ESR DATING OF CORAL REEFS IN THE SOUTH CHINA SEA

ESR dating of aragonitic and calcitic corals , eolianite , calcrete , and corallineae from coral reefs in the South China Sea was applied to study of Quaternary reef geology . The ESR ages of calcitic corals correlated with the biostratigraphy , lithostratigraphy and geochemistry of Well Xi-Chen-1 and the oxygen-isotope stratigraphy of deep sea sediments, were reliable and up to 1.26 Ma. The selection of signals for dating and other related problems are discussed .

Trace metal anomalies in bleached Porites coral at Meiji Reef, tropical South China Sea

Coral bleaching has generally been recognized as the main reason for tropical coral reef degradation, but there are few long-term records of coral bleaching events. In this study, trace metals including chromium(Cr), copper(Cu), molybdenum(Mo), manganese(Mn), lead(Pb), tin(Sn), titanium(Ti), vanadium(V), and yttrium(Y), were analyzed in two Porites corals collected from Meiji Reef in the tropical South China Sea(SCS) to assess differences in trace metal concentrations in bleached compared with unbleached coral growth bands. Ti, V, Cr, and Mo generally showed irregular fluctuations in both corals. Bleached layers contained high concentrations of Mn, Cu, Sn, and Pb. Unbleached layers showed moderately high concentrations of Mn and Cu only. The different distribution of trace metals in Porites may be attributable to different selectivity on the basis of vital utility or toxicity. Ti, V, Cr, and Mo are discriminated against by both coral polyps and zooxanthellae, but Mn, Cu, Sn, and Pb are accumulated by zooxanthellae and only Mn and Cu are accumulated by polyps as essential elements. The marked increase in Cu, Mn, Pb, and Sn are associated with bleaching processes, including mucus secretion, tissue retraction, and zooxanthellae expulsion and occlusion. Variation in these trace elements within the coral skeleton can be used as potential tracers of short-lived bleaching events.

Regional hard coral distribution within geomorphic and reef flat ecological zones determined by satellite imagery of the Xisha Islands,South China Sea

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 flat 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 km^2, and the emergent reefs covered ~787 km^2. Hard corals of emergent reefs were considered to cover 97 km^2. 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.

Characteristics and distribution patterns of reef complexes on the carbonate platform margin in deep water areas:the western South China Sea

As a potential oil and gas reservoir, reef complexes have been a research focus from petroleum geologists for a long time. There are favorable conditions for the development of reef complexes in the South China Sea; however, their internal structures, evolution and distribution are still poorly understood. Based on 2D and 3D seismic data, the internal structures and evolution patterns of the reef complexes on the carbonate platform margin in the deep water areas over the western South China Sea were studied in detail. The result shows that two types of reef complexes, i.e., fault controlling platform margin reef complexes and ramp reef complexes have been developed in the study area. The reef complexes have independent or continuous mound or lenticular seismic reflections, with three internal structures （i.e., aggrading, prograding and retrograding structures）. There are different growth rates during the evolution of the reef complexes, resulting in the formation of catch-up reefs, keep-up reefs and quick step reefs. The study also reveals that different platform margin reef complexes have different internal structures and distributions, because of the different platform types. These results may be applied to the exploration and prediction of carbonate platform margin reef complexes in other areas that are similar to the study area.

Geochemical Characteristics of the Trace and Rare Earth Elements in Reef Carbonates from the Xisha Islands(South China Sea): Implications for Sediment Provenance and Paleoenvironment

Based on the concentrations of the trace elements,rare earth elements(REE),and Sr isotopic compositions in reef carbonates from the well‘Xike-1’reef core of the Xisha Islands,the constraints on sediment provenance and paleoenvironment were defined.Variations of the terrigenous input into the paleoseawater were traced in detail and the paleoenvironment and sediment provenance were further investigated.The results show that the HREE/LREE values in the reef carbonates are negatively associated with their Th and Al concentrations;however,their Al and Th concentrations show positive correlation.The lowest 87 Sr/86 Sr values in the reef carbonates generally coincide with the lowest values of Al,Th concentrations and the highest values of HREE/LREE.These data indicate that the HREE/LREE,Al concentrations,and Th concentrations of the reef carbonates are useful indexes for evaluating the influence of the terrigenous inputs on the seawater composition in the study area.From top to bottom,the changing process of the HREE/LREE values and Al,Th concentrations can be divided into 6 intervals;they are H1(0–89.30 m,about 0–0.11 Myr),L1(89.30–198.30 m,about 0.11–2.2 Myr),H2(198.30–374.95 m,about 2.2–5.3 Myr),D(374.95–758.40 m,about 5.3–13.6 Myr),L2(758.40–976.86 m,about 13.6–15.5 Myr),and H3(976.86–1200.00 m,about 15.5–21.5 Myr).Moreover,the changing trend of the HREE/LREE values coincides with that of the seawater δ^13C values recorded by benthonic foraminiferal skeletons from the drill core of ODP site 1148 in the South China Sea(SCS),but not with that of the seawaterδ18O values.The high uplifting rates of the Qinghai-Tibet Plateau coincide with the high Th and Al concentrations and the low HREE/LREE values in the reef carbonates.These data indicate that the main factors controlling the changes of terrigenous flux in the SCS are the tectonic activities associated with Qinghai-Tibet Plateau uplifting and the variations of uplifting rates rather than paleoclimatic changes.

Remote sensing expert system of South China Sea coral reefs

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.

Composition and Distribution of Planktonic Ciliates in the Southern South China Sea During Late Summer： Comparison Between Surface and 75 m Deep Layer

Ciliates are very important components in most marine ecosystem.They are trophic link between the microbial food web and grazing food chain.In this study,ciliates were collected from 11 sites in the southern South China Sea(SCS) during August 25 to September 28,2011.Their composition and distribution at the surface and 75 m deep depth of the ocean were studied.A total of 30 species belonging to 22 genera were identified,and 22 species of 15 genera were Tintinnids.Eutintinnus fraknoii and E.stramentus were the most common species.The other dominants were strombidiids ciliates including Strombidium conicum and S.globosaneum,which were followed by the tide form,Mesodinium pulex.Ciliates abundance ranged from 46 ind L^(-1) to 368 ind L^(-1) in the open sites,46–368 ind L^(-1) at surface and 73–198 ind L^(-1) at 75 m deep layer.In the Yongshu reef,ciliates abundance ranged from 167 ind L^(-1) to 365 ind L^(-1) in the water column,similar to that in Sanya coral reef waters.Ciliates composition showed obvious difference between surface and 75 m deep layer at station S2(P < 0.05),while no similar result was observed at other sites.At 75 m deep layer,salinity was negatively related to mixed layer depth(P < 0.05),but positively to chlorophyll a concentration(P < 0.05),indicating that the change of vertical mixing in water column influenced vertical distribution of ciliates in the southern SCS.

南海长棘海星物种有效性探讨

南海长棘海星暴发已严重威胁到该海域珊瑚礁生态系统健康,乃至整个南海生物多样性。针对南海长棘海星拉丁学名混用、中文名不统一的现状,我们采集了中沙群岛济猛暗沙海域长棘海星样品,结合长棘海星此前物种分类和分布的研究结果,对南海长棘海星物种有效性进行探讨。结果表明:所有长棘海星序列明显分为4个类群,各类群间遗传距离范围为0.087 5~0.104 7,达到了种间差异水平。南海长棘海星与长棘海星的太平洋种聚类到一起,实为太阳长棘海星(Acanthaster solaris),与其余3个种存在明显的种间差异。太阳长棘海星中2个支系间的遗传距离为0.005 3,在COⅠ基因层面属于种内差异。南海长棘海星物种有效性的研究结果为后续开展其遗传特征与适应性机制、种群分布与扩散机制、种群暴发机制等内容的研究提供科学依据。

Seismic Image Prediction of Cenozoic Reef-Banks in the Northwestern South China Sea

The Cenozoic reef-banks reservoir in Qiongdongnan （琼东南） basin is one of the most profitable targets worthy of prospecting in the deep water area of the northwestern South China Sea. In this study, the characteristics of organic reef-like reflectors in southern uplift area of Qiongdongnan basin are analyzed based on the latest 2D and 3D seismic data. It is found that reef-like reflectors in Qiongdongnan basin show high-amplitude moundy continuous reflection at the top and the bottom, chaotic reflection inside the reef-like reflector and there is obviously speed difference between reef-like reflector body and surrounding rock. Combining the geological setting of reef and comparative analysis, the reef-like reflectors are considered to be the reef-banks. Furthermore, the results show that there are three kinds of reef structures in the southern uplift area of Qiongdongnan basin： the fault controlling structure, the fault flexure structure and the carbonate ramp structure. Each structure has its own grow-units that can reveal the growth process of the reef in order. The distribution of reef-like reflec- tors in space shows an arc belt pattern. According to this, four reef arc belts are identified, and their spatial trends are thought to have a good relationship with the buried fault. The internal structure con- stitution and the growth state of reef-like reflectors are mainly controlled by the geomorphology and monsoon-ocean current. The result has an instructive significance to oil-gas exploration of organic reef not only in Qiongdongnan basin, but also even in deep water areas of the South China Sea.

Astronomical tuning and magnetostratigraphy of Neogene biogenic reefs in Xisha Islands, South China Sea

Biogenic reefs are one of two major depositional types in the South China Sea, and are constructed by coral, algae and bryozoa. The West Pacific is a major area of biogenic reef development and plays a critical role in the global carbon cycle. However, the lack of geochronological studies in previous works inhibits our understanding of their contributions. Herein, we conduct a cyclostratigraphic and magnetostratigraphic study on Neogene biogenic reefs using the XK–1 core that was drilled at the Shidao Island,Xisha(Paracel) Islands. The main findings of this study are:(1) the establishment of reliable magentostratigraphy for Ledong, Huangliu, Meishan and Sanya Formations;(2) the magnetic susceptibility variation can be inferred as growth index and tuned to the 405–ka long eccentricity cycle;(3) the astronomical geochronology suggests that the bottom ages for Ledong, Yinggehai, Huangliu, Meishan,and Sanya Formations are 2.2 Ma, 5.7 Ma, 10.4 Ma, 16.6 Ma, and 24.3 Ma, respectively; and (4) Earth's eccentricity and obliquity played predominant roles in biogenic reef establishment on orbital to tectonic timescales. Thus, the reported geochronology offers an opportunity to test the contributions of various factors and hypothesize their roles in the global carbon cycle in future.

Coral reefs in the South China Sea:Their response to and records on past environmental changes

This paper reviews both the recent and longer-term(Holocene) ecological history of coral reefs in the South China Sea(SCS).(1) Local ecological monitoring since the 1960s shows that the coral reefs in the South China Sea have declined dramatically,reflecting the rapid decrease of living coral cover and the great loss of symbiotic zooxanthellae.Collectively,this has led to a significant decrease of annual CaCO3 production.Heavy anthropogenic activities and global warming are recognized as major triggers of the observed coral reef degradation.Observations show that the modern coral reefs in the SCS are a source of at-mospheric CO2 in summer.(2) Coral reefs of the SCS have been widely used to reveal longer-term environmental variations,including Holocene high-resolution sea surface temperature(SST) and abrupt climate events,millennial-scale El Nio varia-tions,millennial-and centennial-scale sea level oscillations,strong and cyclic storm activities,East Asian monsoon intensities,variation in seawater pH,and recent seawater pollution.(3) Coral reefs of the southern SCS have experienced repeated epi-sodes of bleaching over the last 200 years due to high SST and intense El Ni o events;coral reefs of the northern SCS suffered high levels of mortality during several abrupt winter cold-water bleaching events during the middle Holocene warm period.On average,recovery after the middle Holocene cold-bleaching took 20-30 years;recovery following other middle Holocene en-vironmental stresses took approximately 10-20 years.Such findings have significantly contributed to the understanding of the present ecological pressures faced by the coral reefs in the SCS,the histories of Holocene climate/environment changes,and the long-term models of coral reef responses to various past environmental changes.

Modern microbialites and their environmental signifi-cance,Meiji reef atoll,Nansha (Spratly) Islands,South China Sea

Meiji (Mischief) coral atoll, in Nansha (Spratly) Islands, South China Sea, consists of an annular reef rim surrounding a central lagoon. On the atoll rim there are either protuberant 'motu' (small coral patch reefs on the rim of atoll) islets or lower sandy cays that contain modern microbialite deposits on the corals in pinnacles and surrounding bottoms of the atoll. Microbialites, including villiform, hairy, and thin spine growth forms, as well as gelatinous masses, mats and encrustation, developed on coral colonies and atoll rim sediments between 0 and 15 m deep-water settings. The microbialites were produced by natural populations of filamentous cyanobacteria and grew on (1) bulbous corals together with Acropora sp., (2) on massive colonies of Galaxea fascicularis, (3) on dead Montipora digitata, and (4) on dead Acropora teres, some hairy microbialite growing around broken coral branches. This study demonstrates that microbial carbonates are developed in coral reefs of South China Sea and indicates that microbial processes may be important in the construction of modern reef systems. The results have significance in the determination of nature and composition in microorganisms implied in the formation ancient microbialites, and permit evaluation of the importance of microbial deposits in mo-dern coral reefs and of 'microbialites' in biogeochemical cycles of modern coral reef systems. The re-sults also provide evidence of modern analogues for ancient microbialites in shallow-water settings, and combine with sedimentological studies of ancient microbialites to understand their controls.

Seismic interpretation and hydrocarbon accumulations implication of the Miocene Meishan Formation reefs in southern Qiongdongnan Basin, northern South China Sea

Numerous moundy reflections were found at the Upper Meishan Formation in southern Qiongdongnan Basin, South China Sea which are suspected reefs. However, no common understanding on the seismic and geologic interpretation was acquired. Based on seismic reflection identification, geometrical configuration description, wave impedance inversion, forward simulation, analysis of reef-building sedimentary environments and pseudomorph identification, these suspected-reef moundy reflections were studied in details.Three types of reefs were recognized, i.e., patch reef, platform-edge reef, and pinnacle reef. They have some typical characteristics of reefs, including moundy or lenticular shape, clear outline with crest and canal, internal foreset bedding, bidirectional uplap between limbs, and strong reflection at top and bottom. The patch reefs are of moundy seismic facies, with moderateestrong amplitude and moderate frequency, and distribute at the higher part of southern slope belt. Fore-reef and back-reef of patch reefs are slightly asymmetrical being perpendicular to palaeo-bathymetric orientation; while symmetrical to slightly asymmetrical being parallel to the palaeo-bathymetric orientation, and the wave impedance value is about 7 kg/m^3×m/s.Platform-edge reefs are of flat-moundy seismic facies with strong amplitude and moderate frequency, which develop at the carbonate platform edge of higher part of southern slope belt, and the wave impedance value is about 7.5 kg/m^3×m/s. Pinnacle reefs grow up on volcanic cones, forming the complex of pinnacle reef and volcanic cone. The Miocene Meishan Formation reefs in southern Qiongdongnan Basin, northern South China Sea, with high quality sourceereservoireseal assemblages, have good petroleum exploration prospects.

Coral reef ecosystems in the South China Sea as a source of atmospheric CO_2 in summer

由空至海的 CO2 的领域大小在华南海的三个珊瑚礁石区域交换(即 Nansha 岛的 Yongshu 礁石环礁，南部的华南海(SCS ) ；Xisha 岛的 Yongxing 岛，北方中央的 SCS；并且在海南岛的 Sanya 的 Luhuitou Fringing 礁石，北 SCS ) 在 2008 和 2009 的夏天期间揭示了那 CO2 (pCO2 ) 的部分压力显示出的空气和表面海水常规日报周期。最小的价值在早上发生在晚上和最大的价值。在每三个学习区域的空气 pCO2 出现了小日报变化，当时大日报变化在海水 pCO2 被观察。日报海水 pCO2 的变化振幅是 70 摩尔摩尔? 1 在 Yongshu 礁石泻湖， 420619 摩尔摩尔? 1 在 Yongxing 岛礁石公寓，和 264579 摩尔摩尔上? 1 在 Luhuitou Fringing 礁石的礁石公寓上，并且 324492 摩尔摩尔? 1 在就在这 fringing 礁石外面的一个邻近的区域。关于空间关系，在越过华南海的由空至海的 CO2 流动有大差别(例如 0.4 mmol CO2 m ? 2 d ? 1 在 Yongshu 礁石， 4.7 mmol CO2 m ? 2 d ? 1 在 Yongxing 岛，并且 9.8 mmol CO2 m ? 2 d ? 1 在 Luhuitou Fringing 礁石)。然而，这些积极的值建议 SCS 的珊瑚礁石生态系统可以是到空气的 CO2 的网络来源。另外的分析显示了那日报在浅水礁石公寓的表面海水 pCO2 的变化主要被生物新陈代谢的过程控制，当那些被两个生物新陈代谢和水动力学因素更深的水泻湖和外部礁石区域调整时。不同于开的海洋，无机的新陈代谢在在珊瑚礁石生态系统影响海水 pCO2 变化起一个重要作用。

Crustal activities recorded incoral reefs in the northwestern South China Sea

Coral reefs in the northwest of South China Sea have recorded the information from not only the environmental variation but also the crustal activities there during their development. The main crustal activities correlated with the coral reef development include fault, seismic, and volcano activities, etc. The high-resolution spark seismic profiles in the northwestern South China Sea show that the fault activities in the coral reef region have been clearly recorded, and appear as neonatal faults incising reefs. Earthquakes in the coral reef region are rather intense, especially the two occurring on December, 31, 1994, and January, 10, 1995, around the southwest of Leizhou Peninsula, with the magnitude of 6.1 and 6.2, respectively. They have great influence on the growth of the local coral reefs. Quaternary volcanos are active in the northwestern South China Sea, especially around the southwest of Leizhou Peninsula, and they have obvious control of the coral reef development. Some submarine volcanoes form the substrates of coral reef, while a few emerge above the sea surface and form coral islands.

南海近岸珊瑚礁海域表层水体中微塑料的分布特征

海洋环境中的微塑料作为近年来备受国内外关注的一种新型污染物,具有颗粒小、难去除和分布广等特性,并且易携带有毒有害物质,易被生物吸收,因此海洋微塑料成为影响珊瑚礁生态系统健康的重要因素.研究近岸珊瑚礁海域水体中微塑料的污染分布特征有助于了解陆源污染对近岸珊瑚礁生态系统的影响,为珊瑚礁海域生态环境保护提供基础数据.为探究中国南海近岸珊瑚礁海域(文昌和徐闻海域)表层水体中微塑料的分布特征,本研究采用拖网法(0.33 mm)在该海域设置10个站位并收集表层水体中的微塑料样品,经过微塑料鉴定及数据统计分析后,得出以下结论:(1)南海近岸珊瑚礁海域表层水体微塑料的平均丰度为(1.186±1.370)n·m^(-3),高于外海珊瑚礁海域;与国内外其他近岸海域相比,其丰度处于中等水平.(2)粒径0.1—3.0 mm范围内的微塑料数量检出最多,占总数的82.1%;文昌珊瑚礁海域微塑料的主要成分是聚对苯二甲酸乙二醇酯,主要颜色为白色,形状以纤维为主;徐闻珊瑚礁海域主要成分为聚丙烯、聚乙烯、聚苯乙烯,主要颜色为白色和透明,形状分布相对均匀,以片状和泡沫状为主.(3)南海近岸珊瑚礁海域表层水体中微塑料的分布主要受地形、河流输入和人类活动的影响,丰度高值站位主要位于海湾、港口、河口等易于微塑料的积累的位置.(4)生产和生活污水排放是文昌珊瑚礁海域表层水体中微塑料的主要来源,而废弃的日用品和农渔业用品是徐闻珊瑚礁海域表层水体中的微塑料的主要来源.人类活动对海洋微塑料丰度和组成有很大影响,因此,应加强南海近岸珊瑚礁海域的污水排放和渔业活动管控,预防和减少微塑料污染.

南海热带岛礁生物土壤结皮中细菌的分离及其固砂特性初步研究

南海热带岛礁生物土壤结皮中有大量可分泌胞外多糖的微生物,这一特性对固砂具有重要的促进作用。本研究利用TSA、改良TSA、MA三种培养基对采自南海永暑礁及三亚鹿回头海岸带的生物土壤结皮进行可培养细菌的分离纯化。本研究共分离纯化70株细菌,并进行基于16S rRNA基因序列的鉴定,发现所分离的菌株属于3门5纲12目19科25属,厚壁菌门(Firmicutes)为优势门,芽孢杆菌属(Bacillus)为优势属。此外,有22株菌与已知物种16S rRNA基因相似性低于98.65%,为潜在的新物种。纯化菌株的胞外多糖采用乙醇沉淀法提取、苯酚硫酸法检测含量,发现19株菌胞外多糖含量高于0.013mg·mL-1。选取其中胞外多糖含量最高的9株菌进行土壤团聚能力的测定,发现将菌株SCSIO 17111(Lysobacter sp.)菌液喷洒于珊瑚砂表面能够使土壤团聚体保持稳定。针对粒径小于0.2mm的细砂,菌株SCSIO17111固结的砂土在经过干筛处理后,保留量可达92.7%。本研究可为岛礁珊瑚砂的固定、减少土壤流失提供高产胞外多糖菌株资源,还可以为促进岛礁生物土壤结皮的形成提供新的研究思路和方法。

基于SWOT分析的南海区海洋牧场发展路径

海洋牧场作为修复海洋生态系统和实现渔业资源增殖的现代渔业模式,是促进海洋经济绿色发展、推动传统渔业转型升级和构筑海洋命运共同体中的重要一环。然而,在实际建设中存在多种制约现代海洋牧场高质量发展的因素。合理规划海洋牧场,充分发挥其生态、社会、经济效益,对海洋牧场持续发展至关重要。文章对南海区海洋牧场的建设、技术发展及政策管理现状进行了总结,并利用SWOT分析法对南海区海洋牧场的发展情况进行了综合分析,阐释了南海区海洋牧场发展存在的优势、劣势、机遇和挑战,并结合国内外海洋牧场建设的经验及发展趋势,提出了南海区海洋牧场产业发展的路径,以期为我国海洋牧场高质量发展提供借鉴。

浮鱼礁发展现状及其在南海海洋牧场中的应用展望

发展现代化热带海洋牧场是养护南海渔业资源、保护海洋生态环境等方面的重要手段,对中国南海渔业资源养护与科学利用具有深远意义。人工鱼礁是海洋牧场生境营造的重要手段之一,由于南海水深较深,常规鱼礁难以发挥作用,而浮鱼礁可以利用中上层的水体空间,是营造深水渔场的最佳设施。本研究综述了浮鱼礁的类型、功能和应用场景,对国内外的相关研究以及现状进行总结,并对浮鱼礁未来在南海海洋牧场信息化监测、休闲渔业、中上层鱼类资源养护和构建大洋性海洋牧场等方面进行了展望。

High-precision U-series dating of Holocene corals from South China Sea by thermal ionization mass spectrometry(TIMS)

Using the isotopic diluting and thermal ionization mass spectrometric (TIMS) technique, the U-series dating procedure was established on the basis of measurement of national standard GBW04412. With this highly precise technique the Holocene corals from the South China Sea were dated. Comparison between this method and α-spectrometry was made. The results show that a thriving period of corals in the South China Sea appeared at 6 800—5 800 a BP, during which the paleosea level was the higher than at present in the Holecene.