Journal of Ocean University of China

Biology,Ecology and Threats of Horseshoe Crabs in Asia

  • High Microplastic Contamination in Juvenile Tri-Spine Horseshoe Crabs: A Baseline Study of Nursery Habitats in Northern Beibu Gulf, China

    WANG Xueping;LO Hoi Shing;FU Yijian;WU Zhou;QIN Danmei;HUANG Xing;ZHU Jingmin;CHEUNG Siu Gin;KWAN Kit Yue;

    Microplastics(MPs) are ubiquitous in marine sedimentary environments. Their occurrence in horseshoe crabs and interactions with the sedimentary environment has not been determined. In this study, MPs, mostly microfibers, were found in all extracted gastrointestinal tract(GIT) samples of the juvenile Tachypleus tridentatus from the northern Beibu Gulf, China. The MP concentrations(4 – 53 items ind-1) were higher than those in most marine benthic invertebrates(< 15 items ind-1) reported in Chinese waters, despite their generally low level in habitat sediments(9 – 1818 items kg-1). The correlation between the juveniles and sediments was not evident, but the abundance in juvenile horseshoe crab GITs decreased with ages. The findings were relevant to the life-history characteristics of the species, typically with limited dispersal capability and their spending nine years or longer time living in mangrove wetlands during low tides, with apparent ontogenetic changes in their diets. These baseline data enable a better understanding of MP availability in benthic macroinvertebrates, and the ecological risks present in the ecosystems.

    2022年03期 v.21 521-530页 [查看摘要][在线阅读][下载 1730K]
  • Spatiotemporal Distribution of Asian Horseshoe Crab Eggs Are Highly Intermingled with Anthropogenic Structures in Northern Beibu Gulf, China

    KWAN Kit Yue;FU Yijian;ZHONG Mufeng;KUANG Yang;BAI Haiwei;ZHANG Ce;ZHEN Wenquan;XU Peng;WANG Chun-Chieh;ZHU Junhua;

    Identification, protection and restoration of spawning habitats are vital for protecting the depleted species. Asian horseshoe crabs are ecologically important macroinvertebrates in coastal and estuarine ecosystems. However, their spawning habitat studies were limited to several reports in tropical regions, possibly due to the lack of modified survey methods, particularly in habitats with a lower density of spawning adults, and/or intermingled with anthropogenic structures. In this study, the year-round egg distribution and spawning habitat baselines of Carcinoscorpius rotundicauda and Tachypleus tridentatus were determined in the northern Beibu Gulf, China. Our findings demonstrated that the peak spawning occurred in June – July and ceased in November – January when the average water temperature dropped below 20℃. Egg aggregations were found < 10 cm beneath the sediment surface with regular tidal inundation, regardless of seasonal changes, in the vicinity of natural and artificial structures with elevated, mildly sloping substratum within the high tide zones. The nests were characterized by medium-sized sediment grains(0.5 – 0.9 mm), high temperatures(31 – 34℃), low water contents(0.8% – 0.9%), and total organic carbon contents(0.5% – 0.7%), which might maximize the hatching success. The identified nesting beaches were close to nursery habitats for juveniles, and tidal creeks were present as the possible corridor connecting these two important habitats through the dominant mangrove forests. The findings provide valuable insights in the scope of spawning behavior and nest-site selection of Asian horseshoe crabs under a mixture of natural and artificial structures,which could benefit future management efforts for the exploited spawning populations.

    2022年03期 v.21 531-540页 [查看摘要][在线阅读][下载 3816K]
  • Activity Recording of Free-Ranging Tri-spine Horseshoe Crabs in the Southeastern Coast of Sabah, Borneo

    WATANABE Shinichi;NELSON Bryan Raveen;MANCA Azwarfarid;MOHAMAD Faridah;

    In Inderasabah(southeast Sabah), tri-spine horseshoe crab Tachypleus tridentatus was observed for their locomotion activity using data loggers from September to November in 2015. A female with acceleration and depth-temperature loggers and five males with acceleration loggers were recaptured between 10 and 49 days after their release. From the record of 194 activity days that involve all six T. tridentatus, four horseshoe crabs, including the female, were active throughout the 24.0 h cycle, whereas the activity of the remaining two males was consistent with the 12.4 h cycle. Using the 40-day recording, three horseshoe crabs, including the female, were primarily active around the new moon and full moon, but they were dormant around the first and third quarter moon days. The female spent much time in shallow shores(depth < 0.3 m) during the new moon and full moon. This result indicated that the female attempted to spawn in a minimum of three spring tide periods while lingering in the vicinity. Meanwhile, after spawning, the female spent time foraging in shallow water(depth 0.3 – 18 m). As for the two male individuals, their activity was consistent with semi-lunar periodicity. Therefore, both of them were in amplexus. In addition, a solitary male individual was active only during the first and third quarter moon days. Through activity recording, all the T. tridentatus in Inderasabah was active during daytime and nighttime. This result was contrary to T. tridentatus activity cycles in western Japan, where the species was found to be primarily nocturnal.Perhaps, the regional differences in activity cycles for T. tridentatus were related to their population adaptation toward water temperature,depth, and prey-searching periods.

    2022年03期 v.21 549-556页 [查看摘要][在线阅读][下载 1923K]
  • Effect of Probiotics on Juvenile Tachypleus tridentatus Gut Microbiota

    XIONG Kai;MIAO Fengze;WAIHO Khor;LIU Ximei;FANG James K.H.;HE Jinfeng;HU Menghong;WANG Youji;

    The population of tri-spine horseshoe crabs(HSCs) Tachypleus tridentatus has sharply decreased in recent decades. Domestication and manual releasing are now used to recover it. In order to accelerate the growth of T. tridentatus in indoor environment,in this study, gut microbiota of 2nd instar T. tridentatus was supposed to be improved by putting probiotics in water environment and thus promoted the health and growth of the host. Using 16S r RNA sequencing of gut samples, we examined the intestinal microbiome of juvenile HSCs and studied the effect of probiotics. Results showed that there was no significant difference between groups fed with high and low concentrations(1 × 10~7, 1 × 10~(12) CFU m L-1) of Bacillus subtilis and high concentration(1 × 10~(12) CFU m L~(-1)) of Lactobacillus, and no significant difference compared with the control group, but the diversity of Lactobacillus group with low concentration(1 × 10~7 CFU m L~(-1)) was significantly higher than those of other groups. Microbial-mediated functions predicted by PICRUSt showed that ‘Cellular Processes', ‘Metabolism' and ‘Organismal Systems' pathways significantly increased in groups of Bacillus subtilis and Lactobacillus group with low concentration. The results showed that two types of probiotics with different concentrations have other effects on the structure, richness and function of intestinal microbes. By searching the literature and conducting pre-experiments, we forecasted the short time of breeding under the probiotic environment may not have much effect. The present study for the first time investigated the impact of probiotics on gut microbiota of juvenile HSCs and found them may benefit for the growth and health of HSCs.

    2022年03期 v.21 564-572页 [查看摘要][在线阅读][下载 1699K]
  • Comparison of the Macrozoobenthic Community and Sedimentary Environment with and Without Horseshoe Crab Presence in the Crocodile Island Intertidal Zone, Xiamen, China

    CAI Lizhe;ZHAO Xiaoyu;PENG Wenqing;LIN Jingxiang;YANG Deyuan;RAO Yiyong;FU Sujing;CHEN Xinwei;CAO Wenzhi;

    In order to compare the macrozoobenthic community and sedimentary environment with and without the presence of horseshoe crabs, the benthic macrofauna, sediment grain size, chromium(Cr), cobalt(Co), nickel(Ni), polycyclic aromatic hydrocarbon(PAHs), organic carbon and nitrogen were seasonally investigated at site A(with horseshoe crab presence), sites B and C(without horseshoe crab presence) in the Crocodile Island intertidal zone in Xiamen from June 2018 to July 2019. The results showed that most of the community parameters of benthic macrofauna, population parameters of common benthic macrofauna and environmental parameters were significantly different at the sites with horseshoe crab versus non-horseshoe crab sites. A two-way ANOVA test showed that the densities of Ceratonereis erythraeensis and Sigambra hanaokai had significant site variation. Cluster and nonmetric multi-dimensional scaling(NMDS) analysis showed the community composition of benthic macrofauna was significantly different among the three sampling sites over four seasons. The mean sand content at site A(64.32%) was higher than those at site B(36.01%) and site C(18.86%). Conversely, the mean contents of silt, clay, Cr, Co, Ni, organic carbon, organic nitrogen, phenanthrene,and pyrene at site A were lower than those at site B and site C. These observations are consistent with the expected preferences of horseshoe crabs to live in areas with 60% sand content, which is associated with abundant and edible clamworms in the Crocodile Island intertidal zone, Xiamen.

    2022年03期 v.21 573-582页 [查看摘要][在线阅读][下载 2345K]
  • Indiscriminate Dietary Compositions of Two Asian Horseshoe Crabs,Tachypleus tridentatus and Carcinoscorpius rotundicauda:Evidence from Hemolymph Stable Isotopes

    LI Yuhong;FENG Jianxiang;KWAN Kit Yue;TAN Yiran;WENG Bosen;JIA Ruiling;

    Knowledge of dietary compositions is essential to the recovery of the dwindling populations of horseshoe crabs in China.The feeding habits of Tachypleus tridentatus and Carcinoscorpis rotundicauda of Pearl Bay in southwestern China were studied by stable isotope analysis. Hemolymph samples of the two species were obtained from two age groups living in different habitats(inner,central, and outer Bay). In addition, their potential food source samples were collected in May 2019. Results showed that the mean values of δ~(13)C and δ~(15)N in C. rotundicauda individuals ranged from-19.01‰ to-16.47‰ and from 10.49‰ to 13.5‰, respectively,and those of T. tridentatus ranged from-19.12‰ to-14.96‰ and from 8.78‰ to 13.48‰, respectively. These values indicated that the horseshoe crabs have a wide variety of food sources and therefore are highly omnivorous. No remarkably correlations were found between δ~(13)C and δ~(15)N values and individual widths in the two species. Thirteen potential food sources were selected, in which Sipunculus nudus, Batillaria zonalisi, and Ulva lactuca contributed largely to the dietary compositions of the two species of horseshoe crabs. No significant correlation was found between the feeding habits and habitat geochemical characteristics of the horseshoe crabs. All these results possibly indicate the high diversity of their food sources and the indiscriminate dietary compositions of the two Asian horseshoe crabs.

    2022年03期 v.21 583-590页 [查看摘要][在线阅读][下载 828K]
  • Transcriptome Analysis of the Digestive Tract of Tachypleus tridentatus and Carcinoscorpius rotundicauda

    LI Yuhong;KWAN Kit Yue;LI Sansu;LIU Yingchun;WENG Bosen;HUANG Wenshu;WENG Zhaohong;

    Transcriptome assemblies for the stomach, midgut, and fecal mucosa of Tachypleus tridentatus and Carcinoscorpius rotundicauda are reported for the first time in this study. Genome assembly resulted in 373069 unigenes with an N50 of 1314, while transcriptome assembly resulted in 736378 unigenes and an N50 of 2121. The annotated unigenes showed the highest similarity to fishes, amphibians, and reptiles, with most unigenes closely related to metabolism, translation, biogenesis, signal transduction, energy production, immune response, and secretion. Unigenes(4768) were mapped to KEGG pathways, and the most enriched pathways were involved in translation, environmental information signal processing, metabolism, endocrine system, immune system, nervous system, and varying metabolism. Totally 65889, 2001, and 7162 differentially expressed genes(DEGs) were identified in the stomach, midgut, and fecal mucosa between the two horseshoe crab species, respectively. Compared with C. rotundicauda, 99.95%of the DEGs in the T. tridentatus stomach were down-regulated, while 99.97% of the DEGs of T. tridentatus fecal mucosa and 55.42%of the DEGs of the T. tridentatus midgut were up-regulated. Most midgut DEGs were involved in hydrolase activity, protein metabolism, and cell cytoplasm, while most stomach and fecal mucosa DEGs were involved in catalytic activity and primary metabolic processes. Most stomach DEGs were assigned to the cellular component in cellular macromolecular complexes, while most fecal mucosa DEGs were assigned to the cellular component in cell and cell parts. These results will benefit the investigation of the molecular mechanisms of the digestive tract related to the feeding habits and environmental traces of horseshoe crabs.

    2022年03期 v.21 591-600页 [查看摘要][在线阅读][下载 1353K]
  • Effect of Intertidal Elevation at Tsuyazaki Cove, Fukuoka,Japan on Survival Rate of Horseshoe Crab Tachypleus tridentatus Eggs

    ITAYA Shinji;SHUUNO Mari;ONIKURA Norio;TAI Akira;YANO Shinichiro;

    Physical factors affecting the survival of Tachypleus tridentatus eggs were investigated by translocating their eggs between the high intertidal zone and the low intertidal zone of a known spawning site. The mean egg survival rates per day were highest in the mid intertidal zone(45.1% ± 25.4%) and the lowest in the low intertidal zone(13.3% ± 27.6%). Differences in the elevation, air exposure time, and water content of the spawning ground were significant factors determining the egg survival rates. Excessive or insufficient air exposure time resulted in inadequate water content at higher and lower intertidal zones and could reduce egg survival. On the other hand, moderate saturation and dehydration were repeated with each tidal movement in the mid intertidal zone. This dynamic is considered as one of the crucial factors for the survival of eggs and is considered optimal for spawning. Therefore, the protection of the mid intertidal zone is imperative for maximizing the egg survival rate in Tsuyazaki Cove where almost all suitable nesting sites have disappeared due to coastal development. By protecting these optimal sites for spawning and recovering other optimal sites on suitable beaches, a positive contribution can be made to future management and conservation. The study also suggests that translocating eggs from marginal to optimal spawning sites might be a recovery strategy for this globally endangered species.

    2022年03期 v.21 601-610页 [查看摘要][在线阅读][下载 1433K]
  • Asian Horseshoe Crab Bycatch in Intertidal Zones of the Northern Beibu Gulf: Suggestions for Conservation Management

    WANG Chun-Chieh;CHEN Ruifang;YANG Xin;WEN Yulong;KUANG Yang;ZHANG Ce;ZHU Junhua;KWAN Kit Yue;

    Bycatch poses a severe challenge to global fishery management. Although studies have focused on marine megafauna bycatch, research on relevant issues regarding invertebrates is limited, particularly for the threatened horseshoe crabs. In this study,the distribution of fishing gears and the bycatch intensity of Asian horseshoe crabs in the intertidal zones of the northern Beibu Gulf that harbors the most abundant juvenile Asian horseshoe crabs populations in China were evaluated. Seven intertidal nursery habitats for Tachypleus tridentatus and Carcinoscorpius rotundicauda were surveyed from May to July in 2021. A transect that crossed the tidal creeks and tidal flats between the high tide embankment/vegetation and low tide line of a given habitat was surveyed during the ebb tides. The type, number, and GPS of fishing gears were recorded when sighted, and the number and prosomal width of each horseshoe crab species were measured. Bycatch intensities differed among habitats, ranging from 0.3 to 18.4 and 1.2 to 22.7 individuals per kilometer of transect for T. tridentatus and C. rotundicauda, respectively. Among the three identified fishing gear types,ground cages and stick net sets caused a stronger bycatch pressure on these two species. Most T. tridentatus bycatch and C. rotundicauda bycatch were large individuals in late juvenile and adult stages. Therefore, the ground cages and stick net sets along/near the tidal creeks, mangrove fringe, and low tide line should be regulated and removed to ensure the functionality of the intertidal zone as the spawning corridor and nursery habitat of Asian horseshoe crabs.

    2022年03期 v.21 611-621页 [查看摘要][在线阅读][下载 1613K]
  • Impact of Different Diets on Adult Tri-Spine Horseshoe Crab, Tachypleus tridentatus

    YING Ziwei;BAO Yuyuan;LI Yinkang;YE Guoling;ZHANG Shuhuan;XU Peng;ZHU Junhua;XIE Xiaoyong;

    Effective culture and management of adult tri-spine horseshoe crab, Tachypleus tridentatus can ensure that stock enhancement programs and aquaculture systems are maintained. To explore suitable feed for animals during the breeding season, Pacific oyster(Ostrea gigas)(oyster group; OG) and frozen sharpbelly fish(Hemiculter leucisculus)(frozen fish group; FG) were selected to feed 20 T. tridentatus male and female pairs, respectively. At the end of the experiment, intestinal samples were obtained to measure digestive enzymes activities. The intestinal flora were determined by 16S r DNA sequencing. No eggs were observed in the FG and one T. tridentatus adult died. No animals died in the OG, and 9.7 × 10~4 eggs were obtained. These results show that oysters are more suitable for the development and reproduction of adult T. tridentatus than frozen fish. Additionally, the digestive enzyme activity analysis revealed that animals in the OG exhibited higher protein digestibility than those in the FG, but no significant differences in lipid and carbohydrate uptake were observed between the groups. Furthermore, the intestinal flora analysis showed that operational taxonomic units(OTUs) and the Chao1 index were significantly higher in the OG than in the FG, but no significant difference was observed in the Shannon or Simpson indices between the groups. Our data indicate that the oyster diet improved the intestinal microbial diversity of T. tridentatus. We hypothesize that nutrients, such as oyster-based taurine, proteins, and highly unsaturated fatty acids, improve protease activity in the T. tridentatus digestive tract, alter the intestinal floral structure, and improve the reproductive performance of T. tridentatus.

    2022年03期 v.21 541-548页 [查看摘要][在线阅读][下载 1289K]
  • Influence of Tidal Cycles on Embryonic Rotation, Hatching and Emergence of Mangrove Horseshoe Crab, Carcinoscorpius rotundicauda

    KUANG Yang;TAN Kian Ann;FU Yijian;YANG Xin;XU Peng;ZHEN Wenquan;WANG Xueping;HUANG Xing;ZHU Junhua;WANG Chun-Chieh;KWAN Kit Yue;

    Horseshoe crabs are iconic and ecologically significant macroinvertebrates in coastal environments. The processes and mechanisms of larval hatching in Asian horseshoe crabs that occurs beneath the sand are largely unknown. The spawning and developmental ecology of Tachypleus tridentatus and T. gigas are assumed to be similar to their Atlantic counterpart Limulus polyphemus. However, Carcinoscorpius rotundicauda has been cited as an exception owing to their frequent sightings in muddy mangrove areas even during low tides. To reveal the larval hatching mechanisms, in this study, we examined varying hatching responses of C. rotundicauda embryos within the sediment to the environmental conditions under continuous tidal cycles. During the eight-week experiment, the count of hatched larvae ranged 4% – 30% per week, while the cumulative emergence rate from the sediment was 0 – 47%. Embryos were observed to have the highest active rotation activity in the first two weeks after incubation. The inundation of tidal water significantly enhanced the occurrence of hatching, in which hydration, osmotic shock and possibly agitation had triggered or facilitated the eclosion. The larvae were found to remain in the sediment for approximately 2 – 6 weeks before emergence. In general, C. rotundicauda was found to share a similar hatching mechanism with L. polyphemus. Our findings provide insight into the developmental ecology of Asian horseshoe crabs exposed to varying tidal conditions, and are helpful to the management and protection of their spawning habitats.

    2022年03期 v.21 557-563页 [查看摘要][在线阅读][下载 877K]

Marine and Atmospheric Sciences

  • Roles of Equatorial Ocean Currents in Sustaining the Indian Ocean Dipole Peak

    XING Huibin;WANG Weiqiang;WANG Dongxiao;XU Kang;

    In this study, on the basis of the results of the European Centre for Medium-Range Weather Forecasts Ocean Reanalysis System 4, the response of equatorial ocean currents and their roles during the peak phase of the Indian Ocean Dipole(IOD) are comprehensively explored. During the IOD peak season, a series of ocean responses emerge. First, significant meridional divergence in the surface layer and convergence in the subsurface layer are found in the equatorial region. The equatorial easterly winds and offequatorial wind curl anomalies are found to be responsible for the divergence at 55°– 80°E and the convergence at 70°– 90°E. Second,the meridional divergence and convergence are found to favor a weakened Wyrtki jet(WJ) in the surface layer and an enhanced Equatorial Undercurrent(EUC) in the subsurface layer, respectively. Therefore, these ocean responses provide ocean positive feedback that sustains the IOD peak as the weakened WJ and enhanced EUC help maintain the zonal temperature gradient. Additionally,heat budget analyses indicate that the weakened WJ favors sea surface temperature anomaly warming in the western Indian Ocean,whereas the enhanced EUC maintains the sea surface temperature anomaly cooling in the eastern Indian Ocean.

    2022年03期 v.21 622-632页 [查看摘要][在线阅读][下载 3135K]
  • Experimental Investigation on the Interactions Between Dam-Break Flow and a Floating Box

    WANG Dongxu;DONG Sheng;

    An experiment that investigates the interactions between dam-break flow and a floating box is reported in this paper. The interaction processes are described in detail, and the effects of reservoir depth, clearance between the structure and vertical wall, and structure motion on the observed interactions are discussed. Results indicate that interactions are mild if the reservoir depth is relatively small and most of the water flows through under the structure. However, as the reservoir depth increases, the interactions intensify, and overtopping and wave splashing occur. The incident wave is divided into two parts by the structure: 1) a jet generated by wave impact and 2) the water flowing through under the structure. The water flowing through under the structure is the main factor influencing the motion of the structure. The phenomenon of secondary slamming is observed in all of the test cases, and the relative motion of the structure and free surface explains the occurrence of secondary slamming.

    2022年03期 v.21 633-646页 [查看摘要][在线阅读][下载 3584K]
  • Variational Solution of Coral Reef Stability Due to Horizontal Wave Loading

    ZHANG Qiyi;LONG Quan;LI Xiaowu;

    This paper proposes a theoretical method that can be used in calculating the stability of coral reefs or artificial islands. In this work, we employ the variational limiting equilibrium procedure to theoretically determine the slope stability of coral reefs covered with hard reef shells as a result of horizontal wave loads. A reasonable functional is proposed and its extremum is calculated based on the conservation of energy. Then, we deduce the stability factor Ns of coral reefs under combined vertical self-gravity and horizontal wave loads, which is consistent with the published results. We compare some classic examples of homogeneous slopes without hard shells in order to analyze the accuracy of results generated by this variational procedure. The variational results are accurate and reliable according to the results of a series of detailed calculations and comparisons. Simultaneously, some other influence parameters on the reef stability, including the top-layer tensile strength of coral reef, the amplitude of wave loading, and the tensile crack, are calculated and discussed in detail. The analysis results reveal that the existence of a hard reef shell could enhance the stability of reef slope and that there is a nonlinear relationship between the stability factor Ns, the shear strength, and the thickness Ds of the covered coral reef shell. Furthermore, the emergence of top-layer tensile cracks on the coral reefs reduces their stability,and the action of horizontal wave loads greatly decreases the stability of coral reefs. Thus, the hard shell strength and its thickness Ds,surface tensile crack, and wave loading require more careful attention in the field of practical engineering.

    2022年03期 v.21 647-655页 [查看摘要][在线阅读][下载 1503K]
  • Influence of Autonomous Sailboat Dual-Wing Sail Interaction on Lift Coefficients

    SUN Zhaoyang;HU Feng;YU Jiancheng;ZHAO Wentao;ZHANG Aiqun;

    To analyze the influence of the chord length ratio and angle of attack on lift coefficients and explore the interaction mechanism between the two, we established a calculation model of the pressure distribution coefficient on the airfoil surface and lift coefficient of a dual-wing sail on the basis of the vortex panel method. Computational fluid dynamics was used in auxiliary calculation and analysis. Results revealed a reciprocal interference between the front-wing and rear-wing sails. The total lift coefficient of the dual-sail increased with an increase in the front sail chord length. The lift coefficient of the rear sail decreased with an increase in the front sail chord length or angle of attack. The front sail wake affected the pressure distribution on the upper and lower surfaces of the rear sail leading edge.

    2022年03期 v.21 656-668页 [查看摘要][在线阅读][下载 4020K]
  • Nonlinear Dynamic Analysis and Fatigue Study of Steep Wave Risers Under Irregular Loads

    GU Honglu;GUO Haiyan;LI Xiaomin;LI Fuheng;LIU Zhen;

    As a reliable alternative option for traditional steel catenary risers(SCRs), steep wave risers(SWRs) have been widely applied to deepwater oil and gas production. However, the nonlinear dynamic analysis of SWRs is more complicated than that of traditional SCRs due to their special configuration and significant geometric nonlinearity. Moreover, SWRs are highly susceptible to fatigue failure under the combined excitation of irregular waves and top floater motions(TFMs). In this study, considering irregular waves and TFMs, a numerical SWR model with an internal flow is constructed based on the slender rod model and finite element method. The Newmark-β method is adopted to solve the dynamic behavior of SWR. Moreover, the Palmgren-Miner rule, a specified S-N curve, and rainflow counting method are applied to estimate the fatigue damage. An efficient numerical computation procedure,i.e., DRSWR, is programmed with MATLAB in this study. Calculation results are compared with those of OrcaFlex to verify the accuracy of the DRSWR. The nonlinear dynamic response and fatigue damage of an SWR under the combined excitation of irregular waves and TFMs are obtained, and a comprehensive parametric analysis is then conducted. The analysis results show that the buoyancy section undergoes the highest level of stress and fatigue damage under the combined excitation of irregular waves and TFMs.An internal flow with high velocity and high density produces a high level of fatigue damage. The buoyancy factor and length of the buoyancy section should be set moderately to reconcile the reduction of the top tension with increased fatigue life. These results are expected to provide some reference significance for the engineering design of SWR.

    2022年03期 v.21 669-680页 [查看摘要][在线阅读][下载 1494K]
  • Estimating the Baseline Error of Wide-Swath Altimeters Using Nadir Altimeters via Numerical Simulation

    MIAO Xiangying;JIA Yongjun;LIN Mingsen;MIAO Hongli;

    The baseline roll and length errors for wide-swath altimeters are major error sources in sea surface measurements that exhibit strong spatial characteristics in the cross-track direction. These errors can be identified and estimated in accordance with height differences at crossover points generated with nadir altimeters after excluding the interference from other error sources. Most of the wide-swath altimeter baseline estimation methods considered only the roll error in previous studies. A numerical simulation was conducted in this study using nadir altimeters to estimate the roll and length errors simultaneously to provide a selectable scheme for baseline error estimation and correction for future wide-swath altimeters. Results based on the parameters of the surface water and ocean topography mission and Sentinel-3A show that the correlation coefficient of the roll error between the estimated and simulated values is 0.89, while the correlation coefficient of the length error is 0.85. The sea surface height root mean square error(RMSE) can be reduced from 12.18 cm to 6.45 cm based on the two estimated results. The estimation effect can be increased by using multiple nadir altimeters to form an observation constellation. The numerical simulation of the five nadir altimeter constellation shows that the correlation coefficients of the roll and length errors would increase to 0.97, which reduces the sea surface height RMSE to 2.88 cm.In addition, the stability of this method is indicated in simulation experiments, which introduce different degrees of sea state errors.

    2022年03期 v.21 681-693页 [查看摘要][在线阅读][下载 2632K]
  • Teleseismic P-Wave Tomography of the New Guinea-Solomon Arc System

    FENG Bing;ZHANG Hao;GONG Wei;XING Junhui;LI Deyong;XU Chong;AN Long;

    A P-wave tomographic traveltime inversion was applied to obtain a new model of seismic velocity anomalies beneath the New Guinea-Solomon arc system(PN-SL). The P-wave traveltime data, obtained from the revised International Seismological Center catalog, were recorded by 82 seismic stations in the PN-SL. Under the constraints of the epicenter distance, magnitude, and the number of stations recorded, 15009 effective P-wave traveltime data were selected from 2011 teleseismic events. The obtained model showed that the Solomon Sea Plate subducted beneath the New Britain Island along the New Britain Trench at an angle of > 70°and that the slab can be traced down to a depth of approximately 800 km. Conversely, we cannot observe a high-velocity anomaly exhibited by the subducted Solomon Sea Plate in the deep mantle at the Trobriand Trench, and the slab stopped at a depth of < 200 km.The double subduction of the Solomon Sea Plate strongly modified the subduction patterns of the early subducted Pacific and Australian plates in the mantle along the West Melanesian Trench and the Pocklington Trough, respectively. In addition, the subducted Solomon Sea Plate induced the melting of the upper mantle to form a low-velocity anomaly, which provided the deep dynamic source for the expansion of the Bismarck Sea. Based on the joint consideration of the tomography results and a petrological analysis,the low-velocity anomalies beneath the Solomon Sea and Woodlark Basin are closely related to the early subduction of the Pacific and Australian Plates, respectively.

    2022年03期 v.21 694-706页 [查看摘要][在线阅读][下载 3262K]
  • Simulation of Shallow Gas Invasion Process During Deepwater Drilling and Its Control Measures

    LEI Yani;SUN Jin;WANG Guangjian;

    Shallow gas is considered one of the most serious geological hazards in deepwater drilling because it has the characteristics of suddenness and is difficult to deal with. To perform a quantitative evaluation of shallow gas risk during deepwater drilling, a numerical model for calculating gas invasion volume is established based on gas-water two-phase flow theory. The model considers the effect of the dynamic drilling process, and the influencing factors which affect the gas invasion volume are analyzed. Results indicate that the gas invasion rate and accumulated gas invasion volume increase with increasing bottom-hole pressure difference. A linear relationship exists between gas invasion volume and bottom-hole pressure difference. The duration of gas invasion increases as the shallow gas zone thickness increases, and the accumulated gas invasion volume grows as shallow gas zone thickness increases. The increase in formation permeability, water depth, and rate of penetration will enhance the gas invasion rate. However, these three factors can hardly affect the accumulated gas invasion volume. The gas flow rate increases significantly with increasing burial depth of shallow gas. On the basis of influencing factor analysis, a series of methods that consider different risk levels is proposed to control shallow gas, which can provide a reference for the prevention of shallow gas disasters during deepwater drilling.

    2022年03期 v.21 707-718页 [查看摘要][在线阅读][下载 2233K]
  • Shaking Table Tests and Seismic Response of Three-Bucket Jacket Foundations for Offshore Wind Turbines

    DING Hongyan;PAN Chen;ZHANG Puyang;WANG Le;XU Yunlong;

    The seismic response characteristics of three-bucket jacket foundations for offshore wind turbines(OWTs) and the liquefaction of the surrounding soil are particularly important for the development and application of this type of structure for offshore use. Using the shaking table test and three-dimensional finite element analysis, different magnitudes of simulated earthquake waves were used as inputs to the shaking table to model seismic excitations. The resulting changes in the excess pore water pressure and acceleration response of the soil under horizontal earthquake are compared in this paper. Calculations of the anti-liquefaction shear stress and equivalent shearing stress during the earthquake, determination of the areas prone to liquefaction, and identification of the effect of the three-bucket jacket foundation on the soil liquefaction resistance were conducted by developing a soil-structure finite element model. The development law of the soil's amplification effect on seismic acceleration and the seismic response of the foundation soil under various magnitude earthquake waves were also discussed. Results indicate that liquefying the soil inside the bucket of the foundation is more difficult than that outside the bucket during the excitation of seismic waves due to the large upper load and the restraint of the surrounding hoop. This finding confirms the advantages of the three-bucket jacket foundations in improving the liquefaction resistance of the soil inside the bucket. However, the confinement has a barely noticeable impact on the nearby soil outside the skirt. The phenomenon of soil liquefaction at the bottom of the skirt occurred earlier than that in other positions during the seismic excitation, and the excess pore water pressure slowly dissipated. The acceleration amplification coefficient of the sand outside the bucket increases with depth, but that of the sand inside the bucket is substantially inhibited in the height range of the bucket foundation. This result proves the inhibition effects of the three-bucket jacket foundations on the seismic responses of soils. The liquefied soil layer has a significant effect in absorbing a certain amount of seismic wave energy and reducing the amplification effect.The numerical simulation results are consistent with the phenomenon and data measured during the shaking table test. The current study also verifies the feasibility of the excess pore water pressure ratio and the anti-liquefaction shear stress method for judging soil liquefaction.

    2022年03期 v.21 719-736页 [查看摘要][在线阅读][下载 5481K]
  • Parallel Extraction of Marine Targets Applying OIDA Architecture

    LIU Lin;LI Wanwu;ZHANG Jixian;SUN Yi;CUI Yumeng;

    Computing resources are one of the key factors restricting the extraction of marine targets by using deep learning. In order to increase computing speed and shorten the computing time, parallel distributed architecture is adopted to extract marine targets. The advantages of two distributed architectures, Parameter Server and Ring-allreduce architecture, are combined to design a parallel distributed architecture suitable for deep learning – Optimal Interleaved Distributed Architecture(OIDA). Three marine target extraction methods including OTD_StErf, OTD_Loglogistic and OTD_Sgmloglog are used to test OIDA, and a total of 18 experiments in 3categories are carried out. The results show that OIDA architecture can meet the timeliness requirements of marine target extraction.The average speed of target parallel extraction with single-machine 8-core CPU is 5.75 times faster than that of single-machine single-core CPU, and the average speed with 5-machine 40-core CPU is 20.75 times faster.

    2022年03期 v.21 737-747页 [查看摘要][在线阅读][下载 2936K]
  • Application of Principal Component Analysis(PCA) to the Evaluation and Screening of Multiactivity Fungi

    YANG Zonglin;SHI Yaqi;LI Pinglin;PAN Kanghong;LI Guoqiang;LI Xianguo;YAO Shuo;ZHANG Dahai;

    Continued innovation in screening methodologies remains important for the discovery of high-quality multiactive fungi,which have been of great significance to the development of new drugs. Mangrove-derived fungi, which are well recognized as prolific sources of natural products, are worth sustained attention and further study. In this study, 118 fungi, which mainly included Aspergillus spp.(34.62%) and Penicillium spp.(15.38%), were isolated from the mangrove ecosystem of the Maowei Sea, and 83.1%of the cultured fungi showed at least one bioactivity in four antibacterial and three antioxidant assays. To accurately evaluate the fungal bioactivities, the fungi with multiple bioactivities were successfully evaluated and screened by principal component analysis(PCA), and this analysis provided a dataset for comparing and selecting multibioactive fungi. Among the 118 mangrove-derived fungi tested in this study, Aspergillus spp. showed the best comprehensive activity. Fungi such as A. clavatonanicus, A. flavipes and A. citrinoterreus, which exhibited high comprehensive bioactivity as determined by the PCA, have great potential in the exploitation of natural products and the development of new drugs. This study demonstrated the first use of PCA as a time-saving, scientific method with a strong ability to evaluate and screen multiactive fungi, which indicated that this method can affect the discovery and development of new drugs.

    2022年03期 v.21 763-772页 [查看摘要][在线阅读][下载 905K]
  • Study on Wave Added Resistance of Ships in Oblique Waves Based on Panel Method

    WANG Xujie;ZHANG Ri;ZHAO Jing;CAO Pengfei;

    When the ship is sailing at sea, wave added resistance has great influence on the rapidity and economy of the ship.With the increasing pressure of energy and environmental protection, IMO has proposed the EEDI formula of the newly built ships,which restricts the energy consumption standard of civil ships more strictly. Therefore, a panel method based on three dimensional potential flow theory is proposed to study the problem of wave added resistance in this paper. Firstly, the method solves the motion responses of the ship in the time domain, and then calculates the wave added resistance of the ship by near-field pressure integration method. The wave added resistance of S175 container ship in head and oblique waves are calculated and compared with the experimental data, and the accuracy of the proposed method are verified. At last, the influence of Froude number and wave direction angle on wave added resistance is studied. The proposed method provides an approach of satisfactory accuracy and efficiency for the development of high-performance new ship forms, optimization of ship hull lines, comprehensive performance evaluation of ships and practical navigation guidance.

    2022年03期 v.21 773-781页 [查看摘要][在线阅读][下载 1136K]
  • Abundance, Diversity and Functional Potentials of Planktonic Bacteria and Microeukaryotes in the Coral-Reef System of Xisha Islands, China

    ZHANG Xiaoli;WANG Lei;PENG Saijun;WUZHONG Qiyue;ZHANG Lei;DONG Zhijun;SUN Tingting;LIU Ping;ZHANG Qianqian;ZHAO Jianmin;

    Corals influence microorganisms within the surrounding seawater, yet the diversities and functions of seawater bacteria and microeukaryotes in coral-reef systems have not been well addressed. We collected 40 seawater samples in outer coral reef flats and semi-closed inner lagoons from the surface, middle and bottom layers in the pristine coral-reef system of Xisha Islands, South China Sea. We detected the abundance, composition and distribution of bacteria and microeukaryotes using flow cytometry, qPCR and high throughput sequencing techniques, and profiled the potential ecological roles based on the information of 16S and 18S rDNA sequencing. In terms of flow cytometry, Prochlorococcus dominated the autotrophs with cell abundance ranging from 5.8 × 102 to 5.44 × 103 cells mL-1 seawater. Based on q PCR, the 16S r DNA copies were much higher in coral reef flats than in lagoons(P = 0.003). The bacterial communities held significantly lower diversity in bottom waters compared with surface and middle waters(P < 0.05), which were dominated by SAR11, Flavobacteriales, and Synechococcus. Alveolata represented most of the microeukaryotic communities with Dinophyceae and Syndiniales well represented in all samples. Neither bacterial nor microeukaryotic community exhibited distinct layer or niche pattern, however, Haptophyta and Picozoa decreased with depth and SAR 86, MAST-3 and Picozoa were enriched in lagoons(P < 0.05). To adapt the nutrient-poor and organic matter-rich environment, bacterial nitrogen fixation and assimilatory/dissimilatory nitrate reduction were active in the system, and mixotrophy was the most important trophic strategy among microeukaryotes. The study highlighted the ecological adaptability of seawater microbes to the unique coral-reef environments.

    2022年03期 v.21 748-762页 [查看摘要][在线阅读][下载 2809K]

Life Science

  • Evaluation of Chito-Oligosaccharide(COS) in Vitro and in Vivo: Permeability Characterization in Caco-2 Cells Monolayer and Pharmacokinetics Properties in Rats

    ZHANG Pengpeng;ZHANG Miaomiao;DONG Kaiyu;ZHANG Yicong;YANG Shuang;WANG Yuanhong;JIANG Tingfu;YU Mingming;LV Zhihua;

    Chito-oligosaccharide(COS) had shown a variety of biological activities and potential biomedical implications. The present study investigated the pharmacokinetics, bioavailability, and in vitro absorption of COS with degrees of polymerization(DPs)2-7 and explored the influence of DPs on them. From Caco-2 cell permeation studies, COS were low permeability compounds with no directional effects, suggesting a low in vivo absorption mediated by facilitation diffusion and paracellular absorption. After an intragastrical administration to rats, COS2 showed the highest systemic exposure in six oligosaccharides. The bioavailability of COS2-7 was 7.33%, 6.11%, 4.67%, 4.13%, 4.02%, 0.99%, respectively. Differences in bioavailability for each COS correlated to structural variations, with high DPs contributing to a decrease in bioavailability. In conclusion, COS could be absorbed by the intestinal tract both in vitro and in vivo. The very low oral bioavailability of COS could be due to low permeability. DPs can affect absorption and bioavailability of COS2-7. This study provided evidence for the absorption characteristics of COS2-7 to help us better understanding the pharmacological actions.

    2022年03期 v.21 782-788页 [查看摘要][在线阅读][下载 1041K]
  • Dynamics of the Eukaryotic Microbial Community at the Breeding Sites of the Large Yellow Croaker Pseudosciaena crocea in the Southern East China Sea

    ZHOU Shouheng;ZHENG Shizhan;LV Tianying;YANG Wen;LUKWAMBE Betina;NICHOLAUS Regan;LI Chenghua;ZHENG Zhongming;

    Clarifying eukaryotic microbial spatial distribution patterns and their determinants is an important idea in ecological research. However, information on the distribution patterns of eukaryotic microbial community structures(EMCSs) within oceans remains unclear. In this study, surface water samples from the southern East China Sea(SECS) were collected to investigate the spatiotemporal variation in EMCSs by using 18S rRNA high-throughput sequencing technology and the impact of this variation on Pseudosciaena crocea during the breeding season. The results indicated that the distribution patterns of the eukaryotic microbial community structure were different among the Sansha Bay, Mindong and Wentai reserves and the offshore East China Sea. In addition, there were notable potential effects of EMCSs on fishery activities. The variation partitioning analysis showed the environmental and spatial factors caused 53.4% of the variation in the EMCSs, indicating that spatially structured environmental factors were the key determinants of the EMCSs spatial heterogeneity in the SECS and may have contributed to the general distribution of P.crocea. In addition, all the environmental factors were the main factors driving the distribution of eukaryotic microbes except for total phosphorus. Furthermore, it was noted some phytoplankton such as Poterioochromonas and Rhizophydium of fungi in Sansha Bay can effectively prevent Cyanobacteria blooms. Chrysophyceae are natural high-quality baits for juvenile fish distributed in Sansha Bay, Mindong and Wentai reserves. This study provides a part of the insight into potential eukaryotic community distributions in large water bodies and how they are affected by environmental factors.

    2022年03期 v.21 789-800页 [查看摘要][在线阅读][下载 1967K]
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