pyropia yezoensis. In this experiment,wortmannin was used as an inhibitor to inhibit the activity of phosphatidylinositol-3 kinase (PI3K),an important regulator of the PI signaling system. After wortmannin treatment,the mitotic division of P. yezoensis was significantly inhibited in a dose-dependent manner,and the mitotic division percentage was reduced by 68.1% and 91.9% in the 5-and 10-µmol/L groups,respectively. When thalli were treated with wortmannin,the levels of reactive oxygen species (ROS) were significantly decreased. Furthermore,the expression level of PI3K was inhibited and the expression levels of downstream genes regulated by PI3K was significantly changed. In the PI3K-AGC signaling pathway,the expression levels of Serine/threonine protein kinase (AGC) and cyclin-dependent kinases A (CDKA) were downregulated,while WEE1 kinase gene (WEE1) was upregulated. Three nicotinamide adenine dinucleotide phosphate (NADPH) oxidase genes were downregulated after wortmannin treatment. These results indicate that the PI signaling system plays an important role in the regulation of cell activity in P. yezoensis. It was speculated that the growth and development of P. yezoensis might be regulated by P. yezoensis PI3K,which promoted the expression of the AGC gene and further regulates the expression of downstream WEE1 and CDKA genes to advance mitotic division,and also promoted the expression level of NADPH oxidase that regulates ROS homeostasis.Keywords：Pyropia yezoensis;phosphatidylinositol signaling system;reactive oxygen species;mitotic division6|0|0Updated：2023-05-20
- Abstract：Hydroxypropyltrimethyl ammonium chloride chitosan (HACC) and hydroxypropyltrimethyl ammonium chloride fully deacetylated chitosan (De-HACC) were synthesized with various degrees of substitution by altering the ratio of chitosan to glycidyl trimethyl-ammonium chloride (GTMAC). The effects of the quaternary ammonium degree and the acetyl group of these polymers on immunostimulatory activities were detected in RAW 264.7 cells. The expression levels of nitrogen oxide (NO),interleukin-6 (IL-6) and tumor necrosis factor (TNF-α) were compared. Results show that the removal of acetyl groups in chitosan obviously improved the degree of substitution of quaternary ammonium salts. In addition,HACC and De-HACC were capable of promoting immunological activity in a substitution-dependent manner; HACC was positively correlated,and De-HACC was negatively correlated. Among tested ratios,HACC-30% and De-HACC-54% performed better than the others,and De-HACC-54% performed the best. Generally,quaternized chitosan possesses immunostimulatory activity,which is related to the degree of quaternization and the acetyl group.Keywords：quaternized chitosan;fully deacetylated quaternized chitosan;degree of quaternization;Immunostimulatory activity6|0|0Updated：2023-05-20
- Abstract：Some benthic Prorocentrum can produce okadaic acid (OA) and dinophysistoxins (DTXs) that cause diarrheic shellfish poisoning (DSP) in humans. The diversity and toxin profiles (OA and DTXs) of benthic Prorocentrum were investigated in the Xisha Islands,South China Sea. The benthic Prorocentrum was identified by both morphological features and molecular phylogenies. Morphologies were examined by light,fluorescence,and scanning electron microscopy,and phylogenetic analyses were based on partial large subunit (LSU) rDNA and ITS1-5.8S-ITS2 (ITS) region. Seven Prorocentrum species including P. borbonicum,P. caipirignum,P. concavum,P. elegans,P. cf. emarginatum,P. lima complex,and P. rhathymum were identified in Xisha Islands. Among them,P. borbonicum and P. elegans were recorded in Chinese waters for the first time. OA and DTXs contents of seven benthic Prorocentrum species were evaluated based on liquid chromatography-tandem mass spectrometry (LC-MS/MS). All Xisha Islands strains of P. lima complex produced OA at contents ranging from 1 663 to 3 816 fg/cell. P. caipirignum also generated OA at 407 fg/cell,but other five species had no detectable toxins. Besides,interestingly,two strains of P. lima complex produced DTX-1 only (74 and 183 fg/cell) and another two strains generated an isomer of OA and DTX-2. Our findings provided insight into the biodiversity of benthic Prorocentrum in the Xisha Islands and pointed out the potential risk of DSP in this area.Keywords：Prorocentrum;diversity;dinoflagellate;okadaic acid;dinophysistoxins;Xisha Islands6|0|1Updated：2023-05-20
- Abstract：Amphidinium species are amongst the most abundant benthic dinoflagellates in marine intertidal sandy ecosystems. Some of them are able to produce a variety of bioactive compounds that can have both harmful effects and pharmaceutical potentials. The diversity of Amphidinium in shallow waters along the Chinese coast was investigated by isolating single cells from sand,coral,and macroalgal samples collected from 2012 to 2020. Their morphologies were subjected to examination using light microscopy (LM) and scanning electron microscopy (SEM). A total of 74 Amphidinium strains were morphologically identified,belonging to 11 species: A. carterae,A. gibbosum,A. operculatum,A. massartii,A. cf. massartii,A. fijiensis,A. pseudomassartii,A. steinii,A. thermaeum,A. theodori,A. tomasii,as well as an undefined species. The last seven species have not been previously reported in Chinese waters. Amphidinium carterae subclades I,II,and IV were found in the South China Sea,while subclade III was only found in the Yellow Sea. Threadlike body scales were observed on the surface of subclades III and V,supporting the idea that A. carterae might contain several different species. Large subunit ribosomal RNA (LSU rRNA) sequences-based phylogeny revealed two groups (Groups I and II) within Amphidinium,which is consistent with the relative position of sulcus (in touch with cingulum or not). In addition,large differences in morphology and molecular phylogeny between A. operculatum (the type species of Amphidinium) and other species,suggest that a subdivision of Amphidinium might be needed. The pigment profiles of all available strains were analyzed by high performance liquid chromatography (HPLC). Eleven pigments,including peridinin,diadinoxanthin,diatoxanthin,pheophorbide (and pheophorbide a),antheraxanthin,β-carotene,and four different chlorophylls were detected. The high pheophorbide/pheophorbide a ratio in Amphidinium implies that it may be a good candidate as a natural source of photosensitizers,a well-known anticancer drug.Keywords：harmful algae;benthic-epiphytic dinoflagellate;phylogeny;geographic distribution;pheophorbide;photosensitizers7|0|0Updated：2023-05-20
- Abstract：A new monotypic diatom genus Chinia gen. nov. from estuarine mangrove habitats in Fujian, China is described. Light, scanning and transmission electron microscopy observations of its morphology show that this diatom differs from any established raphid diatom genus. The new genus is distinguished by a strongly undulate valve face, eccentric raphe canal, and perforated copulae. Its distinctly elevated and perforated raphe canal, classified as simonsenioid type, is supported by sparse infundibulum-like portulae, and the portulae are separated by large fenestrae. The valves of Chinia also have hymenate areolar occlusions and the raphe lacks a central nodule. However, unlike most Bacillariaceae with two plastids, including Simonsenia, Chinia has a single plastid similar to those in Entomoneis and Surirella. Despite the similarities to Simonsenia, Chinia features porous raphe canal and loose striation, which is different from those of Simonsenia that has a solid raphe canal and distinct rows of areolae. These distinctive cytological and morphological characters suggest an affinity of the new genus to the Bacillariaceae.Keywords：marine diatoms;East China Sea;taxonomy;Bacillariaceae;new genus;simonsenioid raphe6|0|0Updated：2023-05-20
- Abstract：Two cyanobacterial strains CHAB5870 and CHAB5871 morphologically identified as Nostoc-like species were isolated from different habitats in China, and they were phylogenetically and taxonomically characterized based on a polyphasic approach combining morphological, ecological, and molecular data. In the 16S rRNA gene phylogeny inferred using maximum likelihood, maximum-parismony, and bayesian inference methods, these two strains clustered within the Pseudoaliinostoc clade. The 16S rRNA gene sequences of these two strains displayed ≥95.5% and ≤98% similarity to Pseudoaliinostoc species, which indicated them to represent new species of the genus Pseudoaliinostoc. Furthermore, the unique pattern of D1-D1' and Box-B helix of the 16S-23S rRNA internal transcribed spacer (ITS) secondary structure also revealed that two strains represented novel species. These results supported the establishment of two new Pseudoaliinostoc species with the name P. jiangxiense sp. nov. and P. yunnanense sp. nov.Keywords：16S rRNA gene;16S-23S ITS;new species;morphology;polyphasic approach;taxonomy7|0|2Updated：2023-05-20
- Abstract：Species of the red algal order Acrochaetiales mostly inhabit marine environments, with only two freshwater taxa Audouinella and Ottia. A new genus and species are described for freshwater red alga Pauciramus yunnanensis from Ailao Mountain, Yunnan, China. It is closely related to Ottia and a new order Ottiales was proposed for these genera. Pauciramus has unique combination of morphological characteristics including the following: plants caespitose and densely pulvinate, slender uniseriate filaments with well-developed rhizoids, rarely branched, cylindrical vegetative cell with a single, ribbon-shaped and parietal chloroplast, reproduction by tetrasporangia, and dense sporangial branchlet only at the upper portion of filaments. Phylogenetic analysis of sequence data from the plastid ribulose-1, 5-bisphosphate carboxylase-oxygenase large-subunit (rbcL), small subunit gene of the ribosomal cistron (SSU) and barcode region near the 5' end of the mitochondrial cytochrome oxidase subunit I (COI-5P) indicated that: the new taxon, P. yunnanensis, was in a well-supported clade with Ottia meiospora, and this clade was sister to order Palmariales and Acrochaetiales. To adhere to the principle of monophyly, a new freshwater order Ottiales including Ottia and Pauciramus is proposed. Despite the high sequence interspecific divergences and obvious morphological differences between genera Ottia and Pauciramus, seems impractical to establish a new family for a monospecific genus. Therefore, we temporarily classified Pauciramus into the family Ottiaceae, and made necessary revisions to the description to accommodate this genus.Keywords：China;5' end of the mitochondrial cytochrome oxidase subunit I (COI-5P);Ottiales;Pauciramus;ribulose-1, 5-bisphosphate carboxylase-oxygenase large-subunit (rbcL);small subunit gene of the ribosomal cistron (SSU)8|0|0Updated：2023-05-20
- Abstract：The genus Rhynchospio has fronto-lateral horns on prostomium, paired branchiae from chaetiger 2 to near the posterior end, capillary notochaetae only, and more than two pairs of pygidial cirri. Rhynchospio species are common in coastal soft bottom communities; nevertheless, many recorded Rhynchospio specimens around the world are currently undescribed. Here we described a Rhynchospio species based on specimens collected from Qingdao, China. Comparison with the reported DNA sequences of four gene markers (16S rRNA, 18S rRNA, 28S rRNA, and Histone H3) and brief morphological description of specimens collected from Jinhae Bay, South Korea, previously reported as Rhynchospio aff. asiatica, indicated that they are conspecific. Morphologically, specimens of R. aff. asiatica from Qingdao are characterized by having neuropodial hooded hooks from chaetigers 14-17 (vs. 10-23 in R. asiatica) to near pygidial chaetigers, sperm from chaetiger 11 to 14 (vs. from chaetiger 11 to 21-22 in R.asiatica), oocytes from chaetigers 16-17 to 26-39 (vs. from 22-24 in R.asiatica), and 4-6 (vs. up to 6 in R. asiatica) pygidial cirri. Genetically, Rhynchospio aff. asiatica is most closely related to R. arenincola Hartman, 1936 from California, USA with the interspecific distances of 20.02% (16S rRNA), 4.50% (18S rRNA), 8.44% (28S rRNA), 2.74% (Histone H3), and 6.10% (concatenated sequences). Water flow across the dorsum created by ciliary beating of the branchiae and nototrochs, observed on live specimens, may help transport gametes from reproductive segments in anterior and middle parts to the posterior brooding segments. Phylogenetic trees based on concatenated sequences of four gene markers of 54 spioniform species in 25 genera revealed two clades, covering the two subfamilies Spioninae and Nerininae respectively. Two families (i.e., Poecilochaetidae and Trochochaetidae) in the order Spionida were clustered within Spionidae, supporting a morphology-based proposal that these families bearing a pair of prehensile, grooved palps should be grouped within a more broadly defined family Spionidae. Mapping morphological and reproductive characteristics to the phylogenetic trees indicated that the ancestor of spionids might lack branchiae, broadcast spawn thick-envelop oocytes and ect-aquasperm, and produce planktotrophic larvae.Keywords：Annelida;phylogeny;taxonomy;Yellow Sea6|0|1Updated：2023-05-20
Biology
- Abstract：The sound stimulus has a significant impact on marine animals. However, many studies have focused on the negative impacts of sound on marine vertebrates. The positive impacts of sound on marine animals, especially on marine invertebrates, were rarely studied. In the present study, we evaluated the effects of music on the survival and development of an economically important marine invertebrate, swimming crab Portunus trituberculatus. Three pieces of classical music and a control group, i.e., Eine Kleine Nachtmusik by Mozart (EK), Bach-Violin Concerto No. 1 (BV), Anonymous Romanza by Anonymous (AR), and environmental sound (EN) were used. The sound pressure received were 163-dB root mean square (RMS) re 1 μPa for EK, 166-dB RMS re 1 μPa for BV, 165-dB RMS re 1 μPa for AR, 44-dB RMS re 1 μPa for EN, respectively. The larvae were subject to 3-h classical music transmission every day during the entire larval development period. The result showed that BV and AR significantly elevated the cumulative survival rate of the larva from 3.42%±1.77% (EN) to 10.65%±1.69% (BV) and 7.12%±1.37% (AR) respectively (P < 0.05). Though music did not affect the cumulative development time of larvae from Zoea Ⅰ to Zoea Ⅳ, it significantly increased the molting rate of megalopa from 24.00%±11.78% (EN) to 44.00%±13.06% (AR) and 46.67%±10.50% (BV) (P < 0.05). Musical exposure during critical growth intervals may contribute to the survival and development of larval crustaceans. From an application point of view, music intervention is much economically feasible. The observed music effects imply that music could further enhance growth, welfare, and production.Keywords：swimming crab;Portunus trituberculatus;sound;classical music;oxygen consumption7|0|0Updated：2023-05-20
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Aquaculture and Fisheries
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