The persistence and habitability of coral reef islands in future extreme oceanographic conditions has received increasing attention in the recent decade,concerning that the sea level rise(SLR)and more frequent and int...The persistence and habitability of coral reef islands in future extreme oceanographic conditions has received increasing attention in the recent decade,concerning that the sea level rise(SLR)and more frequent and intense storms in the context of global climate change are expected to destabilize those islands.Here,we conduct a set of wave-flume laboratory experiments focusing on the morphodynamic change of reef islands to varying ocean forcing conditions(wave height and SLR).Subsequently,a phase-resolving XBeach numerical model is adopted to simulate the monochromatic wave process and its associated sediment dynamics.The adopted model is also firstly validated by laboratory experimental results as reported in this study.It is then used to examine the impacts of island morphological factors(island width,island height,island location and island side slope)on the island migration.The combined laboratory/physical and numerical experiment outputs suggest that reef islands can accrete vertically in response to the sea level rise and the increased storminess.展开更多
Changes in vegetation status generally also represents changes in the ecological health of islands and reefs(IRs).However,studies are limited of drivers and trends of vegetation change of Nansha Islands,China and how ...Changes in vegetation status generally also represents changes in the ecological health of islands and reefs(IRs).However,studies are limited of drivers and trends of vegetation change of Nansha Islands,China and how they relate to climate change and human activities.To resolve this limitation,we studied changes to the Normalized Difference Vegetation Index(NDVI)vegetation-greenness index for 22 IRs of Nansha Islands during normal and extreme conditions.Trends of vegetation greenness were analyzed using Sen's slope and Mann-Kendall test at two spatial scales(pixel and island),and driving factor analyses were performed by time-lagged partial correlation analyses.These were related to impacts from human activities and climatic factors under normal(temperature,precipitation,radiation,and Normalized Difference Built-up Index(NDBI))and extreme conditions(wind speed and latitude of IRs)from 2016 to 2022.Results showed:1)among the 22 IRs,NDVI increased/decreased significantly in 15/4 IRs,respectively.Huayang Reef had the highest NDVI change-rate(0.48%/mon),and Zhongye Island had the lowest(–0.29%/mon).Local spatial patterns were in one of two forms:dotted-form,and degradation in banded-form.2)Under normal conditions,human activities(characterized by NDBI)had higher impacts on vegetation-greenness than other factors.3)Under extreme conditions,wind speed(R^(2)=0.2337,P<0.05)and latitude(R^(2)=0.2769,P<0.05)provided limited explanation for changes from typhoon events.Our results provide scientific support for the sustainable development of Nansha Islands and the United Nations‘Ocean Decade’initiative.展开更多
A detailed survey of the reefs in the Nansha Islands＇ sea that are of strategic importance is conducive to their future development. In this study, a total of 50 Landsat 8 operational land imager（OLI） images were u...A detailed survey of the reefs in the Nansha Islands＇ sea that are of strategic importance is conducive to their future development. In this study, a total of 50 Landsat 8 operational land imager（OLI） images were used to analyze the geological features and spectral characteristics of the Nansha reefs. The exposed islands/sandbanks,reef flats and sub-tidal reefs were identified with the near-infrared band, the red and green bands, and the blue band, respectively. Based on the relationships among various characteristics and bands illustrated in the OLI images, the maximum between-cluster variance threshold algorithm（OTSU method） and the mathematical morphology were employed to extract characteristic parameters of the spatial geometry of the reefs from top to bottom, which were subsequently operated by a series of post-processing methods such as vectorization,simplification and topological analysis. Among the 132 standalone reefs and 16 atolls that are identified in the study, four reefs have yet to be named in the Standard Names of Various Islands in the South China Sea and the website Nansha Islands Online（http：//www.nansha.org/）. Another 24 ones are exposed to the atmosphere even during high tides. Taiping Island with an area of 0.57 km^2 represents the largest exposed geological feature. This study demonstrated the applicability of medium-resolution satellite images to derive the coral reef information effectively and thus provided information for the related departments that are responsible to manage the coast.An improved resolution of multispectral bands with the panchromatic band in higher spatial resolution（15 m for OLI image） is expected to provide an optimum satellite based approach to map marine habitats.展开更多
Under the background of vigorously developing facilities of island/reef in the world,the economic value and strategic significance of the island/reef have become increasingly important.Unfortunately,they may easily be...Under the background of vigorously developing facilities of island/reef in the world,the economic value and strategic significance of the island/reef have become increasingly important.Unfortunately,they may easily become the attacking target of missiles in the war time.Therefore,aiming at the damage quantification of the targets in the island/reef under the missile attacking,a macroscopic damage assessment model for the target area is proposed in this paper.The model focuses on the construction of the assessment model framework.Firstly,the analytic hierarchy process and the grey relational analysis are applied to measure the importance of each target in the region through four indicators of the target hazard,striking urgency,damage advantage and mission relevance,respectively.Secondly,based on the damage mechanism of shock wave and fragments to target,the corresponding damage model is established,and the damage grade of each target in the evaluated area is obtained according to the damage criteria and grading standard.Finally,the model obtains the overall damage grade of the target area by employing the fuzzy comprehensive evaluation method,with synthesizing the importance and the damage grade of each target.Through the verification of an example,it demonstrates the certain feasibility of the model and provides a certain basis and reference for the subsequent research.展开更多
Coral reefs in the Xisha Islands （also known as the Paracel Islands in English）, South China Sea, have experienced dramatic declines in coral cover. However, the current regional scale hard coral distribution of geo...Coral reefs in the Xisha Islands （also known as the Paracel Islands in English）, South China Sea, have experienced dramatic declines in coral cover. However, the current regional scale hard coral distribution of geomorphic and ecological zones, essential for reefs management in the context of global warming and ocean acidification, is not well documented. We analyzed data from field surveys, Landsat-8 and GF-1 images to map the distribution of hard coral within geomorphic zones and reef fiat ecological zones. In situ surveys conducted in June 2014 on nine reefs provided a complete picture of reef status with regard to live coral diversity, evenness of coral cover and reef health （live versus dead cover） for the Xisha Islands. Mean coral cover was 12.5% in 2014 and damaged reefs seemed to show signs of recovery. Coral cover in sheltered habitats such as lagoon patch reefs and biotic dense zones of reef flats was higher, but there were large regional differences and low diversity. In contrast, the more exposed reef slopes had high coral diversity, along with high and more equal distributions of coral cover. Mean hard coral cover of other zones was 〈10%. The total Xisha reef system was estimated to cover 1 060 km2, and the emergent reefs covered -787 km2. Hard corals of emergent reefs were considered to cover 97 km2. The biotic dense zone of the reef flat was a very common zone on all simple atolls, especially the broader northern reef flats. The total cover of live and dead coral can reach above 70% in this zone, showing an equilibrium between live and dead coral as opposed to coral and algae. This information regarding the spatial distribution of hard coral can support and inform the management of Xisha reef ecosystems.展开更多
Based on the remote sensing information feature of Nansha coral islets and reefs that controlled by the Nansha Islands local area's goological structure and growth law, by means of mathematical model and PC, the N...Based on the remote sensing information feature of Nansha coral islets and reefs that controlled by the Nansha Islands local area's goological structure and growth law, by means of mathematical model and PC, the Nansha Islands coral islets and reefs' top geological data' spatial distribution and local change trend are simulated by using the trend surface system on the remote sensing composite information, and an scientific interpretation and local comparison of Nansha coral islands and islets' spatial distribution feature are made.展开更多
It is exceedingly important to estimate the stability of coral reefs. In recent years, growing construction projects have been carried out on the reef flat in the South China Sea. As a special marine geotechnical medi...It is exceedingly important to estimate the stability of coral reefs. In recent years, growing construction projects have been carried out on the reef flat in the South China Sea. As a special marine geotechnical medium, it is made of the reef debris underwent overwhelmingly long geological age. Reefs grow thickly on the carbonate platform after the Late Oligocene and have five to six main sedimentary facies. It can be used as a recorder to measure the occurrence time of recent earthquake. A model of reef body is presented to study the influence of earthquakes according to the geological structure characteristic of reefs in the Nansha Islands. Furthermore, Geo Studio is used to simulate stress and deformation situations within it under various earthquake intensities. A safety factor is calculated by the limit equilibrium method, and the possible scenarios of earthquake-induced landslides and sliding scale are defined with a Newmark sliding block method, as well as stress distribution and deformation behaviors. Therefore, the numerical results suggest that the connections between the coral reef and the earthquake are as follows：（1） the reef body has a good stability under self-gravity state;（2） after the earthquake, it may cause slope＇s instability and bring out slumping when the safety factor is smaller than 1（FS〈1）;（3） the safety factor decreases with the increasing earthquake intensity, and fluctuates around a particular value after a while;and（4） as a new developed part of the reef, the smaller shallow landslide will be easily subject to collapse caused by the earthquake. It is concluded that it is feasible to provide a reference for evaluating the stability of coral reef using a geotechnical engineering simulation method. This can help the engineering constructions in the South China Sea.展开更多
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
Thick recent carbonate sediments cover all the intertidal and subtidal zones consist of mainly different shell and coral reef debris. The chemical investigations of the coral fragments were done on controlled bases, w...Thick recent carbonate sediments cover all the intertidal and subtidal zones consist of mainly different shell and coral reef debris. The chemical investigations of the coral fragments were done on controlled bases, which depend on the coral size and seasons, in order to elucidate the effect of weather parameters on the coral reefs. Geochemical investigation indicated that corals gathered from high-tide mark are mainly contaminated by copper, cobalt, and chromium and the corals gathered from low-tide mark are contaminated by lead and zinc. All the analyzed coral samples are contaminated by copper. The major contamination sights by heavy metals are related to the weather pattern around the islands. Calcium concentration in all the corals indicates a low-Magnesium calcite or aragonite composition, except for some coral samples which were gathered during October from the high-tide mark. Trace element concentration levels show high concentrations at sights of low-wave action around the island during the various seasons. Chemical analysis on the coral derbies indicates compositional variations regarding calcium and magnesium mole% between the seasons and at different locations and it is dependant on wind direction and water salinity. Some localities are iron rich others are aluminum and potassium rich. Generally, aluminum, iron, and potassium occur in lower quantities than the other elements. Therefore, all the chemical data regarding trace elements indicate relationship to weather and environmental parameters.展开更多
Harboring polyextremotolerant microbial topsoil communities,biological soil crusts(biocrusts)occur across various climatic zones,and have been well studied in the terrestrial drylands.However,little is known about the...Harboring polyextremotolerant microbial topsoil communities,biological soil crusts(biocrusts)occur across various climatic zones,and have been well studied in the terrestrial drylands.However,little is known about the functional metabolic potential of microbial communities involved in the biogeochemical processes during the early succession of biocrusts on the tropical reef islands.We collected 26 biocrusts and bare soil samples from the Xisha Islands and Nansha Islands,and applied a functional gene array(GeoChip 5.0)to reveal nitrogen(N)cycling processes involved in these samples.Both physicochemical measurement and enzyme activity assay were utilized to characterize the soil properties.Results revealed the composition of N-cycling functional genes in biocrusts was distinct from that in bare soil.Additionally,microorganisms in biocrusts showed lower functional potential related to ammonification,denitrification,N assimilation,nitrification,N fixation,and dissimilatory nitrate reduction to ammonium compared to bare soils.Although the abundance of nifH gene was lower in biocrusts,nitrogenase activity was significantly higher compared to that in bare soils.Precipitation,soil physicochemical properties(i.e.,soil available copper,soil ammonia N and pH)and soil biological properties(i.e.,β-glucosidase,fluorescein diacetate hydrolase,alkaline protease,urease,alkaline phosphatase,catalase and chlorophyll a)correlated to the N-cycling functional genes structure.Nitrate N and ammonia N were more abundant in biocrusts than bare soil,while pH value was higher in bare soil.Our results suggested biocrusts play an important role in N-cycling in coral sand soil,and will be helpful in understanding the development and ecological functions of biocrusts on tropical reef islands.展开更多
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
The Sagar Island,located north of the Bay of Bengal,intercepts the flow in the Hoogly estuary that comprises a network of several estuarine distributaries and creeks,which is considered to be one of the largest estuar...The Sagar Island,located north of the Bay of Bengal,intercepts the flow in the Hoogly estuary that comprises a network of several estuarine distributaries and creeks,which is considered to be one of the largest estuarine systems in the world.The Hooghly River experiences a tidal range in the order of about 4 m,due to which the tide-generated currents drive the sediments which are continuously set in motion.The temple,Kapil Muni(21°38'15.35"N,88°4'30.56"E)is located on the south-western side of Sagar Island,where an annual religious festival and rituals with about a million pilgrims is conducted.The pertinent erosion problem at a rate of about 5 m/year is prevalent at the site has considerably reduced the beach width,thereby,resulting in reduced space for religious as well as recreational activities along the coast.A novel cross-section for the proposed submerged reef using geosynthetic materials is designed considering the different sitespecific,environmental,and socio-economic conditions.The submerged reef can effectively be devised to redistribute the current circulation pattern and trap the sediment for beach restoration.The performance of such a structure depends on its geometrical and structural characteristics,the location of the reef(i.e.)the water depth at the toe,distance from the coastline,wave-structure interaction,sediment transport and local morpho dynamics.The aforesaid criteria were optimized using a numerical model which predicted the average residual velocity in the site to be in the order of about 1 m/s.Owing to logistical constraints geosynthetic materials had to be employed.The detailed design of such a system arrived through numerical modelling and field measurements are presented and discussed in this paper.展开更多
To solve the durability of island and reef concrete engineering in the harsh environment of high temperature,high salt,high humidity and windy,the strength grade of concrete and the type of corrosion inhibitor were us...To solve the durability of island and reef concrete engineering in the harsh environment of high temperature,high salt,high humidity and windy,the strength grade of concrete and the type of corrosion inhibitor were used as the influence factors,while the relative dynamic elastic modulus was used as the evaluation index.In addition,the law and time variability of the deterioration of concrete,the size effect,environmental similarity and the service life model were studied.The results showed that improving the strength grade of concrete could improve the durability of concrete,and corrosion inhibitor could slightly improve the durability of concrete.Time-varying law of the deterioration of concrete conformed to the univariate quadratic polynomial.Combined with the concrete damage equivalent theory,a size effect model based on the relative dynamic elastic modulus was proposed and verified,and the size effect coefficient was also given.An environmental similarity model between simulated and practical island and reef environment was proposed.Combined with the reliability theory and the first order second moment method,a new service life model of concrete structure was proposed.The authors were convinced that the research will be advantageous to researchers.展开更多
A study on the sedimentology of the Redang Island coral reefs environment was conducted. Sediments were collected on board UNIPERTAMA VII during the pre and post monsoon seasons. Twenty and seven sediments samples wer...A study on the sedimentology of the Redang Island coral reefs environment was conducted. Sediments were collected on board UNIPERTAMA VII during the pre and post monsoon seasons. Twenty and seven sediments samples were collected using a Smith McIntyre grab on board UNI PERTAMA VII and put in labelled plastic bags then brought back to the laboratory for analysis. The sediments were analyzed for their sedimentological characteristics （mean size, skewness, standard deviation and kurtosis） using dry sieving method. Results showed that the highest mean size value of the sediments during the pre and post monsoons seasons are 2.14 ~ and 2.37 O. respectively and the lowest are -0.40 q~ and -0.10 ~, respectively. Based on the results, sediments can be classified as medium sand （34%）, poorly sorted （67%）, strongly negative skewed （36%） and extremely leptokurtic （56%） during the pre monsoon season, while during the post monsoon season sediments can be classified as medium sand （38%）, poorly sorted （73%）, strongly negative skewed （41%） and very leptokurtic （62%）. Results revealed that the sediments in the whole study area are relatively coarse. No relationship was observed between mean size and other sedimentological characteristics （R2= 0.05 pre-monsoon. R2 =0.0017 post monsoon） with seasons.展开更多
Abstract: Based on the study of stratigraphy and fossils, the Early Permian ocean in eastern Kunlun is recognized as a kind of reef-island ocean, in which there exist many different kinds of sediment, including patch ...Abstract: Based on the study of stratigraphy and fossils, the Early Permian ocean in eastern Kunlun is recognized as a kind of reef-island ocean, in which there exist many different kinds of sediment, including patch carbonate platform, reef facies, transitional facies and deep basin sediments. It has been found that the total contents of REEs increase gradually from carbonate platform facies to deep basin facies. Meanwhile, sediments of different facies have different REE distribution patterns and different Ce anomalies. Most of the sediments of patch carbonate platform facies or reef facies are characterized by extremely negative Ce anomalies or moderately negative Ce anomalies (Ce/Ce*=0.33 to 0.55), and medium or thin-bedded limestones of transitional facies by moderately negative Ce anomalies (Ce/Ce*=0.49 to 0.60). However, sediments of deep basin facies show weak or no negative Ce anomalies (Ce/Ce*=0.69 to 1.47), among which the value of Ce/Ce* in the radiolarian chert is 1.47.展开更多
The migration and transformation of nitrogen(N)in sediments play an important role in regulating the N concentration and nutrient structures in shallow seas.However,studies of sedimentary N dynamics are rarely focused...The migration and transformation of nitrogen(N)in sediments play an important role in regulating the N concentration and nutrient structures in shallow seas.However,studies of sedimentary N dynamics are rarely focused on carbonate sediments,although these account for about 40%of the continental shelf area.Thus,the regulation mechanisms of the N dynamics in the carbonate sands of coral reefs are not clear.Taking the coral reef area of Weizhou Island,which has a relatively high N concentration,as the research object,we conducted a series of flow-through reactor experiments to investigate the fluxes of different N forms at the interface of sediment and seawater and their regulation mechanism by environmental factors.The fluxes of dissolved inorganic and organic N(DIN and DON)at different stations were-0.39-0.12 mmol/(m^(2)·h) and-0.18-0.39 mmol/(m^(2)·h),respectively.Denitrification(0.11-0.25 mmol/(m^(2)·h) was closely coupled to nitrification,which was limited by the availability of organic matter and its degradation product(i.e.,NH_(4)^(+)).Thus,the excessive NO_(3)^(-) might be reduced to NH4+by dissimilatory nitrate reduction to ammonium,rather than to N_(2) by denitrification.NO_(3)^(-) reduction peaked at intermediate advection rates(96 L/(m^(2)·h)) and flow path lengths(10 cm),but the release of DON also peaked at the same condition.In addition,climate warming would significantly affect sedimentary N dynamics at Weizhou Island.These results may help address the broader issue of the N cycle in coral reef eco systems under the dual pressure of climate warming and anthropogenic activities,and these results are beneficial to coral reef protection and local ecological management.展开更多
基金The National Natural Science Foundation of China under contract Nos 51979013 and 51909013the National Key Research and Development Program of China under contract Nos 2021YFC3100502 and 2021YFB2601105the Hainan Provincial Natural Science Foundation of China under contract No.421QN0978.
文摘The persistence and habitability of coral reef islands in future extreme oceanographic conditions has received increasing attention in the recent decade,concerning that the sea level rise(SLR)and more frequent and intense storms in the context of global climate change are expected to destabilize those islands.Here,we conduct a set of wave-flume laboratory experiments focusing on the morphodynamic change of reef islands to varying ocean forcing conditions(wave height and SLR).Subsequently,a phase-resolving XBeach numerical model is adopted to simulate the monochromatic wave process and its associated sediment dynamics.The adopted model is also firstly validated by laboratory experimental results as reported in this study.It is then used to examine the impacts of island morphological factors(island width,island height,island location and island side slope)on the island migration.The combined laboratory/physical and numerical experiment outputs suggest that reef islands can accrete vertically in response to the sea level rise and the increased storminess.
基金Under the auspices of National Key Research and Development Program of China (No.2022YFC3103103)。
文摘Changes in vegetation status generally also represents changes in the ecological health of islands and reefs(IRs).However,studies are limited of drivers and trends of vegetation change of Nansha Islands,China and how they relate to climate change and human activities.To resolve this limitation,we studied changes to the Normalized Difference Vegetation Index(NDVI)vegetation-greenness index for 22 IRs of Nansha Islands during normal and extreme conditions.Trends of vegetation greenness were analyzed using Sen's slope and Mann-Kendall test at two spatial scales(pixel and island),and driving factor analyses were performed by time-lagged partial correlation analyses.These were related to impacts from human activities and climatic factors under normal(temperature,precipitation,radiation,and Normalized Difference Built-up Index(NDBI))and extreme conditions(wind speed and latitude of IRs)from 2016 to 2022.Results showed:1)among the 22 IRs,NDVI increased/decreased significantly in 15/4 IRs,respectively.Huayang Reef had the highest NDVI change-rate(0.48%/mon),and Zhongye Island had the lowest(–0.29%/mon).Local spatial patterns were in one of two forms:dotted-form,and degradation in banded-form.2)Under normal conditions,human activities(characterized by NDBI)had higher impacts on vegetation-greenness than other factors.3)Under extreme conditions,wind speed(R^(2)=0.2337,P<0.05)and latitude(R^(2)=0.2769,P<0.05)provided limited explanation for changes from typhoon events.Our results provide scientific support for the sustainable development of Nansha Islands and the United Nations‘Ocean Decade’initiative.
基金The National High Technology Research and Development Program of China(863 Program)under contract No.2012AA12A406the National Natural Science Foundation of China under contract Nos 41471068,41171325,and J1103408+1 种基金the Program for New Century Excellent Talents in University under contract No.NCET-12-0264the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)
文摘A detailed survey of the reefs in the Nansha Islands＇ sea that are of strategic importance is conducive to their future development. In this study, a total of 50 Landsat 8 operational land imager（OLI） images were used to analyze the geological features and spectral characteristics of the Nansha reefs. The exposed islands/sandbanks,reef flats and sub-tidal reefs were identified with the near-infrared band, the red and green bands, and the blue band, respectively. Based on the relationships among various characteristics and bands illustrated in the OLI images, the maximum between-cluster variance threshold algorithm（OTSU method） and the mathematical morphology were employed to extract characteristic parameters of the spatial geometry of the reefs from top to bottom, which were subsequently operated by a series of post-processing methods such as vectorization,simplification and topological analysis. Among the 132 standalone reefs and 16 atolls that are identified in the study, four reefs have yet to be named in the Standard Names of Various Islands in the South China Sea and the website Nansha Islands Online（http：//www.nansha.org/）. Another 24 ones are exposed to the atmosphere even during high tides. Taiping Island with an area of 0.57 km^2 represents the largest exposed geological feature. This study demonstrated the applicability of medium-resolution satellite images to derive the coral reef information effectively and thus provided information for the related departments that are responsible to manage the coast.An improved resolution of multispectral bands with the panchromatic band in higher spatial resolution（15 m for OLI image） is expected to provide an optimum satellite based approach to map marine habitats.
文摘Under the background of vigorously developing facilities of island/reef in the world,the economic value and strategic significance of the island/reef have become increasingly important.Unfortunately,they may easily become the attacking target of missiles in the war time.Therefore,aiming at the damage quantification of the targets in the island/reef under the missile attacking,a macroscopic damage assessment model for the target area is proposed in this paper.The model focuses on the construction of the assessment model framework.Firstly,the analytic hierarchy process and the grey relational analysis are applied to measure the importance of each target in the region through four indicators of the target hazard,striking urgency,damage advantage and mission relevance,respectively.Secondly,based on the damage mechanism of shock wave and fragments to target,the corresponding damage model is established,and the damage grade of each target in the evaluated area is obtained according to the damage criteria and grading standard.Finally,the model obtains the overall damage grade of the target area by employing the fuzzy comprehensive evaluation method,with synthesizing the importance and the damage grade of each target.Through the verification of an example,it demonstrates the certain feasibility of the model and provides a certain basis and reference for the subsequent research.
基金Supported by the National High Technology Research and Development Program of China(863 Program)(No.2012AA12A406)the National Natural Science Foundation of China(No.41271409)the National Science and Technology Major Project(No.00-Y30B15-9001-14/16-5)
文摘Coral reefs in the Xisha Islands （also known as the Paracel Islands in English）, South China Sea, have experienced dramatic declines in coral cover. However, the current regional scale hard coral distribution of geomorphic and ecological zones, essential for reefs management in the context of global warming and ocean acidification, is not well documented. We analyzed data from field surveys, Landsat-8 and GF-1 images to map the distribution of hard coral within geomorphic zones and reef fiat ecological zones. In situ surveys conducted in June 2014 on nine reefs provided a complete picture of reef status with regard to live coral diversity, evenness of coral cover and reef health （live versus dead cover） for the Xisha Islands. Mean coral cover was 12.5% in 2014 and damaged reefs seemed to show signs of recovery. Coral cover in sheltered habitats such as lagoon patch reefs and biotic dense zones of reef flats was higher, but there were large regional differences and low diversity. In contrast, the more exposed reef slopes had high coral diversity, along with high and more equal distributions of coral cover. Mean hard coral cover of other zones was 〈10%. The total Xisha reef system was estimated to cover 1 060 km2, and the emergent reefs covered -787 km2. Hard corals of emergent reefs were considered to cover 97 km2. The biotic dense zone of the reef flat was a very common zone on all simple atolls, especially the broader northern reef flats. The total cover of live and dead coral can reach above 70% in this zone, showing an equilibrium between live and dead coral as opposed to coral and algae. This information regarding the spatial distribution of hard coral can support and inform the management of Xisha reef ecosystems.
文摘Based on the remote sensing information feature of Nansha coral islets and reefs that controlled by the Nansha Islands local area's goological structure and growth law, by means of mathematical model and PC, the Nansha Islands coral islets and reefs' top geological data' spatial distribution and local change trend are simulated by using the trend surface system on the remote sensing composite information, and an scientific interpretation and local comparison of Nansha coral islands and islets' spatial distribution feature are made.
基金The National Basic Research Program(973 Program)of China under contract No.2013CB956104the National Natural Science Foundation of China under contract No.41376063the Strategic Priority Research Program of the Chinese Academy of Sciences under contract No.XDA13000000
文摘It is exceedingly important to estimate the stability of coral reefs. In recent years, growing construction projects have been carried out on the reef flat in the South China Sea. As a special marine geotechnical medium, it is made of the reef debris underwent overwhelmingly long geological age. Reefs grow thickly on the carbonate platform after the Late Oligocene and have five to six main sedimentary facies. It can be used as a recorder to measure the occurrence time of recent earthquake. A model of reef body is presented to study the influence of earthquakes according to the geological structure characteristic of reefs in the Nansha Islands. Furthermore, Geo Studio is used to simulate stress and deformation situations within it under various earthquake intensities. A safety factor is calculated by the limit equilibrium method, and the possible scenarios of earthquake-induced landslides and sliding scale are defined with a Newmark sliding block method, as well as stress distribution and deformation behaviors. Therefore, the numerical results suggest that the connections between the coral reef and the earthquake are as follows：（1） the reef body has a good stability under self-gravity state;（2） after the earthquake, it may cause slope＇s instability and bring out slumping when the safety factor is smaller than 1（FS〈1）;（3） the safety factor decreases with the increasing earthquake intensity, and fluctuates around a particular value after a while;and（4） as a new developed part of the reef, the smaller shallow landslide will be easily subject to collapse caused by the earthquake. It is concluded that it is feasible to provide a reference for evaluating the stability of coral reef using a geotechnical engineering simulation method. This can help the engineering constructions in the South China Sea.
基金Under the auspices of National Natural Science Foundation of China(No.41530962)
文摘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.
文摘Thick recent carbonate sediments cover all the intertidal and subtidal zones consist of mainly different shell and coral reef debris. The chemical investigations of the coral fragments were done on controlled bases, which depend on the coral size and seasons, in order to elucidate the effect of weather parameters on the coral reefs. Geochemical investigation indicated that corals gathered from high-tide mark are mainly contaminated by copper, cobalt, and chromium and the corals gathered from low-tide mark are contaminated by lead and zinc. All the analyzed coral samples are contaminated by copper. The major contamination sights by heavy metals are related to the weather pattern around the islands. Calcium concentration in all the corals indicates a low-Magnesium calcite or aragonite composition, except for some coral samples which were gathered during October from the high-tide mark. Trace element concentration levels show high concentrations at sights of low-wave action around the island during the various seasons. Chemical analysis on the coral derbies indicates compositional variations regarding calcium and magnesium mole% between the seasons and at different locations and it is dependant on wind direction and water salinity. Some localities are iron rich others are aluminum and potassium rich. Generally, aluminum, iron, and potassium occur in lower quantities than the other elements. Therefore, all the chemical data regarding trace elements indicate relationship to weather and environmental parameters.
基金The Strategic Priority Research Program of the Chinese Academy of Sciences under contract Nos XDA13020301 and XDA13010500the Fund of Innovation Academy of South China Sea Ecology and Environmental EngineeringChinese Academy of Sciences under contract No.ISEE2018PY01。
文摘Harboring polyextremotolerant microbial topsoil communities,biological soil crusts(biocrusts)occur across various climatic zones,and have been well studied in the terrestrial drylands.However,little is known about the functional metabolic potential of microbial communities involved in the biogeochemical processes during the early succession of biocrusts on the tropical reef islands.We collected 26 biocrusts and bare soil samples from the Xisha Islands and Nansha Islands,and applied a functional gene array(GeoChip 5.0)to reveal nitrogen(N)cycling processes involved in these samples.Both physicochemical measurement and enzyme activity assay were utilized to characterize the soil properties.Results revealed the composition of N-cycling functional genes in biocrusts was distinct from that in bare soil.Additionally,microorganisms in biocrusts showed lower functional potential related to ammonification,denitrification,N assimilation,nitrification,N fixation,and dissimilatory nitrate reduction to ammonium compared to bare soils.Although the abundance of nifH gene was lower in biocrusts,nitrogenase activity was significantly higher compared to that in bare soils.Precipitation,soil physicochemical properties(i.e.,soil available copper,soil ammonia N and pH)and soil biological properties(i.e.,β-glucosidase,fluorescein diacetate hydrolase,alkaline protease,urease,alkaline phosphatase,catalase and chlorophyll a)correlated to the N-cycling functional genes structure.Nitrate N and ammonia N were more abundant in biocrusts than bare soil,while pH value was higher in bare soil.Our results suggested biocrusts play an important role in N-cycling in coral sand soil,and will be helpful in understanding the development and ecological functions of biocrusts on tropical reef islands.
基金The National Key Research and Development Program of China under contract No.2018YFC1406502the National Natural Science Foundation of China under contract No.31902374+1 种基金the Key Special Project for Introduced Talents Team of Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou)under contract No.GML2019ZD0605the Central Public-Interest Scientific Institution Basal Research Fund of Chinese Academy of Fishery Sciences under contract No.2020TD05.
文摘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.
文摘The Sagar Island,located north of the Bay of Bengal,intercepts the flow in the Hoogly estuary that comprises a network of several estuarine distributaries and creeks,which is considered to be one of the largest estuarine systems in the world.The Hooghly River experiences a tidal range in the order of about 4 m,due to which the tide-generated currents drive the sediments which are continuously set in motion.The temple,Kapil Muni(21°38'15.35"N,88°4'30.56"E)is located on the south-western side of Sagar Island,where an annual religious festival and rituals with about a million pilgrims is conducted.The pertinent erosion problem at a rate of about 5 m/year is prevalent at the site has considerably reduced the beach width,thereby,resulting in reduced space for religious as well as recreational activities along the coast.A novel cross-section for the proposed submerged reef using geosynthetic materials is designed considering the different sitespecific,environmental,and socio-economic conditions.The submerged reef can effectively be devised to redistribute the current circulation pattern and trap the sediment for beach restoration.The performance of such a structure depends on its geometrical and structural characteristics,the location of the reef(i.e.)the water depth at the toe,distance from the coastline,wave-structure interaction,sediment transport and local morpho dynamics.The aforesaid criteria were optimized using a numerical model which predicted the average residual velocity in the site to be in the order of about 1 m/s.Owing to logistical constraints geosynthetic materials had to be employed.The detailed design of such a system arrived through numerical modelling and field measurements are presented and discussed in this paper.
基金supported by the National Natural Science Foundation of China(Grant Nos.51878350 and 11832013).
文摘To solve the durability of island and reef concrete engineering in the harsh environment of high temperature,high salt,high humidity and windy,the strength grade of concrete and the type of corrosion inhibitor were used as the influence factors,while the relative dynamic elastic modulus was used as the evaluation index.In addition,the law and time variability of the deterioration of concrete,the size effect,environmental similarity and the service life model were studied.The results showed that improving the strength grade of concrete could improve the durability of concrete,and corrosion inhibitor could slightly improve the durability of concrete.Time-varying law of the deterioration of concrete conformed to the univariate quadratic polynomial.Combined with the concrete damage equivalent theory,a size effect model based on the relative dynamic elastic modulus was proposed and verified,and the size effect coefficient was also given.An environmental similarity model between simulated and practical island and reef environment was proposed.Combined with the reliability theory and the first order second moment method,a new service life model of concrete structure was proposed.The authors were convinced that the research will be advantageous to researchers.
文摘A study on the sedimentology of the Redang Island coral reefs environment was conducted. Sediments were collected on board UNIPERTAMA VII during the pre and post monsoon seasons. Twenty and seven sediments samples were collected using a Smith McIntyre grab on board UNI PERTAMA VII and put in labelled plastic bags then brought back to the laboratory for analysis. The sediments were analyzed for their sedimentological characteristics （mean size, skewness, standard deviation and kurtosis） using dry sieving method. Results showed that the highest mean size value of the sediments during the pre and post monsoons seasons are 2.14 ~ and 2.37 O. respectively and the lowest are -0.40 q~ and -0.10 ~, respectively. Based on the results, sediments can be classified as medium sand （34%）, poorly sorted （67%）, strongly negative skewed （36%） and extremely leptokurtic （56%） during the pre monsoon season, while during the post monsoon season sediments can be classified as medium sand （38%）, poorly sorted （73%）, strongly negative skewed （41%） and very leptokurtic （62%）. Results revealed that the sediments in the whole study area are relatively coarse. No relationship was observed between mean size and other sedimentological characteristics （R2= 0.05 pre-monsoon. R2 =0.0017 post monsoon） with seasons.
文摘Abstract: Based on the study of stratigraphy and fossils, the Early Permian ocean in eastern Kunlun is recognized as a kind of reef-island ocean, in which there exist many different kinds of sediment, including patch carbonate platform, reef facies, transitional facies and deep basin sediments. It has been found that the total contents of REEs increase gradually from carbonate platform facies to deep basin facies. Meanwhile, sediments of different facies have different REE distribution patterns and different Ce anomalies. Most of the sediments of patch carbonate platform facies or reef facies are characterized by extremely negative Ce anomalies or moderately negative Ce anomalies (Ce/Ce*=0.33 to 0.55), and medium or thin-bedded limestones of transitional facies by moderately negative Ce anomalies (Ce/Ce*=0.49 to 0.60). However, sediments of deep basin facies show weak or no negative Ce anomalies (Ce/Ce*=0.69 to 1.47), among which the value of Ce/Ce* in the radiolarian chert is 1.47.
基金The Guangxi Natural Science Foundation under contract Nos 2019GXNSFAA185001 and 2019GXNSFAA185022the National Natural Science Foundation of China under contract Nos 41976059 and 42166002.
文摘The migration and transformation of nitrogen(N)in sediments play an important role in regulating the N concentration and nutrient structures in shallow seas.However,studies of sedimentary N dynamics are rarely focused on carbonate sediments,although these account for about 40%of the continental shelf area.Thus,the regulation mechanisms of the N dynamics in the carbonate sands of coral reefs are not clear.Taking the coral reef area of Weizhou Island,which has a relatively high N concentration,as the research object,we conducted a series of flow-through reactor experiments to investigate the fluxes of different N forms at the interface of sediment and seawater and their regulation mechanism by environmental factors.The fluxes of dissolved inorganic and organic N(DIN and DON)at different stations were-0.39-0.12 mmol/(m^(2)·h) and-0.18-0.39 mmol/(m^(2)·h),respectively.Denitrification(0.11-0.25 mmol/(m^(2)·h) was closely coupled to nitrification,which was limited by the availability of organic matter and its degradation product(i.e.,NH_(4)^(+)).Thus,the excessive NO_(3)^(-) might be reduced to NH4+by dissimilatory nitrate reduction to ammonium,rather than to N_(2) by denitrification.NO_(3)^(-) reduction peaked at intermediate advection rates(96 L/(m^(2)·h)) and flow path lengths(10 cm),but the release of DON also peaked at the same condition.In addition,climate warming would significantly affect sedimentary N dynamics at Weizhou Island.These results may help address the broader issue of the N cycle in coral reef eco systems under the dual pressure of climate warming and anthropogenic activities,and these results are beneficial to coral reef protection and local ecological management.
