南海西沙和南沙捕获器浮游有孔虫通量季节变化与区域对比

对2012—2013年南海西沙和南沙沉积物捕获器中浮游有孔虫进行了分析,共鉴定出13属20种,群落组合以热带亚热带暖水属种为主。上层捕获器中浮游有孔虫年通量在南沙海区(201 480枚·m~(-2)·y~(-1))明显较高,是西沙海区(99 676枚·m~(-2)·y~(-1))的两倍多。在西沙海区,下层捕获器浮游有孔虫年通量(207 386枚·m~(-2)·y~(-1))是上层的两倍多,且小粒径(150～250μm)壳体主要集中在下层,推测是区域的深层水流侧向搬运所导致。浮游有孔虫总通量和主要属种Globigerinoides sacculifer,G.ruber,Neogloboquadrina dutertrei,Globigerinita glutinata,Globigerinella aequilateralis和Pulleniatina obliquiloculata的通量均呈现出明显的季节变化。西沙浮游有孔虫的通量主要出现在冬半年,有两个明显峰值,分别出现在季风间歇期和冬季风盛行期间;南沙浮游有孔虫通量则与季风变化密切相关,表现为冬夏"双峰型",在冬季12月—3月和夏季5月—8月呈现较高通量。南沙夏季的通量峰值主要由Globigerinoides sacculifer贡献。Globigerina bulloides几乎只在冬季出现,而Globigerinoides conglobatus只出现在夏季,研究认为它们分别有作为南海冬季指示种和夏季指示种的潜力。     

南海南部表层海水古温度估算与次表层海水特征变化

南海南部～2 MaBP以来的表层海水古温度估算表明,表层海水温度变化在更新世冰期旋回中波动比南海北部为小、保持比较温暖,但在长时间尺度上转换函数古水温仍然存在一定的变化趋势。转换函数古温度计算的低温时期并不与冰期相对应,表明南海南部具有独特的表层海洋演化特征,可能与次表层水体性质、上部水体结构等密切相关。过去2 MaBP以来的浮游有孔虫组合演化表明,南海南部海水温跃层呈现由氧同位素MIS79期向～53期相对变浅,自MIS 53期向布容／松山(B／M)古地磁界线附近变深,然后,自布容／松山界线以来又相对变浅的演化过程。     

低纬季风区现代浮游有孔虫主要属种的分布特征及其环境指示意义

提要本次工作利用2013年4月-2017年11月在低纬季风海区采集的浮游生物分层拖网样品为材料,共鉴定出活体浮游有孔虫27种,以热带-亚热带暖水种和较少的广适性冷水种为主。南海、西太平洋和东印度洋广泛分布的浮游有孔虫优势属种为Globigerinoides sacculifer,Globigerinoides ruber,Neogloboquadrina dutertrei,Pulleniatina obliquiloculata和Globorotalia menardii。优势属种中,表层种G. sacculifer和G. ruber丰度最高、占据全种60%以上,主要集中分布在0～50 m水层,受温度和生产力影响较大;次表层种N. dutertrei和P. obliquiloculata分别生活在0～100m、50～100 m水层,其分布与盐度和生产力密切相关。浮游有孔虫的分布受季风影响明显,冬、夏季风通过改变海水上层的温度、盐度以及温跃层、营养跃层的深度极大影响了浮游有孔虫在平面和垂向上的分布,同时也造成了浮游有孔虫分布的季节性差异。     

中更新世撞击事件对海洋环境的影响--南海ODP1144站的高分辨率记录

本文对采自南海北部ODP1144站(20°3.18′N,117°25.14′E,水深2 037m)385.8-386.4m层段的28个沉积物样品进行了微玻陨石、浮游有孔虫及其同位素分析,以评估中更新世撞击事件对环境的影响.微玻陨石见于孔深386.12-386.38m,而集中分布在386.22-386.25m厚约3cm的地层中.研究结果表明,中更新世撞击事件对环境的影响很可能只是小幅度和短时间(百年左右)的,尽管引起了南海表层海水温度约2℃的下降及其相应的δ18O的加重、浮游有孔虫冷水种含量的上升和暖水种含量的减少,但没有造成海水稳定同位素重大偏移和全球气候的灾难性影响,也没有引起浮游有孔虫在生物演化上的变化.     

末次冰期以来中国海区浮游有孔虫Pulleniatina obliquiloculata含量变化的地层学意义

西北太平洋尤其是中国海区末次冰期旋回中浮游有孔虫Pulleniatina obliquiloculata含量变化研究是近年来最重要的古海洋学内容之一.作者综合分析了中国及邻近海区具有可靠测年地层的深海沉积物柱状样中P.obliquiloculata含量变化,探讨其含量低值事件(PME)的生物地层学意义.末次冰期以来P.obliquiloculata含量变化在中国海区呈现两种变化模式:一是以东海及南海北部为代表的冰期含量低、间冰期含量高的特点;另一种则是南海南部的冰期含量高、间冰期含量低的现象.高分辨率地层记录显示,在这种冰期/间冰期总体变化趋势基础上,我国东海、南海和黑潮源区等广泛存在晚全新世～4 300-2 800 cal yr BP P.obliquiloculata含量低值,但以南海北部与东海冲绳海槽最为明显;而南海南部P.obliquiloculata含量还在冰消期(～16.5-15 cal kyr BP)有另一特征的低含量阶段.因而,末次冰期旋回中国海区P.obliquiloculata含量变化可以作为区域性地层划分和对比的标志.尽管如此,由于黑潮分支水团的影响,冲绳海槽中部和北部部分海域,在末次冰期与PME期间,P.obliquiloculata虽然含量相对较低,但仍可保持3%-5%以上,而非多数站位PME事件中的特征性零含量.研究表明PME事件主要由次表层海水的温度降低、温跃层变浅、上部水体温度梯度增加等引起,与表层海水无关,但引起这些海洋环境变化的原因尚不清楚.     

孢粉、炭屑揭示的黔西高原MIS3b期间古植被、古气候演变

将孢粉与炭屑结合应用于贵州盘县坪地晚更新世剖面,对比高分辨率的NGRIPδ18O、石笋记录分析,用以揭示黔西高原MIS3b期古植被、古气候演变。结果显示:45.16—44.44 ka BP期间,孢粉缺失,炭屑少,说明此时植被稀少,气候寒冷,可能指示H5事件。44.44—44.04 ka BP期间,以禾本科、百合科为主的草本及喜冷湿的蕨类占优势,乔、灌木稀少。炭屑浓度低,但末期出现峰值,说明气候开始由冷湿向温干过渡。44.04—42.5 ka BP期间,禾本科草类继续增加,成为草原植物的主要成分;乔木种类增加,但含量不高。炭屑浓度高,峰值频繁出现,指示气侯温干。42.5—41.29 ka BP期间,草原萎缩,森林面积扩展。针叶、常绿及落叶阔叶林迅速扩展。炭屑浓度总体偏低稳定,指示该时期气候温凉湿润。总之,MIS3b整体较冷,干湿交替出现。     

北冰洋西部表层沉积物中的浮游有孔虫稳定氧、碳同位素与水团性质的关系

浮游有孔虫Neogloboquadrinapachyderma(sin.)在北冰洋的古海洋学研究中已经得到广泛的应用。然而对该属种的研究主要集中在北冰洋的东部。本文对中国首次及第二次北极科学考察在北冰洋西部所采集的32个表层沉积物中N.pachyderma(sin.)壳体进行了稳定氧、碳同位素分析,并试图找出其与水团性质的关系。对北冰洋西部N.pachyderma(sin.)的研究显示,该属种主要生活在北冰洋西部30—100m水深范围,其壳体的δ18O差异在楚科奇海主要反映水体盐度和温度的差异,而在楚科奇海台、北风脊海域和加拿大海盆则主要反映水体盐度的差异。N.pachyderma(sin.)壳体的δ13C差异主要反映水体营养状况的差异,在楚科奇海中部其壳体δ13C的轻值反映低营养盐利用率,在北风脊东侧的加拿大海盆反映营养盐的再生环境,而在楚科奇海台和北风脊海域其壳体δ13C的重值反映低营养环境。     

北大西洋墨西拿期古海洋学:有孔虫和稳定同位素证据（英文）

墨西拿期(7.2-5.3 Ma)被认为是中新世最重要的时期之一。在上世纪七十年代初,大洋钻探计划(DSDP)对地中海的首次大洋钻探发现整个地中海盆地存在着大量晚墨西拿期的盐类沉积,其上为上新世早期的正常大洋沉积所覆盖,科学家们称之为灾难性的“墨西拿盐度危机”。在接下来的几十年里,科学家们积极尝试寻找地中海盐度危机不容置疑的影响与全球海洋水体历史之间的关系,但收效甚微。在这项研究中,我们对北大西洋的三个DSDP钻孔(552A、608和547A)中169个晚中新世–早上新世岩芯样品中的有孔虫进行了详细研究,包括时常被忽略的小型底栖有孔虫,并对其中82个底栖有孔虫样品和70个浮游有孔虫样品中的特别物种进行了¹⁸O和¹³C分析,以重建北大西洋中新世末期深层环流模式和评估深海环流和墨西拿盐度危机的演变历史。根据δ¹⁸O曲线,我们识别出了墨西拿期有九个气候低谷期(M-9到M-1,按地层顺序),其中M-1和M-5期表明冰川加剧使海平面降低了至少60-73米。在这些事件中,随着冰锋从格陵兰岛向冰岛南部扩展,北大西洋深层水强度明显减弱,甚...     

北部湾海域浮游介形类物种组成、丰度分布及多样性

根据1998年1月～1999年5月北部湾海域4个航次生态环境综合调查资料,对北部湾海域浮游介形类进行分析研究。结果表明,北部湾渔场浮游介形类物种组成较为简单,记录有小型海萤（Cypridina nana）、齿形海萤（Cypridina dentata）、尖尾海萤（Cypridina acuminata）、纳米海萤（Cypridina nami）、针刺真浮萤（Euconchoecia aculeata）、细长真浮萤（Euconchoecia elongata）、后圆真浮萤（Euconchoecia maimai）等18种;隶属于2亚目、2科、4亚科、12属,其中有4种周年出现,9种只在特定的单一季节出现,其余5种季节性出现;夏季和冬季出现的物种数最多,达到11种;春季次之,为9种;秋季最少,只有6种。北部湾浮游介形类可以划分为3个生态类群,即低盐暖水类群、广温广盐类群和高温高盐类群,优势种群主要是近岸低盐暖水类群的针刺真浮萤和尖尾海萤。全海域栖息密度变化范围为0．02～51．58ind．／m^3,年平均1．22ind．／m^3,春季最高,达2．73ind．／m^3,在湾西北部密集有大量的针刺真浮萤;夏季此密集区逐渐向湾中部移动,纳米海萤为其密集种,栖息密度也有所降低;秋、冬季量少,但在湾南、北部各出现一个丰度相对较高的密集区,并由南北向湾中部递减。总生物量具有明显的季节性变化,平面分布趋势与栖息密度相似。生物多样性指数低,以湾口较高、湾顶较低,呈湾口向湾内西北方向递减趋势;全海域年平均多样性阈值为0．329,四季多样性水平皆为Ⅰ级,多样性程度低;多样性程度较高的区域,多出现于受外海水影响较大、水文状况变化较为复杂的海域。对浮游介形类的物种组成、丰度分布及多样性与北部湾的水系、水团、水温及盐度等环境因子的关系进行了探讨。     

Distribution of some planktonic foraminifera species in deep-sea cores from the red sea and their relation to eustatic sea-level changes

Distribution patterns of planktonic foraminifera in four sediment cores from the Red Sea are studied. The most common species are Globigerinoides ruber, G. sacculifer, Globigerinella siphonifera and Orbulina universa. G. ruber and G. sacculifer show opposite trends of distribution in the sediment cores. Abundance of the foraminifera during the glacial periods suggests that the connection of the Red Sea to the Indian ocean was not completely interrupted and the salinity conditions were not extreme.However, higher salinities appear to have existed in the northern Red Sea, where most of the planktonic foraminifera that occur in the southern Red Sea are absent. It is inferred that the salinity in the southern Red Sea during the glacial period was less than 50%, whereas higher salinity might have existed in the north where the influence of the Indian Ocean was minimal.     

浅谈浮游有孔虫群落海水古温度估算

微体化石组合很早就被用来进行海水古温度估算,近年来利用浮游有孔虫组合来估算古温度的方法有IK TF,MAT,RAM,SIMMAX,ANN和ANND等。本文介绍了这六种方法的主要原理和他们适用的纬度和温度范围,并分别利用FP12E、SIMMAX28及ANN等三类方法来估算冲绳海槽255站位、南海17957站位和ODP1143站位的表层海水古温度,比较计算结果的异同,以验证他们的适用性。     

Foraminifera and coccolithophorid assemblage changes in the Panama Basin during the last deglaciation: Response to sea-surface productivity induced by a transient climate change

The responses of community assemblages of planktonic and benthonic foraminifera and coccolithophorids to transient climate change are explored for the uppermost 2 m of cores ODP677B (1.2°N; 83.74°W, 3461 m) and TR163-38 (1.34°S; 81.58°W, 2200 m), for the last ∼ 40 ka. Results suggest that the deglaciation interval was a time of increased productivity and a major reorganization of planktonic trophic webs. The succession in dominance between the planktonic foraminifera species Globorotalia inflata, Globigerina bulloides, and Neogloboquadrina pachyderma denote four periods of oceanographic change: (1) advection (24-20 ka), (2) strong upwelling (20-15 ka), (3) weak upwelling (14-8 ka) and (4) oligotrophy (8 ka to present). Strong upwelling for the deglaciation interval is supported by the low Florisphaera profunda/other coccolithophorids ratio and the high percentage abundance of Gephyrocapsa oceanica. Benthonic foraminifera assemblage changes are different in both cores and suggest significant regional variations in surface productivity and/or oxygen content at the seafloor, and a decoupling between surface productivity and export production to the seafloor. This decoupling is evidenced by the inverse relationship between the percentage abundance of infaunal benthonic foraminifera and the percentage abundance of N. pachyderma. The terrigenous input of the Colombian Pacific rivers, particularly the San Juan River, is suggested as a possible mechanism. Finally, the Globorotalia cultrata/Neogloboquadrina dutertrei ratio is used to reconstruct the past influence of the Costa Rica Dome-Panama Bight and cold tongue upwelling systems in the Panama Basin. A northern influence is suggested for the late Holocene (after 5 ka) and the last glacial (before 20 ka), whereas a southern influence is suggested for the 20-5 ka interval. There is a correspondence between our reconstructed northern and southern influences and previously proposed positions of the Intertropical Convergence Zone (ITCZ) after the Last Glacial Maximum (LGM).     

Environmental and climatic changes in the central Mediterranean Sea (Siculo–Tunisian Strait) during the last 30 ka based on dinoflagellate cyst and planktonic foraminifera assemblages

A high resolution micropalaeontological study of the core MD 04-2797 CQ recovered in the Sicilian–Tunisian Strait provides insights into the paleoclimatic history of the Mediterranean Sea at the transition between the western and eastern basin over the last 30 ka. Using the analysis of dinoflagellate cyst and planktonic foraminiferal assemblages, we reconstruct the paleoenvironmental changes that took place in this region. High abundances of cold temperate dinocyst species (Nematosphaeropsis labyrinthus, Spiniferites elongatus, Bitectatodinium tepikiense) and the polar planktonic foraminifera Neogloboquadrina pachyderma (left coiling) reveal three major cooling events synchronous with North Atlantic Henrich events 1 and 2 (H1 and H2) and the European and North Atlantic Younger Dryas event. During the Holocene, the presence of warm dinocyst species (Spiniferites mirabilis and Impagidinium aculeatum) and planktonic foraminifera (Globorotalia inflata and Globigerinoides ruber), reflects a significant increase of sea surface temperatures in the western Mediterranean basin, but a full warming was not recorded until 1500 years after the onset of the Holocene. Moreover, our results show that the Holocene was interrupted by at least four brief cooling events at ~ 9.2 ka, ~ 8 ka, ~ 7 ka and ~ 2.2 ka cal. BP, which may be correlated to climatic events recorded in Greenland ice cores and in the Atlantic Ocean.     

Fluxes and isotopic composition of planktonic foraminifera off Hainan Island,northern South China Sea: Implications for paleoceanographic studies

Planktonic foraminifera collected from a sediment trap deployed off Hainan in the northwestern South China Sea (SCS-NW) between July 2012 and April 2013 were studied to evaluate their seasonal variability and ecology as well as to infer the factors controlling their shell fluxes. The total planktonic foraminifera flux, as well as the fluxes of the dominant species (Globigerinoides ruber, Globigerinoides sacculifer and Neogloboquadrina dutertrei), showed three distinct maxima during SW-monsoon in August 2012, the SW-NE intermonsoon in October 2012 and the NE-monsoon in December 2012–February 2013. These periods were characterized by upwelling, aerosol fallout, and intense wind mixing, respectively, from which the foraminiferal assemblages benefitted, as indicated by the close correlation between wind speed, sea surface temperature (SST), chlorophyll a concentration (Chl-a), δ¹⁸O of G. ruber and the shell fluxes. The correlation also suggests that temperature and food availability might have been the primary drivers of the observed changes in foraminiferal abundance. The offset between the SST deduced from flux-weighted of G. ruber δ¹⁸O and annual mean SST is only ∼0.3 °C, much lower than ∼5.2 °C between the summer and winter temperature, indicating a balanced seasonality bias in the shell flux. The linear regression between the satellite-derived sea surface temperature and G. ruber δ¹⁸O reveals the strong potential of this species, at least in the studied region, as an ecological indicator for past oceanic environments.     

Geographical distribution of cryptic genetic types in the planktonic foraminifer Globigerinoides ruber

We present SSU rDNA data resolving the seasonal and geographical distribution of 'cryptic' genetic types of the planktonic foraminifer morphospecies Globigerinoides ruber in the eastern Atlantic Ocean and the Mediterranean Sea. Analysis of 262 sequences revealed the presence of five genetic types belonging to two distinct lineages. Although the morphospecies G. ruber occurs throughout the investigated region, its constituent 'cryptic' genetic types show a pattern of widespread exclusion, which is difficult to reconcile with the concept of ubiquitous dispersal. One of the newly discovered genetic types was exclusively found at stations in the Mediterranean Sea, possibly representing the smallest-scale example of endemism known in planktonic foraminifera. In general, our results suggest that the geographical scale of mutual exclusion between the genotypes is negatively correlated with their phylogenetic relatedness: the most similar and most recently diverged pair of siblings showed the strongest evidence for small-scale competitive exclusion. This pattern is consistent with the concept of niche partitioning, implying decreasing level of competition between genetic types with increasing degree of genetic divergence.     

Paleoceanographic conditions in the western Caribbean Sea for the last 560 kyr as inferred from planktonic foraminifera

Faunal analyses of planktonic foraminifera and upper-water temperature reconstructions with the modern analog technique are studied and compared to the magnetic susceptibility and gamma ray logs of ODP Core 999A (western Caribbean) for the past 560 kyr in order to explore changes in paleoceanographic conditions in the western Caribbean Sea. Long-term trends in the percentage abundance of planktonic foraminifera in ODP Core 999A suggest two hydrographic scenarios: before and after 480 ka. High percentage abundances of Neogloboquadrina pachyderma and Globorotalia inflata, low abundances of Globorotalia menardii and Globorotalia truncatulinoides, low diversity, and sea-surface temperatures (SST) under 24 °C are typical characteristics occurring from 480 to 560 ka. These characteristics suggest a “shallow” well-oxygenated upper thermocline and the influx of nutrients by either seasonal upwelling plumes and/or eddy-mediated entrainment. The second scenario occurred after 480 ka, and it is characterized by high and fluctuating percentage abundances of Neogloboquadrina dutertrei, G. truncatulinoides, G. menardii, Globigerinita glutinata, Globigerinella siphonifera, and Globigerinoides ruber; a declining trend in diversity; and large SSTs. These characteristics suggest a steady change from conditions characterized by a “shallow” thermocline and chlorophyll maximum to conditions characterized by a “deep” thermocline (mainly during glacial stages) and by more oligotrophic conditions. The influence of the subtropical North Atlantic on the upper thermocline was apparently larger during glacial stages, thus favoring a deepening of the thermocline, an increase in sea-surface salinity, and a dramatic reduction of nutrients in the Guajira upwelling system. During interglacial stages, the influx of nutrients from the Magdalena River is stronger, thus resulting in a deep chlorophyll maximum and a fresher upper ocean. The eddy entrainment of nutrients is the probable mechanism responsible of transport from the Guajira upwelling and Magdalena River plumes into ODP 999A site.     

Temperature sensitivity of planktic foraminifera and its influence on the oxygen isotope record

We used oxygen isotope measurements from Holocene surface sediments to infer optimum temperature and temperature sensitivity of the planktic foraminiferal species Globigerinoides ruber (pink) and Globigerinoides sacculifer. The (isotopic) optimum temperature of G. ruber (pink) is close to 27°C. G. sacculifer seems to have optimum vital conditions around 22°C and is less temperature sensitive than G. ruber (pink). Our estimations of optimum temperature and temperature sensitivity are in good accordance with laboratory and field investigations. Two simple experiments show that the temperature sensitivity of planktic foraminifera, determined from oxygen isotopes, can influence phase and amplitude of oxygen isotope records, if the temperature distribution at the sea surface changes through time. To use this distortion for paleoceanography, we suggest to derive an ‘isotopic transfer function’ which allows the calculation of average temperature, temperature variability and the isotopic composition of seawater if the oxygen-isotope differences between at least three species are known.     

塔斯曼海南部更新世放射虫的生物地层学

本研究利用保存丰富、完好的放射虫对塔斯曼海更新世层序进行地层学分析。对塔斯曼海南部更新世的KH94-4TSP-4PC岩芯的放射虫组合进行了详细的生物地层学分析,并从8 .6 m长的岩芯中识别出83种放射虫。依据放射虫属种的出现和消失,可得到两个放射虫带,即Chi带(老)和Psi带(新)。Chi带的顶部以Saturnalis cir-culariHaeckel ,Cycladophora pliocenicaHays的最后出现和Triceraspyris antarcticaHaecker的首次出现为标志。Psi带的顶部以Stylatractus universusHay和Antarctissa cylindricaPetrushevskaya的最后出现为标志。这些放射虫带可与浮游生物的有孔虫Globorotalia ( G.) truncatulinoides带进行对比。     

Late pleistocene paleoclimatology: Planktonic foraminiferal analyses of sediment cores from the central North Atlantic

Planktonic foraminiferal analyses of six deep-sea sediment cores from the central North Atlantic east of the Azores Islands between 37°N and 40°N show distinct oscillations in planktonic foramineferal assemblages during the last 300,000 years. A paleoclimatic curve has been constructed using “Total Fauna Analysis” that reveals three glacial and four interglacial episodes. Relatively minor climatic oscillations are superimposed upon the major glacial-interglacial episodes. The paleoclimatic curve is similar to previous paleoclimatic curves from the Atlantic and adjacent areas. Minor paleoclimatic fluctuations are more distinct in paleoclimatic curves from high latitudes of the Atlantic.The faunal assemblages are transitional between subarctic and subtropical assemblages. During portions of the interglacial episodes, the assemblage is dominated by Globorotalia inflata. Neogloboquadrina pachyderma (dextral-coiling) or Globigerina bulloides dominate during the remainder of the interglacial episodes and during the glacial episodes. Glacial episodes are also marked by particularly high frequencies of Globigerina quinqueloba and Globorotalia scitula. Interglacial episodes are also marked by increases in Globorotalia truncatulinoides, Globigerinoides ruber, and Globigerinella aequilateralis.The planktonic foraminiferal faunal oscillations in the cores are complex and cannot be entirely explained by temperature variation. Other parameters such as salinity, nutrients and biological competitin must influence the faunal oscillations.The faunas suggest no major planktonic foraminiferal faunal boundaries migrated across the area between 37°N and 40°N in the central North Atlantic during the last 300,000 years.