Institutional Repository of South China Sea Institute of Oceanology, CAS
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Numerical Simulation for Shallow Strata Stability of Coral Reef in the Southwest of Yongshu Reef (South China Sea)
No full textIn recent years, infrastructure construction on coral reefs has been increasingly developed. Therefore, the shallow strata stability of coral reefs in the South China Sea should be evaluated. This study aims to investigate the profiles for the shallow strata of coral reefs in the southwest of the Yongshu Reef, particularly in the hydrodynamic marine environment, and to establish a geological model for numerical simulation using Geo-Studio. The shallow strata of the coral reefs include mass gravel, sand gravel, mid-coarse sand, silty sand, fine sand, and reef limestone. The shallow reef slope near the lagoon is similar to a 'layer cake', in which the side close to the sea is analogous to a 'block cake'. The simulation results showed that coral reef stability depends on wave loads and earthquake strength and on the physical properties of coral reefs. The factor of safety for the outer reef is greater than 10.0 under static, wave, and seismic conditions; this indicated that the outer reefs were less affected by waves and earthquakes. However, the factor of safety next to the lagoon varied from 0.1 to 5.3. The variation was primarily caused by the thick strata of coral reefs close to the sea (reef limestone, typically with the thickness > 10 m and equivalent to a block). The soil and rock layers in the coral reef strata with thicknesses < 10 m showed weak engineering geological characteristics. Our findings can provide useful information to future construction projects on coral reefs
Hominin occupation of the Chinese Loess Plateau since about 2.1 million years ago
No full textConsiderable attention has been paid to dating the earliest appearance of hominins outside Africa. The earliest skeletal and artefactual evidence for the genus Homo in Asia currently comes from Dmanisi, Georgia, and is dated to approximately 1.77-1.85 million years ago (Ma)(1). Two incisors that may belong to Homo erectus come from Yuanmou, south China, and are dated to 1.7 Ma(2); the next-oldest evidence is an H. erectus cranium from Lantian (Gongwangling)-which has recently been dated to 1.63 Ma(3) and the earliest hominin fossils from the Sangiran dome in Java, which are dated to about 1.5-1.6 Ma(4). Artefacts from Majuangou III5 and Shangshazui(6) in the Nihewan basin, north China, have also been dated to 1.6-1.7 Ma. Here we report an Early Pleistocene and largely continuous artefact sequence from Shangchen, which is a newly discovered Palaeolithic locality of the southern Chinese Loess Plateau, near Gongwangling in Lantian county. The site contains 17 artefact layers that extend from palaeosol S15-dated to approximately 1.26 Ma-to loess L28, which we date to about 2.12 Ma. This discovery implies that hominins left Africa earlier than indicated by the evidence from Dmanisi
Sediment records of long chain alkyl diols in an upwelling area of the coastal northern South China Sea
No full textLong chain alkyl diols in sediment cores were studied in the Yuedong Upwelling (YDU) area in the coastal northern South China Sea to investigate whether sea surface temperature (SST) and upwelling intensity over the last few decades can be traced by the diol-derived indices, i.e., the LDI (long chain diol index) as a proxy for SST and the DI-1 and DI-2 (diol index 1 and 2) as proxies for upwelling intensity. The influence of riverine long chain alkyl diols (e.g., 1,13- and 1,15-diols), which may affect LDI-reconstructed SSTs, was largely ruled out based on the comparison between diol distributions in suspended particulate materials in the Pearl River estuary and the core sediments. LDI-derived SSTs in downcore sediments matched well with local annual mean SSTs. The records of DI-2 changed in parallel with the local wind stress and inversely with SST at times of upwelling, suggesting that DI-2 is an effective proxy for upwelling intensity of YDU. The DI-1 showed a generally inverse variation pattern with DI-2, implying a major influence by SST, and it is thus not an applicable upwelling indicator for YDU. A negative relationship of DI-1 and a positive relationship of DI-2 with LDI-derived SST were observed. This occurrence might be attributed to El Nino-Southern Oscillation (ENSO), because the SST and upwelling intensity were largely modulated by ENSO, showing a warm annual mean SST during the years of enhanced El Nino and intensified summer upwelling. (C) 2018 Elsevier Ltd. All rights reserved
Seismic stratigraphy of the Shatsky Rise sediment cap, northwest Pacific, and implications for pelagic sedimentation atop submarine plateaus
No full textPelagic sediments accumulated atop Shatsky Rise since Early Cretaceous time provide a valuable record of Pacific paleoceanography. The accepted sedimentation model invokes relatively continuous pelagic sediment accumulation punctuated by four regional hiatuses caused by changes in oceanic chemistry. That framework was proposed more than two decades in the past and based on low-quality single channel seismic profiles. It was developed at the center of Tamu Massif, the main topographic high of Shatsky Rise, and extended to other highs with uncertainty owing to sparse data. The availability of high-quality seismic data and additional coring by the Ocean Drilling Program and Integrated Ocean Drilling Program allows a re-examination. Seismic and core data indicate that sedimentation atop Shatsky Rise has been complex, with regional and local variability. Four major hiatuses were previously defined and tentatively correlated to nearby topographic highs. These breaks occurred approximately during the Aptian-Barremian and Cenomanian-Coniacian ages of the Cretaceous and during the Paleocene and Oligocene epochs of the Cenozoic. They are of variable length and tend to be of shorter duration at the summit of Tamu Massif, but of longer durations elsewhere. All produced erosional unconformities that may be related to mass wasting of the sediment cap edges. Each hiatus is approximately correlated with global falls of sea level, suggesting a connection, perhaps to intensified bottom currents at those times. Local variability is observed in the form of discontinuous layering, non-uniform sedimentation, thinning of the sediment caps at their edges, and local erosion near topographic highs. These variations are likely the result of shifting bottom currents, possibly resulting from interactions of internal tides with topography. Shatsky Rise sedimentation is inherently punctuated and non-uniform and the sedimentary record includes significant lateral variability. Other large oceanic plateaus are likely to exhibit similar sedimentary cap complexities
An improved method for integrated ecosystem health assessments based on the structure and function of coastal ecosystems: A case study of the Jiangsu coastal area, China
No full textEcosystem health status assessment is very complex and requires an integrated approach based on combined and synoptic estimates of the environmental background and the study of the structure and function of different ecosystems at a systems level. Here, we present the main results gained over six years (2006-2007, 2009-2012) with the aim of obtaining concise and comprehensive assessment results at 30 routine investigation sites in the Jiangsu coastal area. Our improved approach follows consecutive and interconnected steps. First, we conducted a quantitative assessment of community structure, including species abundance, biomass, and diversity utilizing a multidimensional scaling method. Then, a systemic functional assessment was carried out at the genetic level, including eco-exergy and structural eco-exergy, using a means clustering method, passing through a dimensionless polygonal area to reflect the integrated assessment results. Our results indicate that among the four seasons, the health status was best in autumn, followed by spring and winter, and worst in summer. Among the six assessed years, 2006 had the best health status, whereas 2012 had the worst. The general trend of annual variation in ecosystem health status was in decline. As for the regions, the health status was good or moderate in the southern and northern regions, and worst in the central region. Various human interventions and environmental stresses contributed to the stability and resilience of the ecosystem at different time scales and in different areas; however, these effects were not absolutely negative. This new method has strong applicability for assessing the status of ecosystems composed of several communities, as long as the eco-exergy quality and community structure of the system can be estimated
长链烷基二醇及其指标在南海北部粤东沿海上升流地区的环境指示
No full text本文以南海北部粤东沿海夏季上升流三个短柱状岩心为研究对象,通过二醇化合物分布分析测试和二醇环境参数的定量化重建,初步探讨了过去80年来海水表层温度(SST)、上升流活动和沉积环境演变过程及其交互关系。二醇温度指标(LDI)在粤东沿海地区较好地指示了年均SST,在三个岩心中均显示了整体增加的分布特征和相似的多年尺度变化趋势。此外,LDI-SST和二醇参数2具有非常好的线性关系(R~2=0.85,n=49),其整体分布、多年尺度变化均和ENSO旋回一致,并且大部分高/低值和ENSO暖/冷年、南海夏季风强/弱年具有很好的对应关系,表明了二醇参数2可以作为粤东上升流强度变化(多年/单年尺度)的替代性指标。而1,14-二醇含量和ENSO指标在多年尺度上显示了相似的波动特征,但大部分高/低值和南海夏季风指数、ENSO指标呈反相分布,说明了仅用1,14-二醇含量不可反演粤东上升流。据此,利用二醇参数2初步重建了过去80年来粤东上升流演变信息:上升流强度整体上显示加强的分布趋势,大体上呈约2~5年周期变化。此外,三个岩心中1,15-C_(30)(二醇/二醇+酮醇)比值和二醇参数2在整体上和多年尺度上均呈现相反的分布特征,可能与上升流活动导致的1,15-C_(30)二醇母源再悬浮再氧化有关,而普遍较高的1,15-C_(30)二醇比值(≥0.82)反映的强还原环境则和上升流地区水体中含氧量普遍偏低相关
海绵真菌中一个新的聚酮类化合物
No full text利用硅胶柱色谱、凝胶柱、反向柱色谱和高效液相等手段对海绵来源的真菌Alternaria sp.F49在大米培养基中的代谢产物进行分离纯化,从中分离得到一个新的聚酮类化合物:3R,5R-(-)-talaroflavone(2)和15个已知化合物。Ⅰ及Ⅱ是两个消旋体,通过手性柱分别将它们进行拆分得到1和2、3和4两对对应异构体;通过核磁、质谱和文献比对确定了这些化合物的结构,运用X-单晶衍射及圆二色谱等手段确定了化合物1、2的绝对构型;化合物6、8～10首次从该属真菌(Alternaria)中分离出来;化合物16展示出中等的COX-2酶抑制活性,其IC_(50)为7.3μmol·L~(-1)
造礁石珊瑚共附生固氮微生物的固氮活性
No full text造礁石珊瑚是珊瑚礁生态系统的主要建造者,其共附生微生物参与的生物固氮过程可以缓解寡营养海域的氮素限制,从而维持珊瑚礁生态系统较高的初级生产力。本研究以位于海南三亚鹿回头和西沙南沙洲两地的造礁石珊瑚为对象,采用乙炔还原法测定了不同季节及不同物种的珊瑚共附生固氮微生物的固氮活性;同时测定了海水营养盐含量,分析了珊瑚固氮活性与环境因子之间的关系。结果表明:三亚鹿回头海域的鹿角杯形珊瑚(Pocillopora damicornis)、澄黄滨珊瑚(Porites lutea)和芽枝鹿角珊瑚(Acropora gemmifera)的固氮活性无季节性差异;但相同季节3种珊瑚的固氮活性具有显著的物种间差异,其中鹿角杯形珊瑚的固氮活性最高(P<0.05),夏季为5.925×10~(-11)mol C_2H_4·g~(-1)·h~(-1),冬季为6.471×10~(-11)mol C_2H_4·g~(-1)·h~(-1);西沙寡营养条件下的澄黄滨珊瑚的固氮活性在夏季为5.401×10~(-11)mol C_2H_4·g~(-1)·h~(-1),显著高于同一季节三亚鹿回头的澄黄滨珊瑚的固氮活性(1.971×10~(-11)mol C_2H_4·g~(-1)·h~(-1))(P<0.01)。研究表明,在营养盐浓度较高的背景下,珊瑚的固氮活性受环境因子和季节变化的影响较小。西沙南沙州海水中溶解性营养盐浓度的升高可能会减弱珊瑚共附生固氮微生物的固氮能力
1株红树林来源枝孢属真菌的分离鉴定及纤维素酶性质分析
No full text利用水解圈法从三亚红沙河红树林区分离得到1株纤维素降解真菌SCSIO 43503。分子生物学鉴定表明,该菌ITS序列与菌株Ochrocladosporium frigidarii CZ549(FJ755255)的相似度为96%,β微管蛋白(β-tubulin)序列与Shiraia bambusicola(AB355003)的相似性为86%,钙调蛋白(calmodulin)与Paramyrothecium viridisporum CBS 873.85(KU846278)序列相似性为89%;综合其形态学特征,推测其为枝孢属(Gladaxporism)真菌,命名为Gladaxporism sp.SCSIO 43503(KY224732)。进一步对该菌株分泌的纤维素酶进行分析,结果显示该菌株维素酶活性的最适反应温度为50℃,在45~50℃范围内活性较高;最适pH为5.0,在3.0~7.0范围内具有较高的活性,最适发酵时间为3 d。在最优条件下,酶活力达到最高,为23.46 U。本研究发现了一株纤维素降解真菌,对纤维素酶的生产和利用具有重要价值
Characterization of 18S-ITS1-5.8S rDNA in eleven species in Soleidae: implications for phylogenetic analysis
No full textFor several decades, both concerted evolution and non-concerted evolution of rRNA genes have been discovered in a wide variety of species. To explore the evolutionary patterns and to evaluate the variability at the intra-individual and interspecific levels in Soleidae, a total of 233 complete 18S-ITS1-5.8S rDNA sequences from 11 representative species were generated. The results indicated that six species had little variation, suggesting a concerted evolutionary pattern. However, in the other five species, much variation was observed. Two or three types of 18S and ITS1-5.8S, or even the entire 18S-ITS1-5.8S rDNA sequence, were identified, suggesting a non-concerted evolutionary pattern. According to the pseudogene identification criteria, Type B and C in the five species that underwent non-concerted evolution were postulated as pseudogenes. The phylogenetic analysis based on these rDNA sequences showed that some of the pseudogenes diverged from the corresponding species or even clustered with other species, and the potential causes for this are discussed. Further analyses of the pseudogenes revealed that they could also provide particular evolutionary information, suggesting that pseudogenes should be taken into consideration rather than being discarded arbitrarily. Moreover, the results provided molecular support for the inclusion of Pseudaesopia japonica in the genus Pseudaesopia, and not in Zebrias or other genera