Optimization of Groundwater Pumping on Coral Islands Through the Application of Artificial Neural Network

The development and growing population has resulted in the increasing demand for potable water in tiny atolls of Lakshadweep group,off the western coast of India.In recent years,the groundwater quality,in such atolls,has been deteriorated due to indiscriminate exploitation of groundwater to meet the demand.Thus arranging a sustainable supply of groundwater has become the most challenging task on these tiny atolls for the survival of human life. Groundwater floats in the form of thin lens,which

Remote sensing composite information's trend surface analysis of Nansha Islands coral islets and reefs' top

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.

Reconstructing Environmental Changes of a Coastal Lagoon with Coral Reefs in Southeastern Hainan Island

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.

The Effect of Climate on the Chemical Composition of the Coral Reefs around Kubbar Island—Kuwait

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.

Diversity of symbiotic algae of the genus Symbiodinium in scleractinian corals of the Xisha Islands in the South China Sea

Symbiotic algae （Symbiodinium sp.） in scleractinian corals are important in understanding how coral reefs will respond to global climate change. The present paper reports on the diversity of Symbiodinium sp. in 48 scleractinian coral species from 25 genera and 10 families sampled from the Xisha Islands in the South China Sea, which were identified with the use of restriction fragment length polymorphism （RFLP） of the nuclear ribosomal DNA large subunit gene （rDNA）. The results showed that： （i） Symbiodinium Clade C was the dominant zooxanthellae in scleractinian corals in the Xisha Islands; （ii） Symbiodinium Clade D was found in the corals Montipora aequituberculata, Galaxea fascicularis, and Plerogyra sinuosa; and （iii） both Symbiodinium Clades C and D were found simultaneously in Montipora digitata, Psammocora contigua, and Galaxeafascicularis. A poor capacity for symbiosis polymorphism, as uncovered by RFLP, in the Xisha Islands indicates that the scleractinian corals have low adaptability to environmental changes. Further studies are needed to investigate zooxanthellae diversity using other molecular markers.

Survey of reefs based on Landsat 8 operational land imager(OLI)images in the Nansha Islands, South China Sea

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.

TYPE AND EVOLUTION OF LANDSCAPES OF NANSHA ISLANDS

Landscapes of the Nansha Islands may be divided into five types: tropical marine organismbreeding landscape of reef knoll like Zengmu Shoal, Wan'an Bank and so on; tropical marine organismbreeding landscape of atoll including all emerged reefs and most submerged reefs; tropical evergreen arborbush forest and phosphorous lime soil landscape of limesand Islets like Taiping Islet, Nanwei islet and so on; tropical shallow sea marine organismbreeding landscape of southern continental shelf; tropical oceanic and deepsea marine organism landscape in middle and north parts of the Nansha Islands area. These five landscape types may be also summed up as two categories, one is tropical sea landscape including those in shallow and deep sea, the other is tropical coral reef landscape including those of reef knoll, atoll and limesand islet. This paper outlines the evolutional model of landscapes of the Nansha Islands. The distribution and evolution of landscape types are related with palaeogeography and modern environmental conditions. The former shallow sea of the Nansha islands was coastal zone in the Late Pleistocene epoch. Deep sea is evolved from shallow sea due to long and slow subsidence of crust. Modern coral reefs develop on old reef top of the Late pleistocene epoch or on baserock of continental shelf in the Holocene due to the rise of sea level in postglacial. Limesand islet is in the peak of developmental stage.

El Ni?o/Southern Oscillation during the 4.2 ka event recorded by growth rates of corals from the North South China Sea

The 4.2 ka event that occurred during the period from 4 500–3 900 a BP was characterized by cold and dry climates and resulted in the collapse of civilizations around the world. The cause of this climatic event, however, has been under debate. We collected four corals(Porites lutea) from Yongxing Island, Xisha Islands, South China Sea, dated them with the U-series method, and measured the annual coral growth rates using X-ray technology. The dating results showed that the coral growth ages were from 4 500–3 900 a BP, which coincide well with the period of the4.2 ka event. We then reconstructed annual sea surface temperature anomaly(SSTA) variations based on the coral growth rates. The growth rate-based SSTA results showed that the interdecadal SSTA from 4 500–3 900 a BP was lower than that during modern times(1961–2008 AD). A spectral analysis showed that the SSTA variations from4 500–3 900 a BP were under the influence of El Nino-Southern Oscillation(ENSO) activities. From 4 500–4 100 a BP, the climate exhibited La Nina-like conditions with weak ENSO intensity and relatively stable and lower SSTA amplitudes. From 4 100–3 900 a BP, the climate underwent a complicated period of ENSO variability and showed alternating El Nino-or La Nina-like conditions at interdecadal time scales and large SSTA amplitudes. We speculate that during the early and middle stages of the 4.2 ka event, the cold climate caused by weak ENSO activities largely weakened social productivity. Then, during the end stages of the 4.2 ka event, the repeated fluctuations in the ENSO intensity caused frequent extreme weather events, resulting in the collapse of civilizations worldwide. Thus, the new evidence obtained from our coral records suggests that the 4.2 ka event as well as the related collapse of civilizations were very likely driven by ENSO variability.

The research on the remote sensing＇s information tree model of the Nansha coral islets and reef＇s spatial structure

Based on the Nansha coral islets and reef's time-space attributes,and the intension and extension of the remote sensing information, the concept model and concept system of coral islets and reef are proposed.Then twin-tree remote sensing information model for different kinds of reef is constructed by using abstracted islets and reef's primitive, and the structure recognition system for coral islets and reef type is developed.

《西沙群岛珊瑚岛(礁)地区岩土工程勘察标准》研究与编制

为适应和满足西沙群岛珊瑚岛(礁)工程建设的需要,使珊瑚岛(礁)岩土工程勘察有据可依,总结了西沙群岛岩土工程勘察项目实践经验和研究成果,通过资料收集、分析与研究,编制了《西沙群岛珊瑚岛(礁)地区岩土工程勘察标准》(DBJ46—060—2022)。介绍标准的编制背景、编制的工作流程、标准的主要内容和重点研究内容,探讨需要进一步研究的内容。

三亚凤凰岛造礁石珊瑚迁移效果研究

造礁石珊瑚既是构成珊瑚礁生态系统中的关键功能生物,也是国家二级保护野生动物,其数量的快速衰退已引起了广泛关注,因此近年来我国对造礁石珊瑚以及珊瑚礁生态系统的保护正在逐步加强。海岸工程易对周边的珊瑚礁造成严重影响,实施保护性迁移是降低工程对造礁石珊瑚影响的重要手段。为研究海南热带海域造礁石珊瑚迁移方法以及迁移保护的效果,我们对三亚凤凰岛二期项目拆除工程影响海域内的造礁石珊瑚实施了保护性迁移及监测。迁移造礁石珊瑚个体共计16634株,包括鹿角珊瑚属、牡丹珊瑚属、滨珊瑚属等18属造礁石珊瑚种类。迁移个体分别迁移至鹿回头海域6210株与西岛海域10424株。迁移珊瑚采用了三种移植方法,分别为铆钉移植、小型移植礁体移植与直接摆放。在迁移至鹿回头和西岛两地8个月后,迁移珊瑚平均存活率均在80%以上,两地迁移珊瑚的总存活率为86.24%。调查的结果显示,铆钉移植的方法存活率最高,小型移植礁体和直接摆放的两种移植方法存活率稍低。迁移至西岛的珊瑚8个月平均生长了3.03cm,的增长率为23.31%,而鹿回头迁入的珊瑚平均生长了6.15cm,增长率为58.74%,高于迁移至西岛的珊瑚。迁移采用的三种移植方法的8个月的存活率均高于75%,并且珊瑚的生长速率较好,说明珊瑚适应迁入区环境。由以上结果来看,此次保护性迁移珊瑚数量多,涉及的珊瑚种类广,在迁移后经受过两次台风的影响,迁移结果具有一定的代表性。本研究中,珊瑚迁移的效果达到了保护受拆除工程影响的造礁石珊瑚的目的,可为未来的珊瑚迁移性保护提供重要经验。

硫酸锌胶结珊瑚砂渗透特性试验及工程应用探讨

对松散珊瑚砂进行胶结处理以降低岛礁地层渗透性是促进生态岛淡水涵养的重要手段之一。为此,开展了硫酸锌胶结珊瑚砂的渗透试验,分析了不同浸泡时长、硫酸锌溶液浓度及初始干密度对胶结珊瑚砂渗透性的影响,采用干湿循环试验验证其耐久性,通过X射线衍射(X-ray diffraction,简称XRD)、扫描电镜(scanning electron microscope,简称SEM)、能量色散X射线光谱(energy dispersive spectrometer,简称EDS)及计算机断层扫描(computed tomography,简称CT)扫描研究微观胶结机制。结果表明:(1)硫酸锌胶结可将珊瑚砂渗透系数降低70.17%~95.79%;(2)干湿循环16次后,胶结处理36 h的珊瑚砂样品质量损失率不超过4%,渗透系数变化不超过1.0×10^(-3)cm/s,表明样品耐久性良好;(3)珊瑚砂和硫酸锌反应生成二水石膏与菱锌矿填充样品孔隙,使孔喉平均半径、配位数均减小,孔隙连通性显著下降。该技术可应用于岛礁吹填初期固砂防侵蚀、提高地基承载力、降低渗透性以促进地下淡水涵养和生态岛建设,具有重要的工程应用价值。

珊瑚礁海岸沉积物输运及珊瑚砂岛演变研究综述

珊瑚礁海岸沉积物的输运及珊瑚砂岛的演变研究在我国起步较晚,同时南中国海的珊瑚砂岛是我国重要的海洋空间资源,涉及国家领土主权的核心利益,开展这方面研究具有重要的学术价值和现实意义。综合分析了推移质和悬移质碳酸盐沉积物输运过程及其影响因素,重点介绍了短波、低频长波和海流对沉积物输运的驱动机制,以及粗糙珊瑚对沉积物的遮蔽效应。总结分析了珊瑚砂岛的动态演变规律及其影响因素,并重点介绍了珊瑚砂岛在长期海平面上升和短期风暴潮增强时的演变规律,并提出了今后研究需要关注的方向。

南海西沙典型珊瑚砂岛礁场地地震响应模拟与监测研究

南海珊瑚砂岛礁场地的非线性地震响应分析对中国南海岛礁建设的地震安全保障具有重要现实意义。以南海西沙某典型珊瑚砂岛礁为研究对象,建立了考虑该岛礁场地地形地貌特征及非饱和带水文地质特征的岛礁场地地震响应分析二维有限元数值模型。基于南海岛礁现场监测地震数据验证了模型的有效性,数值分析了不同输入地震信号的岛礁场地非线性地震响应规律。结果表明:①受岛礁岩盆效应影响,岛礁边缘处的PGA放大效应较为显著;沿高程方向,受地层岩性变化及地下水饱和度的影响,PGA放大因子曲线表现出明显的界面转折特征,并且松散珊瑚砂层的PGA放大效应较基岩更为显著;②岛礁场地加速度反应谱的卓越周期与输入地震动基本吻合,但岛礁场地的地表地震动显著持时与输入地震动相比均有不同幅度的延长;③全饱和与否对PGA放大因子和Arias强度有一定影响,但对PSA反应谱影响较小。研究成果可为南海西沙类似珊瑚砂岛礁场地的地震安全研究及场地抗震提供参考。

中国热带珊瑚岛优势木本植物抗风桐和草海桐的水分适应策略解析

植物水力性状能够反映植物对不同水分条件的适应能力,研究热带珊瑚岛特殊生境下优势植物的水力功能特征对深入理解热带珊瑚岛植物的水分适应策略,从而选择热带珊瑚岛植被构建和恢复的适生物种具有重要意义。该研究以中国热带珊瑚岛生境中2种优势适生木本植物:抗风桐(Pisonia grandis)和草海桐(Scaevola sericea)为研究对象,比较了其叶片和枝条的水力性状,并分析了其水分适应策略。结果表明,抗风桐的叶片栓塞抗性、枝条边材比导水率和叶片膨压丧失点显著高于草海桐,而枝条栓塞抗性、叶片导水率、边材密度和叶面积边材面积比均显著低于草海桐。抗风桐的叶片具有比枝条更强的抗栓塞能力,对水分胁迫敏感,但同时选择以高效的枝干水分运输来满足叶片高蒸腾需求的充足供水。草海桐枝条与叶片则存在水力脆弱性分区,在面临水分胁迫时叶片充当“安全阀”以保证枝干木质部的水力安全。抗风桐与草海桐能够通过协调叶片与枝条水力性状采取不同的水分适应策略,从而更好地适应热带珊瑚岛的特殊生境。

西沙群岛玉琢礁珊瑚礁鱼类种类组成及演变

玉琢礁是西沙群岛中的重要环礁,拥有多样化的珊瑚礁生态系统和丰富的鱼类资源。为掌握玉琢礁珊瑚礁鱼类的资源状况及其演变特征,于2023年采用手钓、水下潜捕、水下视频和eDNA等方法,对其珊瑚礁鱼类资源进行调查。共发现鱼类220种,其中eDNA方法共发现鱼类111种,结合2003年中国水产科学研究院南海水产研究所的历史档案数据,截至目前在玉琢礁共发现鱼类265种,隶属于12目50科128属,其中鲈形目占绝对优势。鱼类群落组成以小型鱼类为主,平均分类差异指数(Δ^(+))和变异分类差异指数(Λ^(+))分别为56.08和122.4;相似性分析表明,2003与2023年之间,鱼类在种类组成、食性组成和不同体型层面的相似性均表现为不相似或极不相似。与历史调查数据进行比较,共有45种鱼类未被监测到,其中大型肉食性鱼类受到自然与人类扰动的影响最为显著,植食性鱼类所受到的影响相对较小,分类多样性指数(Δ^(+)、Λ^(+))显著下降。初步推断不可持续的捕捞、生境衰退和温度上升等因素导致了玉琢礁珊瑚礁鱼类的更替。研究结果可为玉琢礁的珊瑚礁鱼类资源保护与管理、珊瑚礁生态系统的恢复提供参考。

吹填珊瑚礁岛地下水淡化时空规律初探

为分析吹填珊瑚礁岛地下水的时空淡化规律,开展珊瑚礁岛地下水现场长期监测,获取了不同位置、不同深度地下水电导率的长期监测数据和定期取样测试核验数据;结合礁岛降雨监测资料,以电导率为地下水质评价的主要指标,分析地下水电导率在时间、空间尺度上的变化特征,探索礁岛地下水的淡化趋势及影响因素,通过随机森林模型进一步预测了钻孔内地下水电导率的变化规律。研究结果表明,珊瑚礁岛地下水电导率总体呈震荡下降趋势,地下水电导率与时间的关系可以用指数函数表示。地下水电导率随深度的增加而增大直至与海水的电导率相当后维持稳定,礁岛内相同深度地下水电导率呈现中间低、四周高的趋势。说明地下水的淡化从礁岛中心部位开始向四周延展,并发现在礁岛中部存在多个初始淡化中心点。地下水电导率受降雨入渗、潮汐作用、水文地质参数等多个因素的影响,随机森林模型预测5 a后潜水面下8 m处的电导率将逐渐稳定在10000μS/cm,地下水的淡化速率显著降低。

间断级配珊瑚砂地基渗流侵蚀稳定性试验研究

为解决降雨入渗导致的岛礁珊瑚砂地基沉降、塌陷等渗流侵蚀问题,利用自制渗透仪对不同D_(15)/d_(85)(D_(15)为粗粒组中小于某粒径的土颗粒累计百分含量为15%所对应的颗粒粒径,d_(85)为细粒组中小于某粒径的土颗粒累计百分含量为85%所对应的粒径)和细颗粒含量的间断级配珊瑚砂开展自上而下的单向渗透试验,厘清细颗粒迁移特征和流失的基本条件,揭示珊瑚砂渗透性变化规律,并借助微观手段对其内在机制进行分析。结果表明:(1)对于土骨架粒径为2~10 mm的珊瑚砂而言,粒径为0.25~0.50 mm的粒组是保证其渗流侵蚀稳定的关键粒组;(2)间断级配珊瑚砂地基D_(15)/d_(85)比值小于10且细颗粒含量在20%~30%之间时,渗流侵蚀稳定性较好;(3)与石英砂相比,珊瑚砂特殊的矿物成分及颗粒形貌导致其更难发生颗粒迁移,抗渗流侵蚀能力更强;(4)工程实践中,可通过提高相对密实度、优化颗粒级配或采取注浆胶结等措施提高地基渗流侵蚀稳定性。研究结果可为岛礁地基抗渗流侵蚀设计提供科学依据。

西沙群岛浪花礁珊瑚礁鱼类种类组成与演替

为明确西沙群岛浪花礁鱼类物种组成,揭示鱼类演变特征,保护和合理利用西沙群岛珊瑚礁鱼类,于2023年通过潜水捕捞、手钓、水下视频以及eDNA等手段对浪花礁珊瑚礁鱼类进行调查研究,并结合1979年、1998—1999年及2003年的历史数据,解析浪花礁鱼类种类组成及变化情况。截至目前浪花礁共发现鱼类259种,隶属12个目47科115属,其中鲈形目鱼类最多,为200种。结果显示:(1)浪花礁鱼类物种数与其对应的最大全长成指数相关,物种数随最大全长增加而显著减少,并且浪花礁以小型鱼类和肉食性鱼类占据主导地位,分别占总种类数的49.03%和59.07%;(2)2023年的调查结果较历史数据共有77种鱼类近年未发现,以肉食性最多,而大型鱼类几乎全为肉食性鱼类,并且7种位列于国际自然及自然资源保护联盟(International Union for Conservation of Nature,IUCN)红色名录的鱼类均为大型鱼类,除了棕点石斑鱼(Epinephelus fuscoguttatus),其他在本研究均未发现;(3)浪花礁鱼类在种类组成、食性组成及不同体型层面较历史的相似性指数均不相似甚至极不相似,尤其是大型鱼类和肉食性鱼类的相似度最低;(4)平均分类差异指数(Δ^(+))和变异分类差异指数(Λ^(+))呈下降趋势,降幅明显并低于95%置信区间。以上结果表明,浪花礁环境受到扰动,气候变化和人类干扰等多重压力导致浪花礁鱼类组成发生显著更替,大型肉食性鱼类所受影响最为显著。本研究为浪花礁珊瑚礁生态系统的深层理解和有效管理与保护提供了理论参考,为珊瑚礁生态系统的修复提供了基础数据和科学依据。