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A machine learning-based strategy for predicting the mechanical strength of coral reef limestone using X-ray computed tomography
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作者 Kai Wu Qingshan Meng +4 位作者 Ruoxin Li Le Luo Qin Ke ChiWang Chenghao Ma 《Journal of Rock Mechanics and Geotechnical Engineering》 SCIE CSCD 2024年第7期2790-2800,共11页
Different sedimentary zones in coral reefs lead to significant anisotropy in the pore structure of coral reef limestone(CRL),making it difficult to study mechanical behaviors.With X-ray computed tomography(CT),112 CRL... Different sedimentary zones in coral reefs lead to significant anisotropy in the pore structure of coral reef limestone(CRL),making it difficult to study mechanical behaviors.With X-ray computed tomography(CT),112 CRL samples were utilized for training the support vector machine(SVM)-,random forest(RF)-,and back propagation neural network(BPNN)-based models,respectively.Simultaneously,the machine learning model was embedded into genetic algorithm(GA)for parameter optimization to effectively predict uniaxial compressive strength(UCS)of CRL.Results indicate that the BPNN model with five hidden layers presents the best training effect in the data set of CRL.The SVM-based model shows a tendency to overfitting in the training set and poor generalization ability in the testing set.The RF-based model is suitable for training CRL samples with large data.Analysis of Pearson correlation coefficient matrix and the percentage increment method of performance metrics shows that the dry density,pore structure,and porosity of CRL are strongly correlated to UCS.However,the P-wave velocity is almost uncorrelated to the UCS,which is significantly distinct from the law for homogenous geomaterials.In addition,the pore tensor proposed in this paper can effectively reflect the pore structure of coral framework limestone(CFL)and coral boulder limestone(CBL),realizing the quantitative characterization of the heterogeneity and anisotropy of pore.The pore tensor provides a feasible idea to establish the relationship between pore structure and mechanical behavior of CRL. 展开更多
关键词 coral reef limestone(CRL) Machine learning Pore tensor X-ray computed tomography(CT)
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Coral reef ecological pump for gathering and retaining nutrients and exporting carbon:a review and perspectives 被引量:1
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作者 Linbin Zhou Yehui Tan Liangmin Huang 《Acta Oceanologica Sinica》 SCIE CAS CSCD 2023年第6期1-15,共15页
How coral reefs with high productivity and biodiversity can flourish in oligotrophic tropical oceans has inspired substantial research on coral reef ecosystems.Increasing evidence shows that similar to water in an oas... How coral reefs with high productivity and biodiversity can flourish in oligotrophic tropical oceans has inspired substantial research on coral reef ecosystems.Increasing evidence shows that similar to water in an oasis in the desert,there are stable nutrient supplies to coral reefs in oligotrophic oceans.Here,with emphasis on the fluxes of organic matter,we summarize at the ecosystem level(1)the multiple input pathways of external nutrients,(2)the storage of nutrients in reef organisms,(3)the efficient retaining and recycling of dissolved and particulate organic matter within coral reef ecosystems,(4)the distinctly high phytoplankton productivity and biomass inside and near oceanic coral reefs,and(5)the export of reef-related organic carbon to adjacent open oceans.These properties enable coral reefs to function as ecological“pumps”for gathering nutrients across ecosystems and space,retaining and recycling nutrients within the ecosystem,supporting high phytoplankton productivity,and exporting organic carbon to adjacent open oceans.Particularly,the high phytoplankton productivity and biomass make waters around coral reefs potential hotspots of carbon export to ocean depths via the biological pump.We demonstrate that organic carbon influx is vital for coral reef ecosystems’carbon budget and carbon export.The concept of the coral reef ecological pump provides a framework to improve the understanding of the functioning of the coral reef ecosystem and its responses to disturbance.Prospects of the coral reef ecological pump in coral reef studies are discussed in changing oceans driven by human activities and global change in the Anthropocene. 展开更多
关键词 Darwin’s Paradox coral reef NUTRIENTS coral reef ecological pump carbon export ocean carbon cycle
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Stressed Coral Reef Identification Using Deep Learning CNN Techniques
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作者 S.P.Aruna M.Thamarai 《Journal of Electronic & Information Systems》 2023年第2期1-9,共9页
Deep learning is a machine learning technique that allows the computer to process things that occur naturally to humans.Today,deep learning techniques are commonly used in computer vision to classify images and videos... Deep learning is a machine learning technique that allows the computer to process things that occur naturally to humans.Today,deep learning techniques are commonly used in computer vision to classify images and videos.As a result,for challenging computer vision problems,deep learning provides state of the art solutions to it.Coral reefs are an essential resource of the earth.A new study finds the planet has lost half of its coral reefs since 1950.It is necessary to restore and prevent damage to coral reefs as they play an important role in maintaining a balance in the marine ecosystem.This proposed work helps to prevent the corals from bleaching and restore them to a healthy condition by identifying the root cause of the threats.In the proposed work,using deep learning CNN techniques,the images are classified into Healthy and Stressed coral reefs.Stressed coral reefs are an intermediate state of coral reef between healthy and bleached coral reefs.The pre-trained models Resnet50 and Inception V3 are used in this study to classify the images.Also,a proposed CNN model is built and tested for the same.The results of Inception V3 and Resnet50 are improved to 70%and 55%by tuning the hypermeters such as dropouts and batch normalisation.Similarly,the proposed model is tuned as required and obtains a maximum of up to 90%accuracy.With large datasets,the optimum amount of neural networks and tuning it as required brings higher accuracy than other methods. 展开更多
关键词 Stressed coral reef Deep learning Convolutional neural network Pre-trained models
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Coral Reef and High Sea Level at Luhuitou, Hainan Island during the Holocene 被引量:2
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作者 黄德银 施祺 张叶春 《Marine Science Bulletin》 CAS 2007年第2期61-70,共10页
According to the field survey and ^14C dating at Luhuitou, southern Hainan Island, a subsiding area, the authors conclude the high sea level history recorded by coral reef in the Holocene. At least 4 sea level high-st... According to the field survey and ^14C dating at Luhuitou, southern Hainan Island, a subsiding area, the authors conclude the high sea level history recorded by coral reef in the Holocene. At least 4 sea level high-stands can be identified from the distribution of coral reef ages: 7300 - 6000 cal.aBP, 4800 - 4700 cal.aBP, 4300 - 4200 cal.aBP and 3100 - 2900 cal.aBP. The highest sea level occurred around 7300 - 6700 cal.aBP, and biological-morphological zones took their shape during the stage. The later coral reefs developed in ponds, depressions, and developed outwards on both sides of Luhuitou peninsula. The modern coral reefs are developing in out reef flat and reef-front slope. Moreover, the time of high sea levels in the northern South China Sea recorded by coral reefs in the Luhuitou peninsula can link up with that in other parts of South China Sea. That means the high sea levels in the South China Sea during the Holocene, which are relative to the warming climate, have the global background. 展开更多
关键词 coral reef high sea level Luihuitou HOLOCENE
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Simulation of global ocean acidification and chemical habitats of shallow-and cold-water coral reefs 被引量:1
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作者 ZHENG Mei-Di CAO Long 《Advances in Climate Change Research》 SCIE 2014年第4期189-196,共8页
Using the UVic Earth System Model, this study simulated the change of seawater chemistry and analyzed the chemical habitat surrounding shallow- and cold-water coral reefs from the year 1800 to 2300 employing RCP2.6, R... Using the UVic Earth System Model, this study simulated the change of seawater chemistry and analyzed the chemical habitat surrounding shallow- and cold-water coral reefs from the year 1800 to 2300 employing RCP2.6, RCP4.5, RCP6.0, and RCP8.5 scenarios. The model results showed that the global ocean will continue to absorb atmospheric CO2. Global mean surface ocean temperature will rise 1.1-2.8 K at the end of the 21st century across RCP scenarios. Meanwhile, the global mean surface ocean pH will drop 0.14--0.42 and the ocean surface mean con- centration of carbonate will decrease 20%--51% across the RCP scenarios. The saturated state of sea water with respect to calcite carbonate minerals (t2) will decrease rapidly. During the pre-industrial period, 99% of the shallow-water coral reefs were surrounded by seawater with t2 〉 3.5 and 87% of the deep-sea coral reefs were surrounded by seawater with aragonite supersaturation. Within the 21st century, except for the high mitigation scenario of RCP2.6, almost none shallow-water coral reefs will be surrounded by seawater with g2 〉 3.5. Under the intensive emission scenario of RCP8.5, by the year 2100, the aragonite saturation horizon will rise to 308 m under the sea surface from 1138 m at the pre- industrial period, thus 73% of the cold-water coral reefs will be surrounded by seawater with aragonite undersaturation. By the year 2300, only 5% of the cold-water coral reefs will be surrounded by seawater with aragonite supersaturation. 展开更多
关键词 Simulation research Aragonite saturation state Ocean acidification Shallow-water coral reefs Cold-water coral reefs
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Methanation of syngas over coral reef-like Ni/Al_2O_3 catalysts 被引量:23
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作者 Shengli Ma Yisheng Tan Yizhuo Han 《Journal of Natural Gas Chemistry》 EI CAS CSCD 2011年第4期435-440,共6页
Coral reef-like Ni/Al2O3 catalysts were prepared by co-precipitation of nickel acetate and aluminium nitrate with sodium carbonate aqueous solution in the medium of ethylene glycolye.Methanation of syngas was carried ... Coral reef-like Ni/Al2O3 catalysts were prepared by co-precipitation of nickel acetate and aluminium nitrate with sodium carbonate aqueous solution in the medium of ethylene glycolye.Methanation of syngas was carried out over coral reef-like Ni/Al2O3 catalysts in a continuous flow type fixed-bed reactor.The structure and properties of the fresh and used catalysts were studied by SEM,N2 adsorption-desorption,XRD,H2-TPR,O2-TPO,TG and ICP-AES techniques.The results showed that the coral reef-like Ni/Al2O3 catalysts exhibited better activity than the conventional Ni/Al2O3-H2O catalysts.The activities of coral reef-like catalysts were in the order of Ni/Al2O3-673Ni/Al2O3-573Ni/Al2O3- 473Ni/Al2O3-773.Ni/Al2O3-673-EG catalyst showed not only good activity and improved stability but also superior resistance to carbon deposition,sintering,and Ni loss.Under the reaction conditions of CO/H2(molar ratio)=1:3,593 K,atmospheric pressure and a GHSV of 2500 h-1,CH4 selectivity was 84.7%,and the CO conversion reached 98.2%. 展开更多
关键词 METHANATION SYNGAS coral reef-like Ni/Al2O3 catalysts CALCINATION
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Mechanical Properties and Microstructure of Portland Cement Concrete Prepared with Coral Reef Sand 被引量:22
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作者 王乾坤 LI Peng +2 位作者 田亚坡 CHEN Wei SU Chunyi 《Journal of Wuhan University of Technology(Materials Science)》 SCIE EI CAS 2016年第5期996-1001,共6页
The feasibility of using coral reef sand(CRS) in Portland cement concrete is investigated by testing the mechanical property and microstructure of concrete. The composition, structure and properties of the CRS are a... The feasibility of using coral reef sand(CRS) in Portland cement concrete is investigated by testing the mechanical property and microstructure of concrete. The composition, structure and properties of the CRS are analyzed. Mechanical properties and microstructure of concrete with CRS are studied and compared to concrete with natural river sand. The relationship between the microstructure and performance of CRS concrete is established. The CRS has a porous surface with high water intake capacity, which contributes to the mechanical properties of concrete. The interfacial transition zone between the cement paste and CRS is densified compared to normal concrete with river sand. Hydration products form in the pore space of CRS and interlock with the matrix of cement paste, which increases the strength. The total porosity of concrete prepared with CRS is higher than that with natural sand. The main difference in pore size distribution is the fraction of fine pores in the range of 100 nm. 展开更多
关键词 coral reef sand concrete mechanical properties microstructure interfacial transition zone
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Connectivity of fish assemblages along the mangrove-seagrasscoral reef continuum in Wenchang, China 被引量:2
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作者 Jianguo Du Meiling Xie +4 位作者 Yuyu Wang Zehao Chen Wenhua Liu Jianji Liao Bin Chen 《Acta Oceanologica Sinica》 SCIE CAS CSCD 2020年第8期43-52,共10页
Understanding the connectivity of fish among different typical habitats is important for conducting ecosystembased management, particularly when designing marine protected areas(MPA) or setting MPA networks. To clarif... Understanding the connectivity of fish among different typical habitats is important for conducting ecosystembased management, particularly when designing marine protected areas(MPA) or setting MPA networks. To clarify of connectivity among mangrove, seagrass beds, and coral reef habitats in Wenchang, Hainan Province,China, the fish community structure was studied in wet and dry seasons of 2018. Gill nets were placed across the three habitat types, and the number of species, individuals, and body size of individual fish were recorded. In total, 3 815 individuals belonging to 154 species of 57 families were collected. The highest number of individuals and species was documented in mangroves(117 species, 2 623 individuals), followed by coral reefs(61 species,438 individuals) and seagrass beds(46 species, 754 individuals). The similarity tests revealed highly significant differences among the three habitats. Approximately 23.4% species used two habitats and 11.0% species used three habitats. A significant difference(p<0.05) in habitat use among eight species(Mugil cephalus, Gerres oblongus, Siganus fuscescens, Terapon jarbua, Sillago maculata, Upeneus tragula, Lutjanus russellii, and Monacanthus chinensis) was detected, with a clear ontogenetic shift in habitat use from mangrove or seagrass beds to coral reefs. The similarity indices suggested that fish assemblages can be divided into three large groups namely coral, seagrass, and mangrove habitat types. This study demonstrated that connectivity exists between mangrove–seagrass–coral reef continuum in Wenchang area;therefore, we recommend that fish connectivity should be considered when designing MPAs or MPA network where possible. 展开更多
关键词 CONNECTIVITY FISH MANGROVE SEAGRASS coral reef Wenchang northern South China Sea
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Analysis on coral reefs mapping using SPOT5 data at the Dongsha Atoll 被引量:1
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作者 CHEN Jianyu MAO Zhihua ZHANG Huaguo WU Junping CHEN Xiaodong PAN Delu 《Acta Oceanologica Sinica》 SCIE CAS CSCD 2007年第2期26-35,共10页
Coral reefs are an sensitive-to-environment complex marine ecosystem. The ecosystem of corals is rich in biodiversity. Remote sensing offers a powerful tool for categorizing coral reefs and is the most cost - effectiv... Coral reefs are an sensitive-to-environment complex marine ecosystem. The ecosystem of corals is rich in biodiversity. Remote sensing offers a powerful tool for categorizing coral reefs and is the most cost - effective approach for the large - scale reef survey. The Dongsha Atoll, more than 300 km2 with an average depth of 10 m, is located at the northern continental margin of the South China Sea. It has been abused by destructive fishing during recent decades. Three satellite imageries (Quickbird2, ETM + and SPOTS) are used to evaluate the capabilities of SPOT5 imagery to provide data that are useful for categorizing the current distribution of coral reefs therein. During the data processing, unsupervised classification functions are adopted for ETM + and SPOT5 data, while the supervised classification method is used for Quickbird2. The classes are (or not) merged into coral reef, and then will be operated by vectorization, simplification, and topological analysis. There are 1 331 coral reefs larger than 100 m2 with a detection limit of 3 × 3 pixels at the multi - band data of Quickbird2, which is taken as the comparison baseline. The results extracted from SPOT5 and ETM images are less in number and area than those from the Quickbird2 image, whereas the results from SPOT5 data are better than those of ETM data at the silty lagoon due to its higher resolution. SPOT5 XS band 2 fails to distinguish the deep substrate inside the atoll compared with ETM data because of its poor penetration capability. Only SPOT XS band 1 cannot be used to differentiate coral reef from sand bottom. Merging the SPOT5 multi - bands data with the spatial resolution of SPOT5 pan - data and referring to ETM imagery are expected to provide an optimal satellite - based approach for mapping of coral reefs. 展开更多
关键词 coral reef Dongsha Atoll SPOT5 Quickbird2
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Spatial and Temporal Variability of Thermal Stress to China's Coral Reefs in South China Sea 被引量:7
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作者 ZUO Xiuling SU Fenzhen +2 位作者 WU Wenzhou CHEN Zhike SHI Wei 《Chinese Geographical Science》 SCIE CSCD 2015年第2期159-173,共15页
Coral bleaching, caused by elevated sea surface temperature(SST), is occurring more frequently and seriously worldwide. Due to the lack of field observations, we understand little about the large-scale variability of ... Coral bleaching, caused by elevated sea surface temperature(SST), is occurring more frequently and seriously worldwide. Due to the lack of field observations, we understand little about the large-scale variability of thermal stress in the South China Sea(SCS) and its effect on China's coral reefs. This paper used 4-km high resolution gap-filled SST(Filled SST) data and thermal stress data related to coral bleaching derived from Coral Reef Temperature Anomaly Database(Co RTAD) to quantify the spatial and temporal characteristics of chronic thermal stress and acute thermal stress to China's coral reefs in SCS from 1982 to 2009. We analyzed the trend of SST in summer and the thermal stress frequency, intensity and duration during this period. The results indicate that, as a chronic thermal stress, summer mean SST in SCS shows an average upward trend of 0.2℃/decade and the spatial pattern is heterogeneous. Waters of Xisha Islands and Dongsha Islands of the northern SCS are warming faster through time compared to Zhongsha Islands and Nansha Islands sea areas of the southern SCS. High frequency bleaching related thermal stress events for these reefs are seen in the area to the northwest of Luzon Island. Severe anomaly thermal stress events are more likely to occur during the subsequent year of the El Nino year for these coral reefs. Besides, the duration of thermal stress varies considerably by anomaly year and by region. 展开更多
关键词 coral reef sea surface temperature(SST) thermal stress El Nino-Southern Oscillation(ENSO) South China Sea(SCS)
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Variational Solution of Coral Reef Stability Due to Horizontal Wave Loading 被引量:1
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作者 ZHANG Qiyi LONG Quan LI Xiaowu 《Journal of Ocean University of China》 SCIE CAS CSCD 2022年第3期647-655,共9页
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 determ... 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. 展开更多
关键词 coral reef stability tensile crack variational solution horizontal wave loading
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Dynamic simulation of tropical coral reef ecosystem being disturbed by multiple situations 被引量:1
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作者 Geng Wang Rui Dong +1 位作者 Huimin Xu Dewen Ding 《Acta Oceanologica Sinica》 SCIE CAS CSCD 2021年第9期105-116,共12页
In consideration of the rapid degradation of coral reef ecosystems, the establishment of models is helpful to comprehend the degradation mechanism of coral reef ecosystems and predict the development process of coral ... In consideration of the rapid degradation of coral reef ecosystems, the establishment of models is helpful to comprehend the degradation mechanism of coral reef ecosystems and predict the development process of coral reef communities. According to the characteristics of complex ecosystem of tropical coral reefs in China, the coral reef functional group is the core level variable;combined with the multiple feedback effects of coral reef functional groups and environmental changes, the study presents a coral reef ecosystem dynamics model with hermatypic corals as the core. Based on the simulation of the assumed initial value and the internal feedback of the system, the results show that in the basic simulation(relative health conditions), the coverage area of live corals and coral reefs generally decreased first and then increased, and increased by 4.67% and 6.38% between2010 and 2050, respectively. Based on the calibration model and the current situation of the studied area, the multi-factor disturbance effects of coral reef communities were simulated and explored by setting up three scenarios involving fishing policy, terrestrial deposition, and inorganic nitrogen emissions. Among them, in the single factor disturbance, the fishing policy exerts the most direct impact on the community decline;and the succession phenomenon is obvious;the terrestrial sedimentation has a faster and more integrated effect on the community decline;the effect of inorganic nitrogen emission on the community decline is relatively slow. In the double/multi-factor disturbance, the superimposed disturbance will aggravate the multi-source feedback effect of the coral reef communities development, accelerate the community decay rate, and make its development trajectory more complicated and diverse. This method provides a scientific and feasible method for simulating the damage of long-term coral reef community and exploring the development law and adaptive management of coral reef ecosystems. In the future, it can be further studied in the ecological restoration process and decisionmaking direction of coral reefs. 展开更多
关键词 coral reef ecosystem system dynamics situational disturbance SIMULATION
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Spatio-temporal Variations of Sea Surface Wind in Coral Reef Regions over the South China Sea from 1988 to 2017 被引量:1
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作者 HE Xin CHEN Zhenghua +2 位作者 LU Yongqiang ZHANG Wei YU Kefu 《Chinese Geographical Science》 SCIE CSCD 2021年第3期522-538,共17页
The seasonal and interannual variabilities of sea surface wind(SSW)in the South China Sea(SCS),especially in coral reef regions such as Nansha Islands,Xisha Islands,Zhongsha Islands and Dongsha Islands were investigat... The seasonal and interannual variabilities of sea surface wind(SSW)in the South China Sea(SCS),especially in coral reef regions such as Nansha Islands,Xisha Islands,Zhongsha Islands and Dongsha Islands were investigated in detail using the Blended Sea Winds dataset(1988-2017).Annual and monthly variations of SSW and sea surface temperature(SST)in the four zones were investigated.Empirical Orthogonal Function(EOF)analysis of wind field was performed to aid in better understanding the different spatial patterns.The results indicate that,as observed in the spatial distribution of the first mode of monthly mean wind speed anomaly,the mag-nitudes in the four island zones are all negative and are similar to each other,showing that the variations of SSW in the four island zones are consistent.In the second mode,the magnitudes in Nansha Islands are opposite to those in the other three zones.The spatial distribution of the third mode reflects regional differences.The maximum annual SSW appears in Dongsha Islands,and the minimum appears in Nansha Islands.The interannual variations of SSW in all island zones are basically concurrent.The island zones with high SSW mostly have low SST,and vice versa.There may be an inverse relationship between SSW and SST in coral reef regions in the SCS.The multiyear monthly variations of SSW in the island zones present a'W'-shaped structural variation.Each island undergoes two months of minimum SSW every year,one during March-May(MAM)and the other during September-November(SON).Both months are in mon-soon transition periods.During the months with low SSW,high SST appears.The SST peaks almost correspond to the SSW troughs.This further indicates that SSW and SST may have opposite changes in coral reef regions.Coral bleaching events often correspond to years of high SST and low SSW. 展开更多
关键词 sea surface wind(SSW) Empirical Orthogonal Function(EOF) MONSOON coral reefs South China Sea(SCS)
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ESR and U-series ages of coral reef samples from shallow drill holes in the South China Sea 被引量:1
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作者 Ye Yuguang, Gao Juncheng, He jie, Diao Shaobo, Liu Xinbo and Du Yajing Institute of Marine Geology, Ministry of Geology and Mineral Resources, Qingdao, 266071, ChinaNational Institute of Metrology, Beijing, 100013, China 《Acta Oceanologica Sinica》 SCIE CAS CSCD 1991年第3期423-431,共9页
The ages of coral reef samples from several shallow drill holes in the South China Sea are determined by ESR and U-series (230Th/234U) methods. The experimental results show ideal agreement between ESR and U-series ag... The ages of coral reef samples from several shallow drill holes in the South China Sea are determined by ESR and U-series (230Th/234U) methods. The experimental results show ideal agreement between ESR and U-series ages and that the coral reefs were formed in the early Holocene. In the determination of natural total dose of coral reef by use of the additive dose method good results can be obtained by exponential fitting, no matter how the effect of dose saturation is. It was found that the ratio of the natural ESR signal intensity ( I0) to the ESR signal intensity at dose saturation ( Imax) of sample can reflect the significance of a irradiation efficiency-k value. Using the k value of sample determined by the formula given in this paper, the precision of ESR dating of marine carbonates can be improved. 展开更多
关键词 Th ESR and U-series ages of coral reef samples from shallow drill holes in the South China Sea
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Reconstructing Environmental Changes of a Coastal Lagoon with Coral Reefs in Southeastern Hainan Island 被引量:2
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作者 ZHOU Liang GAO Shu +4 位作者 GAO Jianhua ZHAO Yangyang HAN Zhuochen YANG Yang JIA Peihong 《Chinese Geographical Science》 SCIE CSCD 2017年第3期402-414,共13页
Coastal lagoons with small catchment basins are highly sensitive to natural processes and anthropogenic activities. To figure out the environmental changes of a coastal lagoon and its contribution to carbon burial, tw... Coastal lagoons with small catchment basins are highly sensitive to natural processes and anthropogenic activities. To figure out the environmental changes of a coastal lagoon and its contribution to carbon burial, two sediment cores were collected in Xincun Lagoon, southeastern Hainan Island and (210) ~Pb activities, grain size parameters, total organic carbon(TOC), total nitrogen(TN), total inorganic carbon(TIC) and stable carbon isotopes(δ^(13)C) were measured. The results show that in 1770–1815, the decreasing water exchange capacity with outer open water, probably caused by the shifting and narrowing of the tidal inlet, not only diminished the currents and fined the sediments in the lagoon, but also reduced the organic matter of marine sources. From 1815 to 1950, the sedimentary environment of Xincun Lagoon was frequently influenced by storm events. These extreme events resulted in the high fluctuation of sediment grain size and sorting, as well as the great variation in contributions of terrestrial(higher plants, soils) and marine sources(phytoplankton, algae, seagrass). The extremely high content of TIC, compared to TOC before 1950 could be attributed to the large-scale coverage of coral reefs. However, with the boost of seawater aquaculture activities after 1970, the health growth of coral species was severely threatened, and corresponding production and inorganic carbon burial flux reduced. The apparent enhanced inorganic carbon burial rate after 1990 might result from the concomitant carbonate debris produced by seawater aquaculture. This result is important for local government long-term coastal management and environmental planning. 展开更多
关键词 environmental change carbon burial flux organic matter coral reef human activity coastal lagoon southeastern Hainan Island
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Heavy metal content in coral reef sediments from Red Sea of Yemen and its significance on marine environment 被引量:1
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作者 Nabil A.AL-SHAWAFI Abdulhakeem AL-KHOLIDI Aref M.O.AL-JABALI 《Global Geology》 2009年第2期100-104,共5页
In order to determine and assess the concentrations of trace elements in coral reefs sediments from Red Sea of Yemen, sediment samples were collected, treated and analyzed for cadmium, chromium, cobalt, copper, mangan... In order to determine and assess the concentrations of trace elements in coral reefs sediments from Red Sea of Yemen, sediment samples were collected, treated and analyzed for cadmium, chromium, cobalt, copper, manganese, nickel, lead, iron, zinc and vanadium by the atomic absorption spectrometric analysis. The result is that cadmium, cobalt and lead concentrations were high and other elements are low or the same as natural background. It is concluded that the high cadmium, cobalt and lead levels in coral reefs sediments will have negative effects on marine life of the sites, so further researches are needed to characterize the sources fate, biogeochemical processes and impacts of these trace elements on coral reefs and marine of the region. 展开更多
关键词 heavy metal coral reef sediments marine environment
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Change in coral reef benthic communities in the Lembeh Strait and Likupang, North Sulawesi, Indonesia
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作者 HADI Tri Aryono SIHOUKA Jimmy +2 位作者 SHI Xiaofeng BUDIYANTO Agus SUHARSONO 《Acta Oceanologica Sinica》 SCIE CAS CSCD 2018年第12期45-54,共10页
Anthropogenic impacts and natural disturbances have been intense recently in the global scale, affecting the composition of coral reef benthic communities from coral to algal dominated reefs. However, this condition d... Anthropogenic impacts and natural disturbances have been intense recently in the global scale, affecting the composition of coral reef benthic communities from coral to algal dominated reefs. However, this condition does not always occur considering corals are able to recover when the stressors falter. This study aims to investigate the change in coral reef benthic communities and the relationship among benthic categories. The study was carried out in 2014 and 2016 at five sites, three sites in the Lembeh Strait and two sites in Likupang, North Sulawesi Province. Underwater Photo Transect(UPT) was used at depth of around 4–6 m in slope areas. The result indicated that the benthic communities were slightly changing: the percent covers of hard corals, sponges, soft corals, macroalgae and substrate categories were not significantly different between the years but category of others, particularly seasonally growing hydroid, increased significantly, occupying the available substrates and overtopping other benthos surrounding. The study also found that there was a significant relationship between the change in benthic gradient and the number of hard coral colonies: when the composition becomes less complex, the number of colony declines. In contrast, the hard coral diversity remained unchanged, suggesting the coral reefs apparently have an ecological resilience(sustainable species diversity) against the change although ecological complexity declines. In addition, the hard coral cover was significantly correlated with soft coral and sponge covers, which did not change significantly among the years. In general, the coral reefs in North Sulawesi might experience a temporary blip due to the increasing percent cover of others, and be predicted to recover as there was no indication of soft corals and sponges to increase significantly. However, it is necessary to investigate the dynamic of benthic communities in different depth gradients to gain a comprehensive understanding as the communities respond differently to the light intensity. 展开更多
关键词 coral reef benthic community percent cover Lembeh Strait Likupang
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Remote sensing expert system of South China Sea coral reefs
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作者 Wang Yanfeng and Liu Baoyin 《Acta Oceanologica Sinica》 SCIE CAS CSCD 1996年第4期437-445,共9页
Based on the remote sensing information and related condition such as geology, geomorphology, hydrology and meteorology, a remote sensing expert system of the South China Sea coral reefs is developed by using a new r... Based on the remote sensing information and related condition such as geology, geomorphology, hydrology and meteorology, a remote sensing expert system of the South China Sea coral reefs is developed by using a new remote sensing twin-tree structure. The object is recognized and the type of coral reef is distinguished through the combined utilization of spectrum and image primitive's spatial relation and related information. 展开更多
关键词 South China Sea coral reef remote sensing expert system
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Diverse habitat preferences of two sea cucumber species and the seasonal change in a coral reef area
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作者 Chunyang SUN Duanjie HUANG +3 位作者 Qiang XU Fei GAO Xiubao LI Aimin WANG 《Journal of Oceanology and Limnology》 SCIE CAS CSCD 2022年第4期1578-1591,共14页
Diff erent sea cucumbers have diff erent preferred habitats and seasonal changes,which is still lack of detailed research.This study selects two common tropical sea cucumbers(Holothuria edulis and Stichopus chloronotu... Diff erent sea cucumbers have diff erent preferred habitats and seasonal changes,which is still lack of detailed research.This study selects two common tropical sea cucumbers(Holothuria edulis and Stichopus chloronotus)to explore the reasons that aff ect their habitat selection and seasonal changes,so as to provide support for the spatial planning of sea cucumbers reserve in coral reef area.The study area is a compound distribution area of living coral reefs and sandy bottom in the north of Wuzhizhou Island.The survey time is January,April-September,2019.Three fi xed transects(G,H,and Q)were selected to reveal the population ecological characteristics of them in the typical dry season(January,April,May,and June)and rainy season(July,August,and September).The variation range of density for H.edulis and S.chloronotus were 2.0-8.9 inds./10 m^(2) and 0.2-0.7 inds./10 m^(2),respectively.The population density in rainy season was signifi cantly higher than that in dry season(P<0.05).H.edulis tends to be distributed in deeper water.The distribution of H.edulis was signifi cant positively correlated with the sand coverage and sand continuity in G transect(P<0.05),and signifi cant negatively correlated with live coral coverage in three transects(P<0.01).The shift from dry season to rainy season is a key factor aff ecting their habitat preference.In dry season,the preferred habitats of S.chloronotus are small rock(SR),sand(S),and small coral reef(SCR),while the H.edulis is S,SR,and dead coral rubbles(DCR).In rainy season,the preferred habitats of S.chloronotus are shift to SCR and SR,while the H.edulis is SCR,DCR,and sand. 展开更多
关键词 habitat preference coral reef population density Holothuria edulis Stichopus chloronotus
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Construction and analysis of a coral reef trophic network for Qilianyu Islands,Xisha Islands
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作者 Xiaofan Hong Zuozhi Chen +4 位作者 Jun Zhang Yan’e Jiang Yuyan Gong Yancong Cai Yutao Yang 《Acta Oceanologica Sinica》 SCIE CAS CSCD 2022年第12期58-72,共15页
Qilianyu Islands coral reefs(QICR),located in the northeastern part of the South China Sea,has been affected by human activities and natural disturbance.To characterize the trophic structure,ecosystem properties and k... Qilianyu Islands coral reefs(QICR),located in the northeastern part of the South China Sea,has been affected by human activities and natural disturbance.To characterize the trophic structure,ecosystem properties and keystone species of this region,a food-web model for the QICR is developed using methods involving a mass-balance approach with Ecopath with Ecosim software.Trophic levels range from 1.00 for detritus and primary producers to 3.80 for chondrichthyes.The mean trophic transfer efficiency for the entire ecosystem is 13.15%,with 55%of total energy flow originating from primary producers.A mixed trophic impact analysis indicates that coral strongly impacts most components of this ecosystem.A comparison of our QICR model with that for other coral reef ecosystems suggests that the QICR ecosystem is immature and/or is degraded. 展开更多
关键词 South China Sea Qilianyu Islands coral reef Ecopath model food webs ecosystem characteristic
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