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Volume 41 ， Issue 3 ， 2023
- Abstract：Interannual variations of the eddy kinetic energy (EKE) related to two types of winter circulation events (“O” and “U”) were investigated based on the outputs of the Ocean General Circulation Model (OGCM) for the Earth Simulator (OFES) and the corresponding energetic analyses. Results show that the EKE is strong and extends eastward to offshore the Vietnam coast about 2°, associated with the weaker South China Sea western boundary current (SCSwbc) in “O” type years, while the EKE is weak and high value that can be attained is narrowed along the coast, associated with the stronger SCSwbc in “U” type years. The energy budget shows that the wind stress and barotropic/baroclinic instability are important factors to regulate the EKE in “U” and “O” years. For “U” years, under a strong winter monsoon forcing, the SCSwbc strengthen, the directly wind work and barotropic conversion from the mean kinetic energy (MKE) to EKE are weak, thus the EKE decrease corresponding to the baroclinic conversion from the kinetic energy to potential energy. However, the situation is reversed in “O” years. Under the influence of El Niño events, wind stress forces can weaken SCSwbc and enhance EKE in pattern “O”, whereas La Niña events have relatively weaker influences. The barotropic conversion rate in “O” type is nearly eight times of the “U” type. The pressure work and advection term are the main sources to greatly suppress EKE in the SCSwbc region.Keywords：two-type winter circulation;South China Sea western boundary current;energy budget12|0|0Updated：2024-10-12
- Abstract：To investigate the spatiotemporal variations in the mixed layer depth (MLD) in the Arctic basins, a new criterion to determine the MLD, called the improved maximum angle method (IMAM), was developed. A total of 45 123 potential density profiles collected using Ice-Tethered Profilers (ITPs) in the Arctic basins during 2005–2021 were used to demonstrate the method’s effectiveness. By comparing the results obtained by the fixed threshold method (FTM), percentage threshold method (PTM), and maximum gradient method (MGM) for profiles in the Canada Basin, Makarov Basin, and Eurasian Basin, we determined that the quality index (1.0 for perfect identification of the MLD) of the IMAM regarding the assessment of the MLD determination method reached 0.94, which is much greater than those of other criteria. Moreover, two types of the density profiles were identified based on the mixed layer development stage. The MLDs of the typical profiles determined using the IMAM were found to have better consistency with the original definition. By utilizing the new mixed layer criterion, the seasonal variations and regional differences in the MLD in the Arctic basins were analyzed. Spatially, the summer and winter MLDs in the Canada Basin were the shallowest (13.55 m in summer, 26.76 m in winter) than those in the Makarov (29.51 m in summer, 49.08 m in winter) and Eurasian (20.36 m in summer, 46.81 m in winter) basins due to the stable stratification in the upper ocean and the subsequent small effects of dynamic and thermodynamic processes (wind-driven stirring and brine rejection) in the Canada Basin. Seasonally, in the three Arctic basins, the average MLD was shallowest (22.77 m) in summer; it deepened through autumn and reached a winter maximum (41.12 m).Keywords：mixed layer depth (MLD);improved maximum angle method (IMAM);Arctic basins12|0|0Updated：2024-10-12
- Abstract：The unavoidable nature of Ulva prolifera mixed pixel in low-resolution remote sensing images would result in rough boundary of U. prolifera patches, omission of tiny patches, and overestimation of coverage area. The decomposition of U. prolifera mixed pixel addresses the issue of coverage area overestimation, and the remaining problems can be alleviated by subpixel mapping (SPM). Due to the drift and dissipation of U. prolifera, a suitable SPM method is the single image-based unsupervised method. However, the method has difficulties in detail reconstruction, insufficient learning of spectral information, and SPM error introduced by abundance deviation. Therefore, we proposed a multiple-feature decision fusion SPM (MFDFSPM) method. It involves three branches to obtain the spatial, abundance, and spectral features of U. prolifera while considers multi-feature information using the fusion strategy. Experiments on the Geostationary Ocean Color Imager images in the Yellow Sea of China indicate that the MFDFSPM overperforms several typical U. prolifera SPM methods in higher accuracy and stronger robustness in both SPM and abundance calculation, which produced subpixel map with more detailed spatial information and less noise.Keywords：Ulva prolifera;subpixel mapping;multiple-feature decision fusion;abundance;geostationary ocean color imager (GOCI)19|0|0Updated：2024-10-12
Physics
- Abstract：Submarine canyon-channel systems have been documented in the Parece Vela Basin, West Mariana Ridge; however, the mechanism of the formation and controlling factors remain poorly understood. Based on high-resolution multibeam bathymetric data and two-dimensional (2D) seismic profiles, we identified and mapped the submarine canyon-channel system along the middle segment of West Mariana Ridge in the Philippine Sea. These submarine canyon-channels show a main W-E orientation at depth of 2 000–4 500 m. They are approximately 72–128 km in length and 1.3–15 km in width, and their canyon heads are adjacent to the seamounts with several branches. The upper reaches of submarine canyon-channels are characterized by deeply incised, narrow, V-shaped thalwegs, suggesting the powerful erosion of gravity flows. The distinguished sediment waves are suggested to be resulted from the interaction of turbidity currents and seafloor. Our observations demonstrate that gravity flows originated from the collapses of seamount flanks plays a vital role in developing the submarine canyon-channel system along the West Mariana Ridge. This work provides better understanding of erosion, transport, and deposition of sediments from subducting ridges to deep-water basins, and also new insights into the origin and evolution of submarine canyon-channel systems along subducting ridges.Keywords：submarine canyon-channel system;gravity flow;subducting ridges;West Mariana Ridge9|0|0Updated：2024-10-12
- Abstract：Clay minerals are usually considered as important indicators to identify sources in both terrigenous and marine sediments. In particular, clay minerals in metalliferous sediments (MS) have long been studied in global oceans except in South Mid-Atlantic Ridge (SMAR) due to limited explorations. Thus, 32 MS and 34 non-MS (NMS) samples were analyzed to clarify the distribution characteristics and mineral compositions of clay minerals. All the sediments were collected along the SMAR between 12°S and 27°S. After removal of organic matter and carbonate, clay fractions (<2 μm) were investigated by X-ray diffraction (XRD) analysis. Results show that clay mineral assemblages of surface MS consist dominantly of smectite, less abundant illite, chlorite, and kaolinite in average weight percentage of 30%, 21%, 18%, and 16%, respectively. On the other hand, clay mineral assemblages in the NMS consist mainly of illite, less abundant kaolinite, chlorite, and very scarce smectite in average weight percentage of 47%, 29%, 24%, and 0.2%, respectively. The clay fractions in MS are mainly composed of amorphous or poorly crystallized Fe/Mn oxyhydroxides, clay mineral, quartz, and plagioclase. However, the counterparts in the NMS are mainly composed of well-crystallized clay minerals, quartz, and plagioclase without the presence of Fe/Mn oxyhydroxides. It is suggested that most of the illite, kaolinite, and chlorite in both MS and NMS are likely aeolian dust in origin from South Africa continent. In addition, the abundance of kaolinite dominates the clay mineral assemblage at low latitudes, where the intensive chemical weathering of continental source rocks facilitating the formation of kaolinite. In terms of smectite, it is indicated of authigenic origin in consideration of only smectite is available in several MS and the absence in NMS. Moreover, the MS samples with only smectite available are always accompanied by goethite. Therefore, it is assumed that most of smectite occurred in studied area is the results of interaction between hydrothermal Fe-oxyhydroxide, silica, and seawater.Keywords：metalliferous sediment;South Mid-Atlantic Ridge (SMAR);clay mineral;smectite8|0|1Updated：2024-10-12
- Abstract：The Bohai Sea is influenced by numerous extreme oceanic wave events in history. However, it is often difficult to determine the types of these events due to the lack of detailed historical records, causing uncertainty in the reconstruction of historical coastal disasters. We investigated an anomalous sand layer in the Xiliyu Village by the coast of Laizhou Bay, Shandong, from which an extreme event deposit was identified using a multi-proxy approach including grain size distribution, geochemistry, and magnetic susceptibility. This event was dated 2 700–3 100 a bp, and caused inundation of a large coastal area of Laizhou Bay. By comparing historical records with instrumental data, we believe that the event deposit was generated by a severe storm surge with wind speed of >34.9 m/s.Keywords：event layer;storm surge deposit;multiple proxy analysis;winter storms;Laizhou Bay8|0|0Updated：2024-10-12
- Abstract：The quantitative analysis of sediment sources in a sink is an important scientific topic and challenge in provenance research. The characteristics of heavy minerals, combined with the geochemical constituents of detrital grains, provide a reliable provenance-tracing approach. We developed a mineral identification method to analyze the multiple grain-size fraction of sediments, from which the elemental geochemistry of hornblende was used to compare the characteristics of sediments from the Huaihe River and Huanghe (Yellow) River in eastern China. Elements that were statistically identified as being able to discriminate sediment provenance were employed to perform a quantitative analysis of the sources of sediments of the abandoned Huanghe River. Results reveal that the Huaihe River is characterized by a high amphibole content of >60% and that the Huanghe and abandoned Huanghe rivers have greater abundances of limonite and carbonate minerals compared with those of the Huaihe River. The contents of trace elements and rare earth elements in hornblende show that the sediments of the abandoned Huanghe River are similar to those of the Huanghe River but different from those of the Huaihe River. Furthermore, chemical mass balance was used to calculate the relative contributions of different provenances of sediment from the abandoned Huanghe River, and nine trace elements of hornblende were identified as discriminators of provenance. Approximately 2% of the hornblende in the abandoned Huanghe River is derived from the Huaihe River and 98% from the Huanghe River. Considering the proportion of hornblende in the total sediment, it is inferred that the contribution of Huaihe River sediment to the abandoned Huanghe River is approximately 0.5%. This study shows that mineral analysis using multiple grain-size fractions (within the wide range of 1Φ to 6Φ) with assessment in elemental geochemistry of hornblende can characterize the provenance of fluvial material in coastal zones.Keywords：quantitative provenance analysis;heavy mineral;multiple grain-size fraction;hornblende;elemental geochemistry;fluvial sediment;the abandoned Huanghe River12|0|1Updated：2024-10-12
- Abstract：Geochemical behaviors of heavy metals are closely related to their chemical state that can be divided by sequential extraction into exchangeable (F1), bound to carbonates (F2), bound to Fe-Mn oxides (F3), bound to organic matter or sulfide (F4), and residual (F5). Uranium in sediment of the Huanghe (Yellow) River, China, in different chemical states was extracted using the five-step procedure of Tessier and the source and sink were analyzed. Results show that more than 70% of the total uranium was immobile residual F5 in abundance, followed in order of F4>F3>F2>F1, indicating that the main source of uranium in the sediments was from weathered rock in the drainage basin. In addition, the uranium in the sediments presents potential exogenous input in the Lanzhou, Baotou, and Tongguan reach. Fe-Mn oxides are main carriers of unstable uranium, especially those of F1 and F3. Calcite and illite are secondary adsorption minerals of unstable uranium in sediments under natural conditions. Human activities can also produce an obvious impact on uranium speciation. This study provides a reference for the application of sequential extraction in analyzing the source and sink of uranium in river sediments.Keywords：uranium;sequential extraction;mineral composition;sediment;Huanghe (Yellow) River9|0|0Updated：2024-10-12
- Abstract：Gas hydrates have been found in the western continental margin of South China Sea, which are revealed by widespread bottom simulating reflectors (BSRs) imaged from a three-dimensional (3D) seismic volume near the Guangle carbonate platform in the western South China Sea. Fluid-escape structures (faults and gas chimneys) are originated below BSR were distinguished. A comprehensive model in three-level structure was proposed to depict the gas hydrate accumulation in the study area. In Level 1, regional major faults and gas chimneys provide the first pathways of upward migration of gas near basement. In Level 2, pervasive polygonal faults in carbonate layer promote the migration of gas. In Level 3, gases sourced from near-basement accumulate within shallow sediment layers and form gas hydrate above the unit with faults once appropriate temperature and pressure occur. The gas hydrates in the study area are mainly in microbial origin, and their accumulation occurs only when fluid-escape structures align in all the three levels. The proposed model of the gas hydrate accumulation in western SCS margin provides new insights for further studies in this poorly studied area.Keywords：gas hydrate;fluid-escape structures;gas sources;bottom simulating reflector (BSR);South China Sea12|0|0Updated：2024-10-12
Geology
- Abstract：Regime shifts from submersed macrophyte dominance to phytoplankton dominance have been widely reported in small- to medium-sized shallow lakes. However, alternative stable states in large shallow lakes (surface area >500 km2) remain unconfirmed. To understand the alternative stable states and the main influencing factors of submersed macrophytes in large lakes, the ecosystem states from monitoring data from 1959 to 2019 in large shallow Taihu Lake (2 338 km2 in average depth of 2.12 m) in China were examined. Changes in submersed macrophyte coverage (CMac) and phytoplankton chlorophyll a (Chl a) in the time series and their relationships with environmental factors were analyzed. During the field investigation from August 2018 to May 2019, nutrients and Chl a showed obvious heterogeneity across the lake, being generally higher in the western and northern areas and lower in the southeast area, while CMac was only observed in the eastern areas, e.g., East Taihu Lake, Xukou Bay, and Gonghu Bay. During the long-term monitoring from 1959 to 2019 in the Central Region, Meiliang Bay, and East Taihu Lake, Chl a increased significantly in the time series. CMac varied slightly among different subareas, always at low levels (<10%) in the Central Region and Meiliang Bay but at relatively high levels in East Taihu Lake (10%–90%). Frequency distributions of response variables had no multimodality except for CMac in East Taihu Lake, with two peaks between 15% and 20% and between 55% and 60%. A dual relationship was found between Chl a and total phosphorus (TP) in the areas with and without macrophytes, while CMac showed no relationship with TP, and submersed macrophytes did not flourish in the Central Region and Meiliang Bay even when TP was at very low levels (≈10 mg/m3). Taihu Lake had similar algal turbidity (TurbAlg) as small- to medium-sized lakes but generally presented with higher values of nonalgal turbidity (TurbNonAlg), as did their contribution to total turbidity as a percentage. This study suggested that large shallow Taihu Lake may have no alternative stable states, but more evidence is needed for East Taihu Lake, which was dominated by macrophytes, as it remains unknown whether hysteresis occurs between the processes of eutrophication and oligotrophication. Unfavorable conditions caused by wind might be the main reason due to the absence of submersed macrophytes in Taihu Lake. These results demonstrate that stricter nutrient control is needed to maintain a healthy state or to recover from a decayed state for large lakes.Keywords：alternative stable state;submersed macrophyte;phytoplankton;Taihu Lake;large shallow lake8|0|2Updated：2024-10-12
- Abstract：Batrachospermaceae is an important group of freshwater red algae. Available data of the latitude, longitude, and environmental factors on Batrachospermaceae distribution in Asia were analyzed to understand the geographical distribution of Batrachospermaceae genera in Asia. Statistical analyses, including one-way ANOVA, correlation analysis, stepwise regression analysis, principal component analysis, and linear discriminant analysis were conducted to characterize variation in geographical distribution and growth environment. Results reveal high variation in geographical distribution and growth environment among different Batrachospermaceae genera in Asia. Specifically, correlations between latitude and all environmental factors exclusive of altitude are significant, and longitude is significantly correlated with all environmental factors except for average relative humidity. The geographical distribution and growth environment of different Batrachospermaceae genera significantly differed. Altitude, maximum temperature, average temperature, minimum temperature, average relative humidity, average wind speed, maximum wind speed, and atmospheric pressure all contributed to explaining differences in the geographical distribution of Batrachospermaceae genera. Combining the results of correlation analysis, stepwise regression analysis, and principal component analysis, all environmental factors contributed to the different geographical distribution of Batrachospermum, Paludicola, Sheathia, Sirodotia, and Remainder (the rest), all environmental factors but atmospheric pressure contributed to the different geographical distribution of Kumanoa, and all environmental factors but average wind speed and maximum wind speed contributed to the different geographical distribution of Virescentia. However, the correlation between these significantly related environmental factors and taxa is not necessarily causative, and many other environmental factors, such as temperature, pH, conductivity, shading, current velocity, dissolved oxygen, hardness, substrata types, and nutrients etc., are likely to have an important impact on the geographical distribution of taxa, which is an important topic for future research.Keywords：Batrachospermaceae;biostatistics;environmental factor;geographical distribution;metrology10|0|0Updated：2024-10-12
- Abstract：Dam construction has a critical effect on river ecosystems in the world, resulting in a rapid decline in biodiversity and ecosystem health. However, the effect of dam construction on the assemblage pattern of benthic diatoms remains unclear. The benthic diatoms assemblages in the tributary backwater area of the Three Gorges Reservoir (TGR) were investigated under low water level (LWL) and high water level (HWL) conditions. Results show that Discostella stelligera, Nitzschia palea, and Craticula subminuscula were dominant species in LWL, while Achnanthidium minutissimum and Nitzschia dissipata were dominant in HWL. Furthermore, environmental variables, productivity parameters, diversity indices, and community similarity were found significantly different between LWL and HWL periods. The Mantel test indicated that both environmental and spatial factors had significant effects on diatom communities in backwater area, while productivity was also a key driving force in LWL. The variation partitioning analysis (VPA) further demonstrated that environment factors could explain the largest variance of diatom assemblages in HWL (9%) and LWL (11%), followed by spatial factors. The relative importance of productivity to diatom community was significantly enhanced in LWL, but only a slight effect was found in HWL. These results indicate that the diatom assemblages were shaped by both environmental filtering and spatial factors. The relative importance of spatial factors depended on the degree of productivity. Therefore, the homogenization of diatom communities due to environmental disturbance, e.g. eutrophication and dam building, is the underlying mechanism in assembling the benthic diatoms.Keywords：Three Gorges Reservoir;benthic diatom;assemblage;environmental heterogeneity;productivity6|0|0Updated：2024-10-12
- Abstract：Zooplankton are important linkages in the food web and can respond nonlinearly to environmental changes. Marine organisms thrive from spring to summer. Thus, it is crucial to understand how ecological functions of zooplankton communities may shift under seasonal environmental changes during this period. Samples were collected from May to August (May, June-I, June-Ⅱ, July-Ⅰ, July-Ⅱ, and August) in 2018 in Haizhou Bay, Jiangsu, East China for zooplankton and environmental variables. Crustaceans accounted for 75 out of 134 zooplankton taxa and 91.8% of total zooplankton abundance. The average abundance of crustacean varied between 2 824.6±635.4 inds./m3 in July-Ⅱ and 6 502.7±1 008.8 inds./m3 in June-Ⅱ. Multivariate analyses results showed that the dissimilarity of community increased gradually in the time series. Body length, feeding type, trophic group, and reproduction mode were used to investigate crustacean community functions. Trait-based functional groups contained species with similar ecological roles. Functional diversity fused the differences of species and trait. The proportion of large-sized species(2–5 mm) decreased with the increasing proportion of medium-sized species (1–2 mm). The proportion of current feeders increased with the drop in the proportion of mixed feeders. Parthenogenesis species increased with decreasing free spawners, and omnivores-carnivores increased with decreasing omnivores-herbivores. Generalized additive models suggested that temperature was the main driver of variations in crustacean zooplankton function. Seven identified functional groups varied with increasing temperature. Omnivorous-herbivorous copepods declined (90.0%–68.0%), whereas the parthenogenetic cladocerans increased (0–24.1%). The small egg-brooding ambush copepods fluctuated (6.5%–9.3%) with increasing water temperature. The other functional groups changed slightly. Functional diversity also varied according to temperature changes. The community structure and ecological function of crustacean zooplankton community showed gradual changes with increasing temperature from spring to summer.Keywords：zooplankton;trait;functional group;diversity;Yellow Sea;Haizhou Bay6|0|0Updated：2024-10-12
- Abstract：To identify the distribution pattern of macrofaunal assemblages of the Dafeng intertidal flats in response to hydrodynamic and sediment dynamic processes in the northern Jiangsu coast, East China, macrofauna sampling and hydrodynamic observations were carried out simultaneously across the mud flat, mixed mud-sand flat, and silt-sand flat of the intertidal zone in June 2018. Results show that there was a clear zonal distribution pattern of the macrofaunal communities, as is controlled by local hydrological and sedimentary environments. Principal component analysis (PCA) revealed three types of intertidal area in terms of hydrological and surficial sediment parameters. Similarly, three distinct groups of the macrofaunal communities, i.e., mud flat, mix mud-sand, and silt-sand groups, were recognized at similarity level of 24% based on the CLUSTER analysis in similarity profile (SIMPROF) test. Correlation analysis upon best variables stepwise search (BVSTEP) indicated the importance of the hydrodynamics (e.g., water temperature and salinity, tidal duration, flow speed, suspended sediment concentration, and wave height) in the differentiation of macrofaunal communities with different taxonomic classes over the intertidal zone. Therefore, macrofaunal assemblages, similar to hydrology and surficial sediment, have a unique zonation pattern. Small-sized deposit feeders adapt better to low energy environments, thus dominated the upper part of the intertidal flat, whilst the heavy and large-sized filter feeders and deposit feeders were dominant over the middle and lower parts. The hydrodynamic and sediment processes cause biota-niche separation, which affected the biological processes across the intertidal flat.Keywords：macrofaunal communities;hydrodynamic process;inter-tidal ecosystem;sedimentation;tidal flat;Jiangsu coast9|0|1Updated：2024-10-12
- Abstract：Euphausia superba and Thysanoessa macrura are dominant krill species in the Southern Ocean and their habitats are often overlapped reportedly. Studies of the feeding strategies of these two krill species will help us better understand the coexistence mechanisms and estimate the roles that krill played in the food web of the Southern Ocean. The trophodynamics of E. superba and T. macrura at different ontogenetic stages (furcilia, juvenile, adult) were studied using fatty acid and stable isotope biomarkers in the samples collected in Amundsen Sea during austral summer of 2017/2018 and 2018/2019. Diatoms like Fragilariopsis spp. was the most abundant phytoplankton species in the summer of 2017/2018, while the abundance of phytoplankton in the summer of 2018/2019 was dominated by Phaeocystis sp. The gradual increase of the carnivorous index 18꞉1n-9/18꞉1n-7 with ontogeny of both species in 2018/2019 indicated more carnivorous feeding of adults compared with juveniles and larvae. Meanwhile, greater δ15N values of T. macrura than that of E. superba were more significant in the juvenile and adult stages during the summer of 2018/2019. Our results indicate that the trophic niche differentiation between the two krill species appeared in postlarval stage and can be influenced by food availability. Compared with E. superba, T. macrura was more prone to feed omnivorously or carnivorously responding to food availability.Keywords：Antarctic krill;feeding strategies;fatty acids;stable isotopes;trophodynamics;Southern Ocean8|0|0Updated：2024-10-12
Ecology
- Abstract：Copepoda are one of the most significant animal groups present in aquatic ecosystems. Ecologists, evolutionary biologists, and biotechnologists continue to test new methods to study the application of Copepoda as model organisms in various fields of pure and applied science, from evolution and ecology to aquaculture as live feed, as biological control of mosquito larvae, as biological indicators of water and sediment quality, in environmental monitoring and as a source of protein in the food industry. This paper reviews the current progress and trends within copepod research from a number of different perspectives. We emphasize the importance of Copepoda and the necessity of strengthening research on various topics related to copepod biology, some of which are of great significance to local sustainable development.Keywords：bioindicators;aquaculture;pollutants;eutrophication;nutrition;halotolerance10|0|0Updated：2024-10-12
- Abstract：Yellowfin seabream Acanthopagrus latus is an important economic fish in Chinese coastal areas. Given its narrow distribution and overfishing, the genetic diversity of yellowfin seabream has been restricted for artificial breeding and reproduction. We performed full-length transcriptome sequencing and assembly of the genome of yellowfin seabream. A total of 68 086 unigenes were obtained, with an N50 of 3 391 bp on average length of 2 933 bp. A total number of 50 593 expressed sequence tags linked to simple sequence repeats (EST-SSR) were identified, among them dinucleotide repeats (40.6%) and AC/GT motifs (38.5%) were the most frequent. Of the 190 EST-SSRs for which PCR primer pairs were designed, 150 primer pairs successfully amplified target loci and 15 SSRs showed high polymorphism. The alleles per locus ranged 6–50 on average of 25.3. The expected and observed heterozygosity varied from 0.632 to 0.969 and from 0.519 to 0.953, respectively. The polymorphic index content (PIC) values of each locus ranged 0.587–0.966 on average of 0.851. Among six yellowfin seabream population samples preliminarily tested for genetic diversity and differentiation, the Fangchenggang (FCG) population in Guangxi Province had the highest mean observed heterozygosity (Ho) value (0.786), whereas the Zhangzhou (ZZ) population in Fujian Province had the lowest (0.678). The pairwise fixation index (Fst) values indicated significant population differentiation among six yellowfin seabream populations. This study provided evidence for the usefulness of the transcriptomic resource information and EST-SSR markers for natural resource conservation, population genetics, and breeding studies of yellowfin seabream in South China.Keywords：yellowfin seabream Acanthopagrus latus;full-length transcriptome;expressed sequence tags linked to simple sequence repeats (EST-SSR) marker;genetic diversity8|0|1Updated：2024-10-12
- Abstract：Leopard coral groupers (Plectropomus leopardus), commercially bred in South China, are a significant economical fish species. In this study, by means of quantitative real-time PCR (qRT-PCR) technology, we assessed the stability of six common reference genes expression and selected the appropriate reference genes in leopard coral groupers with or without Vibrio harveyi stimulation at different time points. These data produced by qRT-PCR was handled via the geNorm, NormFinder, and BestKeeper software. The results revealed all the examined reference genes had manifest tissue-specific expression in different tissues. Prior to V. harveyi stimulation, RPL13 gene was the appropriate reference gene among eleven tissue types (blood, spleen, hepatopancreas, kidney, stomach, gill, heart, skin, muscle, intestine, brain) in leopard coral groupers. Under V. harveyi stimulation, the most reliable reference genes varied from tissue to tissue and were closely hinged upon different time points. At 6-h post-bacterial injection, the appropriate reference genes in hepatopancreas, spleen, kidney, and gill were Actin, B2M, UBCE, and Actin, respectively. At 9- and 12-h post-bacterial injection, the appropriate reference genes in hepatopancreas, spleen, kidney, and gill were RPL13, Actin, Actin, and Actin, respectively. If one reference gene was preferable, RPL13, Actin, Actin, and Actin could be selected as the reference gene in hepatopancreas, spleen, kidney, and gill of leopard coral groupers after V. harveyi infection, respectively. Expression profiles of two target genes (IL-6 and NK-lysin) were used to further validate reliability of these selected appropriate candidates. This study will lay a solid foundation for the future research on qRT-PCR analysis of gene expression in leopard coral groupers.Keywords：Plectropomus leopardus;reference genes;Vibrio harveyi stimulation10|0|0Updated：2024-10-12
- Abstract：Acidic digestion is an important digestive process of marine fish. In fish stomach, two enzymes are involved in the secretion of hydrochloric acid (HCl) and proteomic digestion: H+/K+-ATPase and pepsinogen. However, the starting of digestive function in fish is still unclear. To reveal the details of acidic digestion of turbot Scophthalmus maximus in early development, a 40 day of turbot larvae culture was conducted. The H+/K+-ATPase gene from the turbot S. maximus (smH+/K+-ATPase) was identified and characterized. Based on our previous discription on pepsinogen of turbot S. maximus, we combined pepsinogen and H+/K+-ATPase and analyzed the mechanism of acidic digestion in turbot. Results show that the spatial and temporal expression profiles of H+/K+-ATPase agreed with pepsinogen A and C in turbot, indicating a synergetic action between H+/K+-ATPase and pepsinogen during the acidic digestion process. In addition, the turbot juveniles showed a faster growth after the expressions of H+/K+-ATPase gene and pepsinogen gene, demonstrating that pepsin had a higher digestive efficiency, for which a compound diet should be provided to the fish from Day 22 onward. This study provided a reference for biology research and aquaculture of turbot and other marine fishes.Keywords：turbot;Scophthalmus maximus;acidic digestion;H+/K+-ATPase;pepsinogen8|0|0Updated：2024-10-12
- Abstract：Caspase-8, first classified as a pro-apoptotic caspase, is considered to have arisen from duplication with caspase-10 and involves multiple immune and inflammatory responses in mammals. However, few are known on the phylogeny and function of caspase-8 in molluscs, one of the largest phyla in marine invertebrates. In this study, we conducted phylogenetic and functional analysis on molluscan caspase-8-like genes. Results indicate that duplication occurred in molluscan caspase-8-like genes, resulting in at least two caspase-8 copies in some groups of bivalves. Additional studies in Pacific oyster Crassostrea gigas showed different spatio-temporal expression patterns and subcellular localizations of CgCaspase-8-1 and CgCaspase-8-2. While no interaction was observed between CgCaspase-8-2 and CgFADD, the adaptor molecule in apoptosis, yeast two-hybrid and co-immunoprecipitation assays suggested the interaction between CgCaspase-8-1 and CgFADD, indicating its pro-apoptotic function. In addition, CgCaspase-8-1 showed interaction with the CARD domain of CgRIG-I. Together with two NF-κB subunits (Cgp105 and CgRel), their transcripts were up-regulated in response to poly(I:C) stimuli, supporting the immune function of both pro- and anti-inflammation. The results provide insight into the evolution and functional diversification of Bivalvia caspase-8 genes.Keywords：caspase-8;apoptosis;metamorphosis;inflammation;Crassostrea gigas10|0|1Updated：2024-10-12
- Abstract：As “Bohai Red” scallops were originated from the hybrids between the Peruvian scallop (Argopecten purpuratus) and the bay scallop (Argopecten irradians) northern subspecies (Argopecten irradians irradians). Twelve Wnt members were identified from the two subspecies of bay scallop, and 13 Wnt genes were found in the genome of the Peruvian scallop. Protein structure analyses showed that most Wnt genes poses all 5 conserved motifs except Wnt1, Wnt2, Wnt6, and Wnt9 in the bay scallops and Wnt2 and Wnt9 in the Peruvian scallop. Unexpectedly, Wnt8 gene was present while Wnt3 was absent in both the bay scallops and the Peruvian scallop. Phylogenetic analysis revealed that Wnt3 might have disappeared in the early evolution of mollusks. The expression profile of Wnt genes in the “Bohai Red” exposed to different temperatures was examined by qRT-PCR. Results show that expression of Wnt genes responded differentially to temperature changes. The Wnt genes such as Wnt1, Wnt6, Wnt7, Wnt11, and WntA that responded slowly to low and high temperature stresses may be related to the maintenance of basic homeostasis. Other Wnt genes such as Wnt4, Wnt9, Wnt5, and Wnt2 that responded rapidly to low temperature may play an important role in organismal protection against low temperature stress. And yet some Wnt genes including Wnt10, Wnt16, and Wnt8 that responded quickly to high temperature stress may play key roles in response to high temperature stress. The results provide new insights into the evolution and function of Wnt genes in bivalves and eventually benefit culture of “Bohai Red” scallops.Keywords：Peruvian scallop;bay scallop;"Bohai Red" scallops;Wnt gene;Temperature change;qRT-PCR8|0|0Updated：2024-10-12
- Abstract：Three polyamines (PAs) (spermidine (Spd), spermine (Spm), and putrescine (Put)) were used as growth regulators to the marine macroalgae Gracilariopsis lemaneiformis and to female gametophyte and reproductive tissues (cystocarps were constructed), which led to early maturation of cystocarps and spore release. Laboratory cultivation revealed that exogenous PA application accelerated the development of cystocarps, and the mean sporeling growth rate was 20%–50%/d during the initial week of cultivation. The spore count (SC), survival rate (SR), and germination rate (GR) of G. lemaneiformis showed different responses to PA (10-6 mol/L and 10-3 mol/L) treatments under different temperatures (18, 26, and 34 °C), light intensities (30, 60, and 90 µmol photons/(m2·s)), salinities (25, 30, and 35), and nutrient levels (25꞉2.5, 50꞉5.0, and 75꞉7.5 µmol/L NH4Cl꞉K2HPO4), and the optimal conditions were 26 °C, light intensity of 60 µmol/(m2·s), salinity of 35, and nutrient level of 50꞉5.0 µmol/L NH4Cl꞉K2HPO4. Under the optimum conditions, the SC per cystocarp increased by 82.38%, and the spore SR and GR increased by 33.07% and 46.44%, respectively. Each experiment lasted for 7 days, with the highest SC on Day 4 and plateauing on Day 7. The results indicate that PAs could promote the early maturation, spore release, survival, and germination of G. lemaneiformis under laboratory conditions.Keywords：Gracilariopsis lemaneiformis;polyamines;carpospores;spore release;survival rate;germination rate9|0|0Updated：2024-10-12
- Abstract：A new chloro-azaphilone derivative chaetoviridin L (1) along with four known analogues, namely, chaetomugilin A (2), chaetoviridin E (3), chaetomugilin O (4), and chaephilone D (5), is isolated and identified from the culture extract of Chaetomium globosum YP-106, a deep-sea derived fungus obtained from the hadal zone seawater collected in the Yap Trench. Their structures were determined based on detailed interpretation of nuclear magnetic resonance (NMR) spectroscopic, mass spectrometry (MS) data analysis and comparison with the reported literature. The absolute configuration of the new compound was established by quantum chemical calculations of electronic circular dichroism (ECD). All the isolated compounds were evaluated for pro-angiogenesis activity using zebra fish model. Compounds 1, 2, and 5 significantly promoted the angiogenesis in a dose-dependent manner and thus, these compounds might be used as promising molecules for the treatment of cardiovascular disease.Keywords：marine natural products;marine-derived fungi;azaphilones;hadal trench;deep-sea;Chaetomium globosum;pro-angiogenesis activity6|0|1Updated：2024-10-12
- Abstract：A new prenylated indole alkaloid 11,17-epi-mangrovamide A (1), a new natural occurring product, 1,7-dihydroxy-6-methyl-8-hydroxymethyl-xanthone (2), two known alkaloids, mangrovamide A (3) and mangrovamide G (4), and four known polyketide derivatives (5–8) were isolated and identified from the cold-seep sediment derived fungal strain Talaromyces funiculosus SD-523. Their structures were elucidated by combination of nuclear magnetic resonance (NMR), high resolution electrospray ionization mass spectroscopy (HRESIMS), quantum chemical electronic circular dichroism (ECD), and DP4+ probability analysis as well as by comparison of the data with literature reports. All isolated compounds were tested for antibacterial activities.Keywords：Talaromyces funiculosus;cold seep;prenylated indole alkaloid;antimicrobial activity12|0|0Updated：2024-10-12
- Abstract：This chemical study reports a novel siderophore-like compound, β-cyclopiazonic acid (1, β-CPA) extracted from marine fungus Aspergillus flavus. The chemical structure of β-CPA was elucidated by a combination of extensive spectroscopic analyses and TDDFT-ECD calculations. The iron-binding ability and CAS assays demonstrate that β-CPA is a novel siderophore that features a different chemical structure from those of traditional siderophores. The β-CPA has no obvious influence on the growth of bacterium Pseudomonas aeruginosa PAO1. However, its iron chelator could promote the growth of P. aeruginosa PAO1, suggesting that P. aeruginosa employed siderophores to sequester iron, which is vital for their survival. The study provides the physiochemical evaluation of β-CPA, an unusual skeleton-structure siderophore, which for the first time, was proven to have the ability to bind iron and affect P. aeruginosa growth. This new discovery of siderophore provides an opportunity for developing novel anti-P. aeruginosa drugs.Keywords：marine fungi;β-cyclopiazonic acid;siderophore;Pseudomonas aeruginosa8|0|0Updated：2024-10-12
- Abstract：Two new species belonging to genus Nassarius are described and illustrated based on shell morphology and radular features. Nassarius sanyaensis sp. nov., collected from intertidal zone of Sanya, Hainan Island, China, most resembles Nassarius lyraeformis (Marrat, 1880) in general shell shape, but differs from the latter in having remarkable nodules on shell surface. Nassarius beibuensis sp. nov., sampled from shallow water of Beibu Gulf, is most similar to Nassarius oblongus (Marrat, 1877), but can be distinguished from it mainly in having stronger sculpture. This study expands our knowledge of Nassarius diversity and distribution in China seas.Keywords：Nassariidae;biodiversity;Beibu Gulf;Hainan Island8|0|0Updated：2024-10-12
Biology
- Abstract：Sea cucumber Holothuria leucospilota is one of the most widespread tropical holothurian species. In this study, eukaryotic organism composition in foregut and hindgut contents of H. leucospilota and surrounding sediments was assessed by 18S rRNA gene high-throughput sequencing. Eukaryon richness and diversity in the habitat sediments were significantly higher than those in foregut and hindgut contents of the sea cucumbers (P<0.05). The foregut content group, hindgut content group, and marine sediment group sequences were respectively assigned to 18.20±1.32, 19.40±1.03, and 21.80±0.37 phyla. In the foregut contents, Nematoda (20.18%±9.59%), Mollusca (16.12%±10.49%), Chlorophyta (10.04%± 4.85%), Annelida (8.72%±10.93%), Streptophyta (8.46%±4.65%), and Diatomea (5.99%±2.01%) were the predominant phyla, which showed the eukaryotic food sources of H. leucospilota were primarily belong to the above phyla. The predominant phyla in the hindgut contents were Streptophyta (45.55%± 17.32%), Mollusca (4.93%±4.82%), Arthropoda (5.37%±3.08%), Diatomea (3.88%±2.34%), and Chlorophyta (3.79%±1.59%); and Annelida (37.80%±17.00%), Arthropoda (24.49%±12.53%), Platyhelminthes (7.14%±3.02%), Nematoda (4.14%±0.91%), and Diatomea (5.11%±1.35%) had large contents in the sediments. The comparatively high content of Paris genus in phylum Streptophyta in foregut contents indicated that land plants were one of the primary food sources of H. leucospilota, however the significantly higher contents of Streptophyta in hindgut contents than that in foregut contents might suggest a large part of the terrigenous detritus ingested might not be digested by H. leucospilota. UPGMA and PCoA analysis revealed that eukaryotic organism composition differed significantly between foregut contents of H. leucospilota and ambient sediments, indicating selective feeding feature of H. leucospilota. This study provided useful references for artificial feed of tropical sea cucumbers and enhanced understanding of the ecological roles of detritus-feeding macrobenthos.Keywords：Holothuria leucospilota;food source;18s rRNA gene;gut content;sediment9|0|1Updated：2024-10-12
- Abstract：Although accumulating data demonstrate that dietary supplementation of bamboo vinegar and charcoal powder (BVC) can significantly strengthen the immunity and boost the growth of domestic animals, its application potency still awaits verification in commercial fish species such as the large-scale loach Paramisgurnus dabryanus. The impacts of 90-day dietary supplementation of 1% and 2% BVC on survival and growth performance of the loach, and on the intestinal morphological characteristics and gut microflora were analyzed. Our data show that the large-scale loach supplied with BVC at the experimental doses had significant higher survival rates and better growth performance (indicated by greater weight gain (1.13–1.14 times), higher specific growth rate (1.04 times), and lower feed conversion ratio (0.88–0.89 times)) compared to that of the control (P<0.05). Histological examination revealed significant longer villus (3.22–5.54 times), deeper crypt (1.77–1.87 times), and thicker muscle (1.59–3.17 times) in the intestines of large-scale loach fed with BVC (P<0.05). Furthermore, we found that the gut microflora consisted of significantly fewer proportions of potential pathogenic bacterial species (Aeromonas veronii and Escherichia coli), but significantly greater proportions of beneficial microbes (Lactococus raffinolactis and Faecalibacterium prausnitzii). Therefore, dietary intake of BVC can promote intestinal tract development and optimize gut microflora, by which the survival and growth of large-scale loach may be improved.Keywords：bamboo vinegar;bamboo charcoal;Paramisgurnus dabryanus;growth performance;intestinal morphology;gut microflora8|0|0Updated：2024-10-12
- Abstract：In recirculating aquaculture systems (RASs), the effective treatment of aquaculture tailwater is essential to maintain the health of the RAS. This study investigated the optimal time and method for tailwater treatment during three periods of the aquaculture of the Litopenaeus vannamei: nursery (0–26 d), middle (27–57 d), and later (57–104 d). The variation of several water parameters during the dissolution of total suspended solid (TSS) in tailwater, applied with the effects of ozone on the microorganism and water quality parameters were investigated. Results showed that the TSS concentrations in tailwater decreased with time, although not significantly (P>0.05), whereas total ammonia nitrogen (TAN), nitrite (
- Abstract：Fishing logbook records the fishing behaviors and other information of fishing vessels. However, the accuracy of the recorded information is often difficult to guarantee due to the misreport and concealment. The fishing vessel monitoring system (VMS) can monitor and record the navigation information of fishing vessels in real time, and it may be used to improve the accuracy of identifying the state of fishing vessels. If the VMS data and fishing logbook are combined to establish their relationships, then the navigation characteristics and fishing behavior of fishing vessels can be more accurately identified. Therefore, first, a method for determining the state of VMS data points using fishing log data was proposed. Secondly, the relationship between VMS data and the different states of fishing vessels was further explored. Thirdly, the state of the fishing vessel was predicted using VMS data by building machine learning models. The speed, heading, longitude, latitude, and time as features from the VMS data were extracted by matching the VMS and logbook data of three single otter trawl vessels from September 2012 to January 2013, and four machine learning models were established, i.e., Random Forest (RF), Adaptive Boosting (AdaBoost), K-Nearest Neighbor (KNN), and Gradient Boosting Decision Tree (GBDT) to predict the behavior of fishing vessels. The prediction performances of the models were evaluated by using normalized confusion matrix and receiver operator characteristic curve. Results show that the importance rankings of spatial (longitude and latitude) and time features were higher than those of speed and heading. The prediction performances of the RF and AdaBoost models were higher than those of the KNN and GBDT models. RF model showed the highest prediction performance for fishing state. Meanwhile, AdaBoost model exhibited the highest prediction performance for non-fishing state. This study offered a technical basis for judging the navigation characteristics of fishing vessels, which improved the algorithm for judging the behavior of fishing vessels based on VMS data, enhanced the prediction accuracy, and upgraded the fishery management being more scientific and efficient.Keywords：vessel monitoring system (VMS);fishing logbook;single otter trawler;state identification;machine learning9|0|0Updated：2024-10-12
Aquaculture and Fisheries
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