热带西太平洋次表层水和中层水分布特征及其年代变化

热带西太平洋是一个流系和水团分布十分复杂的海域。热带西太平洋是一个在别处形成的几种水团的交汇区。许多起源于中、高纬度海域的次表层和中层水团，由不同流系带入和带出这个海域。热带西太平洋水团分布及其变化，与各种时间尺度的大尺度海洋环流和全球水循环变化密切联系，所在位势密度层次越深，所关联的气候变化时间尺度越长。因此，研究该海域次表层水和中层水的分布、扩散及其变化特征，对大洋环流动力学和气候变化研究有重要意义。本文利用中国ARGO资料中心提供的ARGO延时处理资料和美国NODC提供的WOD01中的高分辨率CTD资料，运用盐度极值法确定水团的核心，通过水团核心位置的分布及变化反映热带西太平洋次表层水和中层水的分布及其起源和归宿问题，试图获得较以往更加准确的NPIW和AAIW以及NPTW和SPTW的向南及向北扩散的特征，以及ITF在不同层次上的水源。对新发现的西太平洋热带水（WPTW）和西太平洋热带中层水（WPTIW）的水团性质、分布特征，成因和起源进行了比较系统的分析。在此基础上，分析上述次表层水和中层水20世纪八九十年代以来的年代变化特征。主要结果如下：（1）SPTW在137°E以西跨越赤道后，仍在很大程度上保持原有盐度，向西北和东北方向发展。SPTW在131°E以东几乎没有越过5°N，但在131°E以西可局部影响到6°N，棉兰老冷涡和哈马黑拉暖涡的涡混合输运在这一局部过程中可能起主要作用。NPTW主要位于10°N－20°N之间，在NEC输送下从东向西一直延伸到菲律宾沿岸，分成向北和向南两个分支，南分支在130°E以西沿棉兰老沿岸向南扩散大约到2°N，部分向西进入苏拉威西海，部分与SPTW相遇后有向东扩散的趋势。（2）AAIW几乎齐头并进地向北扩散到12°N－13°N，在125°E附近向北可以到达13°N左右。NPIW的主体分布在10°N以北、122°E以东，呈东北向西南的扩散趋势，在132°E以西至棉兰老沿岸之间可以到达4°N附近。（3）在已知的NPTW与SPTW之间，发现一个以往从未被报道过的次表层水，称之为WPTW。WPTW存在于3°N－12°N之间，核心盐度低于34.8psu，位势密度约在23.7 －24.7 之间。WPTW源于东太平洋20-25°N附近，由NEC南翼携带向西到达西边界后，部分经MC向南，经NECC向东折回，被局限在NEC与NECC之间的狭长水域。（4）2°N－10°N之间、从170°W到西边界分布着一片盐度比较均匀、呈现垂向盐度极小值特征的中层水。该水体位势密度约为26.0 －26.6 、位于AAIW之上、NPIW以南，核心盐度与AAIW相仿、但高于NPIW，在以往研究中未给予重视。从流场配置来看，这个被本文称为WPTIW的水体恰好处在NEC-NECC-SEC之间的强剪切区，在其北侧的是NPIW与同样起源于东北太平洋的浅的盐度极小值（SSM）之间的混合水，在其南侧相应层次上则是AAIW与SPTW之间的过渡水，两者之间被剪切流充分混合，形成盐度相对均匀的WPTIW。因此，WPTIW是热带西太平洋局地混合和再循环的产物。（5）在20世纪八九十年代和2000年以后这两个时期，本文所关注的次表层水和中层水在热带西太平洋扩散和在西边界附近交织在一起的总体态势基本一致。两个时期相比较，SPTW向西扩散程度变化不大，向北扩散程度有所加大，由前一时期的5°N，进一步扩散到6°N－7°N。NPTW在西边界附近的向南扩散程度有所削弱，在2002－2005年间只向南扩散到4°N，并且被SPTW阻挡于128°E以西，而前一个时期则可向南扩散到2°N，并且在2°N－4°N之间转向东跨过130°E。AAIW在西边界附近向北扩散程度有所加大，在2002－2005年到13°N附近，而前一个时期只到达11°N。NPIW在西边界附近的向南扩散程度有所削弱。（6）ITF的次表层水源基本上可以确定主要来自北太平洋，中层水源既有北太平洋，也有南太平洋。其中北太平洋次表层水和中层水经苏拉威西海、望加锡海峡到达弗罗勒斯海，层次越深趋势越明显。南太平洋次表层水没有进入印度尼西亚海域，AAIW则明显是经哈马黑拉海峡和马鲁古海峡到班达海。在各层次上，南海次表层水和中层水通过苏禄海进入ITF的可能性不大。

热带西太平洋环流动力结构分析与模拟

热带西太平洋环流是副热带环流与热带环流关键分量，毗邻西太平洋暖池，对暖池的形成与变化有重要的作用。然而，目前为止，热带西太平洋环流还有许多问题，包括动力结构还不清楚。因此，论文针对热带西太平洋环流的研究不仅在太平洋环流动力学上有理论意义，而且对气候变化的研究和预测也具有理论和实用价值。 太平洋北赤道流分叉是大洋，特别是太平洋西部边界流海域的一个非常突出的环流现象，它是大洋中副热带大流环和热带流环的发源地，很大程度上决定着海盆尺度的大洋环流结构，在大洋环流动力学上具有非常重要的意义和地位；同时它决定着大洋西边界区质量、热量的经向输送，进而对气候变化产生重要影响，是气候系统中不可忽视的重要分量。因此，北赤道流分叉的研究，不仅具有在海洋动力学上科学意义，而且对气候变化和预测也有实践意义。 从30年代至今，关于北赤道流分叉的研究有两种，一是根据实际观测水文数据，二是由数值模拟结果得出结论。用观测数据做出的结果，相对比较接近实际，但资料的分辨率较差，会引起估算结果的偏差；数值模拟结果有较高的时空分辨率，但由于模式本身的某些缺点会导致结果偏离实际。目前为止，诸多有关北赤道流分叉的结果，如分叉纬度变化的结论很不一致。所以，如何找到一种高时空分辨率的数据或提出一个比较符合物理实际并得到实测数据验证的数值模式是研究北赤道流分叉的关键。 本文用1992年10月到2004年12月高时空分辨率的卫星高度计数据，通过计算迹线的方法，确定了北赤道流分叉的纬度。结果表明，年平均分叉纬度约在13.4°N. 关于北赤道流分叉的季节变化，6月份发生在最南端（12.9°N），12月份发生在最北端（14.1°N）。12年的平均结果显示，7月份的分叉纬度比6月份和8月份明显偏大，这是局地风应力旋度导致的结果。本文同时研究了北赤道流分叉的年际变化，结果表明在厄尔尼诺年，北赤道流分叉纬度北移，在拉尼娜年，分叉纬度南移。 在热带西太平洋地区，特别是西边界流区和印度尼西亚贯通流邻近海域，岛屿众多，地形非常复杂，历史水文数据和测流数据又极少，所以几乎无法用分析观测数据的方法求得这一海域海洋环流，特别是次表层环流结构的深刻了解。因此，本文利用一个既适用于开阔大洋又适宜于地形变化剧烈海域的混合坐标海洋模式HYCOM，模拟了热带西太平洋环流，特别是西边界流及其相关海流，如，新几内亚沿岸潜流、棉兰老潜流、赤道潜流和印度尼西亚贯通流的气候态及其月、季变化。模式结果再现了该海域主要流系及其季节变化，模拟得到的海面高度场与卫星高度计数据基本一致；模拟所得的诸多关键断面上的海流、温度和盐度结构与实地观测数据（Johnson et al., 2002）有良好的一致性，说明本文的HYCOM模拟结果是比较可信、可靠的，可以用来做西太平洋环流分析用。本文得到结果如下： （1）赤道潜流究竟起源于何处，是赤道环流动力学上一个重要问题。鉴于实测数据缺乏和赤道潜流起源邻近海域地形复杂，相关研究很少，仅有的几项研究结果认为赤道潜流起源于135－137°E。本文一系列经向跨赤道断面的纬向流速模拟结果表明，赤道潜流最西源于129－130°E之间；另外，事实上，从200米层水平环流的模拟结果来看，赤道潜流有4个源头，各季有所不同：(i) 新几内亚沿岸潜流在135°E附近汇入赤道潜流；与Tsuchiya et al.（1989）结论相同；(ii) 来自棉兰老海流，这与Lu and McCreary（1995），Gu and Philander（1997）结论相同；(iii) 南海水经民都洛海峡、苏禄海和苏拉威西海西部由哈马黑拉岛以北进入赤道潜流，特别是，在春、夏、秋季；(iv) 印度洋海水经班达海和马鲁古海沿苏拉威西东岸北上沿哈马黑拉岛以东汇入赤道潜流（特别是春季）。所以，赤道潜流就水源来说，它有来自南海、印度洋和棉兰老以东的海水，就其起源来说，还是应该算从129－130°E开始的。 （2）棉兰老潜流发现于80年代末，尽管棉兰老潜流的起源对这一海域环流动力学非常重要，但由于资料缺乏，其起源的研究甚少。本文的模拟结果表明棉兰老潜流似乎有一部分水来自棉兰老海流，这主要在300－500米层。但更重要的是，从马鲁古海西边界（苏拉威西岛以东）向北的一支流更是棉兰老潜流的重要水源，说明棉兰老潜流的水源有相当部分是来自南半球，在600，700米层，特别是800，900和1000米层，棉兰老海流流速急剧减小至几乎看不到，而棉兰老潜流非常突出，其水源主要来自南半球苏拉威西岛东部向北的流动。至于棉兰老潜流的去处，500，600米层的模拟结果显示，棉兰老潜流在12－13°N附近，一大部分向东流去，一小部分向南加入棉兰老海流。在700米层以下，棉兰老潜流则在12°N向东流去，这与Hu and Cui（1989, 1991）和Wang and Hu（1998）的结果一致。 （3）关于印度尼西亚贯通流。HYCOM模拟的印度尼西亚贯通流年平均状况指出：250米以浅，印度尼西亚贯通流由西太平洋主要经由望加锡海峡进入东印度洋；300米以深，印度尼西亚贯通流反向，由东印度洋经由弗罗勒斯海、班达海和马鲁古海的西部边界进入太平洋。由200米层环流可以看出，从民都洛海峡南下的南海水是进入望加锡海峡构成印度尼西亚贯通流的主要的来源，另一小部分来自棉兰老海流。 （4）关于黑潮南海分支。在本文的模拟结果中，一年四季都有明显的黑潮分支由吕宋北端向西北进入南海后，沿大约21°N附近向西南流动，宽约100－200公里，深达300－400米，最大流速一般可达20厘米/秒，最大在冬季，可达40厘米/秒，流量约为6.5Sv，冬季强，5、9月份偏弱。证明了仇德忠、杨天鸿、郭忠信（1984）和郭忠信、杨天鸿、仇德忠（1985）关于南海黑潮分支存在的论述，并在一定程度上定量的解释了其季节变化规律。

东、西太平洋深海沉积物细菌多样性研究

深海生物圈有着不同于陆地和浅海的典型特点，例如高压、低温、永久黑暗及寡营养，并且深海微生物具有特殊的代谢途径及庞大的生物量，这使得深海成为一个巨大的有待开发利用的生物资源宝库。 本文研究的样品分别取自东太平洋E272站位(12°36’39"N, 104°19’28"W)和西太平洋Ph05-5站位(16°04’93"N, 124º34’48"E)。E272站位距离东太平洋13°N海隆45km，水深3 191m；而Ph05-5站位地处西菲律宾海盆，在黑潮源区附近，位于西太平洋暖池区边缘，水深3 382m，并且Ph05-5岩芯一共包含了五个明显的火山灰层。 本文采用了末端限制性片段长度多态性分析（T-RFLP）和16S rRNA 基因文库分析的方法在小尺度上对东太平洋E272站位的沉积物样品进行细菌群落结构的研究。研究结果表明沉积物细菌群落结构在小尺度上存在明显的垂直变化。系统进化分析表明，该沉积物样品的细菌多样性较高，共包含9个主要的门类，包括变形菌门、绿弯菌门（绿色非硫细菌）、浮霉菌门、酸杆菌门、放线菌门（高G+C革兰氏阳性菌）、拟杆菌门、硝化螺旋菌门、以及两个待定的门类OP8和TM6。其中变形菌门细菌是一类在海洋中非常常见的细菌，广泛分布于各个海洋环境，在我们的文库当中发现了变形菌门的三个纲，包括α-、-、-变形菌纲。本项研究充分表明该沉积物环境中具有较高的细菌多样性，在小尺度上细菌群落垂直分布明显，其结果也可从侧面反映深海沉积物近表层处的环境条件在小尺度上的垂直变化显著。 对西太平洋暖池区沉积物样品的细菌群落的研究也采用16S rRNA 基因文库分析的方法。系统进化分析表明该沉积物样品细菌的多样性相对较低，一共包含了六个不同的门类，包括变形菌门、浮霉菌门、放线菌门、厚壁菌门（低G+C革兰氏阳性菌）、绿弯菌门、酸杆菌门。在这个沉积物样品中也发现了变形菌门的三个纲包括α-、-和-变形菌纲。聚类分析和系统进化分析都表明表层的细菌群落同其它8层的细菌群落存在明显的差异，并且其它8层包括5个火山灰层和3个远洋粘土层的细菌群落结构差异不大，推测火山灰成分不仅对火山灰层的细菌群落产生影响，而且可能通过扩散对整个沉积物的微生物群落结构都产生影响。表层可能由于沉积时间较晚所以受影响相对较小或表层本身不同于较深层次的理化条件而使表层群落存在较大差异。 对东、西太平洋不同环境下的两个深海沉积物样品的细菌多样性进行比较，结合其它研究发现变形菌门细菌在不同深海环境中都普遍存在，是深海不同环境的广适类群。另外，两个环境中的细菌多样性存在很大差异，东太平洋沉积环境中的细菌多样性要远高于西太平洋沉积环境中的细菌多样性，推测其最可能的原因是西太平洋沉积物火山灰成分对细菌群落的影响，致使其细菌群落与东太平洋远洋粘土沉积物细菌群落产生很大差异；另外，不同洋区的环境差异也应该是造成细菌群落差异的一个重要方面。

14C as a tool to trace terrestrial carbon in a complex lake system: implications for foodweb structure and carbon cycling

Carbon and nitrogen stable isotope analysis (SIA) has identified the terrestrial subsidy of freshwater food-webs but relies on different 13C fractionation in aquatic and terrestrial primary producers. However dissolved inorganic carbon (DIC) is partly comprised of 13C depleted respiration of terrestrial C and ‘old’ C derived from weathering of catchment geology. SIA thus fails to differentiate between the contribution of old and recently fixed terrestrial C. DIC in alkaline lakes is partially derived from weathering of 14C-free carbonaceous bedrock This
yields an artificial age offset leading samples to appear significantly older than their actual age. As such, 14C can be used as a biomarker to identify the proportion of autochthonous C in the food-web. With terrestrial C inputs likely to increase, the origin and utilisation of ‘old’ or ‘recent’ allochthonous C in the food-web can also be determined. Stable isotopes and 14C were measured for biota, particulate organic matter (POM), DIC and dissolved organic carbon (DOC) from Lough Erne, Northern Ireland, a humic but alkaline lake. High winter δ15N values in calanoid zooplankton (δ15N =24‰) relative to phytoplankton and POM (δ15N =6‰ and 12‰ respectively) may reflect several microbial trophic levels between terrestrial C and calanoids. Furthermore winter calanoid 14C ages are consistent with DOC from inflowing rivers (87 and 75 years BP respectively) but not phytoplankton (355 years BP). Summer calanoid δ13N, δ15N and 14C (312 years BP) indicate greater reliance on phytoplankton. There is also temporal and spatial variation in DIC, DOC and POM C isotopes.

Coordinated weather balloon solar radiation measurements during a solar eclipse

Solar eclipses provide a rapidly changing solar radiation environment. These changes can be studied using simple photodiode sensors, if the radiation reaching the sensors is unaffected by cloud.Transporting the sensors aloft using standard meteorological instrument packages modified to carry extra sensors, provides one promising but hitherto unexploited possibility for making solar eclipse radiation measurements. For the 20th March 2015 solar eclipse, a coordinated campaign of balloon-carried solar radiation measurements was undertaken from Reading (51.44N, 0.94W), Lerwick (60.15N, 1.13W) and Reykjavik (64.13N, 21.90W), straddling the path of the eclipse.The balloons reached sufficient altitude at the eclipse time for eclipse-induced variations in solar radiation and solar limb darkening to be measured above cloud. Because the sensor platforms were free to swing, techniques have been evaluated to correct the measurements for their changing orientation. In the swing-averaged technique, the mean value across a set of swings was used to approximate the radiation falling on a horizontal surface; in the swing-maximum technique, the direct beam was estimated by assuming the sensing surface becomes normal to the solar beam direction at a maximum swing. Both approaches, essentially independent,give values that agree with theoretical expectations for the eclipse-induced radiation changes.

Water masses and circulation in the surface layers of the Caribbean at 66ºW

[EN] A meridional hydrographic section was made in August–September 1997 at 66°W from the coast of Venezuela to Woods Hole aboard the R/V Knorr. In this report, we concentrate on near surface measurements in the Caribbean. The data show two distinct water masses with different origins. From approximately 14°N to Puerto Rico, Caribbean Surface Water and Subtropical Under Water with their source in the North Atlantic are found, as previously observed. From Venezuela to approximately 13°N, a less saline water mass with its source in the Tropics and South Atlantic is found. Within the southern portion of the section, two different velocity patterns are observed, namely, an eastward flow with a subsurface maximum near the coast of Venezuela, and a surface intensified westward jet with Velocities of 130 cm s−1 in midbasin.

Synthese und Evaluierung makrozyklischer 68 Ga-MPI-Tracer auf Pyridaben-Basis

Herz-Kreislauf-Erkrankungen zählen weltweit zu den Hauptursachen, die zu frühzeitigem Tod führen. Pathophysiologisch liegt eine Gefäßwandverdickung durch Ablagerung arteriosklerotischer Plaques (Arteriosklerose) vor. Die molekulare Bildgebung mit den nuklearmedizinischen Verfahren SPECT und PET zielt darauf ab, minderperfundierte Myokardareale zu visualisieren, um den Krankheitsverlauf durch frühzeitige Therapie abschwächen zu können. Routinemäßig eingesetzt werden die SPECT-Perfusionstracer [99mTc]Sestamibi und [99mTc]Tetrofosmin. Zum Goldstandard für die Quantifizierung der Myokardperfusion werden allerdings die PET-Tracer [13N]NH3 und [15O]H2O, da eine absolute Bestimmung des Blutflusses in mL/min/g sowohl in der Ruhe als auch bei Belastung möglich ist. 2007 wurde [18F]Flurpiridaz als neuer Myokardtracer vorgestellt, dessen Bindung an den MC I sowohl in Ratten, Hasen, Primaten als auch in ersten klinischen Humanstudien eine selektive Myokardaufnahme zeigte. Um eine Verfügbarkeit des Radionuklids über einen Radionuklidgenerator gewährleisten zu können, sollten makrozyklische 68Ga-Myokard-Perfusionstracer auf Pyridaben-Basis synthetisiert und evaluiert werden. Die neue Tracer-Klasse setzte sich aus dem makrozyklischen Chelator, einem Linker und dem Insektizid Pyridaben als Targeting-Vektor zusammen. Struktur-Affinitätsbeziehungen konnten auf Grund von Variation des Linkers (Länge und Polarität), der Komplexladung (neutral und einfach positiv geladen), des Chelators (DOTA, NODAGA, DO2A) sowie durch einen Multivalenzansatz (Monomer und Dimer) aufgestellt werden. Insgesamt wurden 16 neue Verbindungen synthetisiert. Ihre 68Ga-Markierung wurde hinsichtlich pH-Wert, Temperatur, Vorläufermenge und Reaktionszeit optimiert. Die DOTA/NODAGA-Pyridaben-Derivate ließen sich mit niedrigen Substanzmengen (6 - 25 nmol) in 0,1 M HEPES-Puffer (pH 3,4) bei 95°C innerhalb 15 min mit Ausbeuten > 95 % markieren. Für die DO2A-basierenden Verbindungen bedurfte es einer mikrowellengestützen Markierung (300 W, 1 min, 150°C), um vergleichbare Ausbeuten zu erzielen. Die in vitro-Stabilitätstests aller Verbindungen erfolgten in EtOH, NaCl und humanem Serum. Es konnten keine Instabilitäten innerhalb 80 min bei 37°C festgestellt werden. Unter Verwendung der „shake flask“-Methode wurden die Lipophilien (log D = -1,90 – 1,91) anhand des Verteilungs-quotienten in Octanol/PBS-Puffer ermittelt. Die kalten Referenzsubstanzen wurden mit GaCl3 hergestellt und zur Bestimmung der IC50-Werte (34,1 µM – 1 µM) in vitro auf ihre Affinität zum MC I getestet. In vivo-Evaluierungen erfolgten mit den zwei potentesten Verbindungen [68Ga]VN160.MZ und [68Ga]VN167.MZ durch µ-PET-Aufnahmen (n=3) in gesunden Ratten über 60 min. Um die Organverteilung ermitteln zu können, wurden ex vivo-Biodistributionsstudien (n=3) vorgenommen. Sowohl die µ-PET-Untersuchungen als auch die Biodistributionsstudien zeigten, dass es bei [68Ga]VN167.MZ zwar zu einer Herzaufnahme kam, die jedoch eher perfusionsabhängig ist. Eine Retention des Tracers im Myokard konnte in geringem Umfang festgestellt werden.

Rock magnetic, element, and color data of three sediment cores along the Senegalese continental margin

We present a suite of new high-resolution records (0-135 ka) representing pulses of aeolian, fluvial, and biogenic sedimentation along the Senegalese continental margin. A multiproxy approach based on rock magnetic, element, and color data was applied on three cores enclosing the present-day northern limit of the ITCZ. A strong episodic aeolian contribution driven by stronger winds and dry conditions and characterized by high hematite and goethite input was revealed north of 13°N. These millennial-scale dust fluxes are synchronous with North Atlantic Heinrich stadials. Fluvial clay input driven by the West African monsoon predominates at 12°N and varies at Dansgaard-Oeschger time scales while marine productivity is strongly enhanced during the African humid periods and marine isotope stage 5. From latitudinal signal variations, we deduce that the last glacial ITCZ summer position was located between core positions at 12°26' and 13°40'N. Furthermore, this work also shows that submillennial periods of aridity over northwest Africa occurred more frequently and farther south than previously thought.

Study of the radioactivity induced in air by a 15-MeV proton beam.

Radioactivity induced by a 15-MeV proton beam extracted into air was studied at the beam transport line of the 18-MeV cyclotron at the Bern University Hospital (Inselspital). The produced radioactivity was calculated and measured by means of proportional counters located at the main exhaust of the laboratory. These devices were designed for precise assessment of air contamination for radiation protection purposes. The main produced isotopes were 11C, 13N and 14O. Both measurements and calculations correspond to two different irradiation conditions. In the former, protons were allowed to travel for their full range in air. In the latter, they were stopped at the distance of 1.5 m by a beam dump. Radioactivity was measured continuously in the exhausted air starting from 2 min after the end of irradiation. For this reason, the short-lived 14O isotope gave a negligible contribution to the measured activity. Good agreement was found between the measurements and the calculations within the estimated uncertainties. Currents in the range of 120–370 nA were extracted in air for 10–30 s producing activities of 9–22 MBq of 11C and 13N. The total activities for 11C and 13N per beam current and irradiation time for the former and the latter irradiation conditions were measured to be (3.60 ± 0.48) × 10−3 MBq (nA s)−1 and (2.89 ± 0.37) × 10−3 MBq (nA s)−1, respectively.

Nitrate-Ammonium Synergism in Rice. A Subcellular Flux Analysis1

Many reports have shown that plant growth and yield is superior on mixtures of NO3− and NH4+ compared with provision of either N source alone. Despite its clear practical importance, the nature of this N-source synergism at the cellular level is poorly understood. In the present study we have used the technique of compartmental analysis by efflux and the radiotracer 13N to measure cellular turnover kinetics, patterns of flux partitioning, and cytosolic pool sizes of both NO3− and NH4+ in seedling roots of rice (Oryza sativa L. cv IR72), supplied simultaneously with the two N sources. We show that plasma membrane fluxes for NH4+, cytosolic NH4+ accumulation, and NH4+ metabolism are enhanced by the presence of NO3−, whereas NO3− fluxes, accumulation, and metabolism are strongly repressed by NH4+. However, net N acquisition and N translocation to the shoot with dual N-source provision are substantially larger than when NO3− or NH4+ is provided alone at identical N concentrations.

Dinoflagellate cysts in surface sediment samples of METEOR cruises M20/2, M23/1, M34/1, M34/2, M34/3 and M34/4

To enhance the limited information available about the palaeo-ecological significance of calcareous dinoflagellates, we have studied their lateral distribution in surface sediments of the equatorial and south Atlantic between 13°N and 36°S. Calcareous dinoflagellate cysts appear to be widely distributed throughout the studied area. In the surface sediments, concentrations (cyst per gram dry sediment) of the vegetative stage Thoracosphaera heimii are generally higher than that of the (presumably) calcareous resting cysts. Distribution patterns in surface sediments of Orthopithonella granifera (Fütterer) Keupp and Versteegh, Rhabdothorax spp. Kamptner., Sphaerodinella albatrosiana (Kamptner) Keupp and Versteegh S. albatrosiana praratabulated, Sphaerodinella tuberosa var. 1 (Kamptner) Keupp and Versteegh and S. tuberosa var. 2 and the ratios between these species have been compared with temperature, salinity, density and stratification gradients in the upper water column. Rhabdothorax spp. is characteristically present in sediments of more temperate regions characterized by high seasonality. Dinoflagellates producing these cysts are able to tolerate high nutrient concentrations, and mixing of the water column. S. albatrosiana is abundant in regions characterized by high sea surface temperatures and oligotrophic surface water conditions. In contrast, the distribution of S. tuberosa var. 2 is negatively related to temperature. The other cyst species did not show a characteristic pattern in relation to the studied environmental gradients. The ratio of Sphaerodinella tuberosa var. 2 to Orthopithonella granifera can be used for reconstructing the presence of stratification in the upper 50 m of the water column, whereas the ratios of S. tuberosa var. 2 to Sphaerodinella albatrosiana and of O. granifera to Rhabdothorax spp. might be used for palaeotemperature reconstructions. Calcareous dinoflagellate cysts are abundant in oligotrophic areas and may be useful for the reconstruction of palaeoenvironmental conditions.

Late Eocene to Early Oligocene magnetostratigraphic chron boundaries of ODP Hole 119-744A (Table 1)

The earliest Oligocene (~33.5 Ma) is marked by a major step in the long-term transition from an ice-free to glaciated world. The transition, characterized by both cooling and ice-sheet growth, triggered a transient but extreme glacial period designated Oi-1. High-resolution isotope records suggest that Oi-1 lasted for roughly 400,000 yr (the duration of magnetochron 13N) before partially abating, and that it was accompanied by an ocean-wide carbon isotope anomaly of 0.75?. One hypothesis relates the carbon isotope anomaly to enhanced export production brought about by climate-induced intensification of wind stress and upwelling, particularly in the Southern Ocean. To understand how this climatic event affected export production in the Southern Ocean, biogenic silica (opal) and carbonate accumulation rates were computed for the sub-polar Indian Ocean using deep-sea cores from ODP Site 744, Kerguelen Plateau. Our findings suggest that net productivity in this region increased by several fold in response to the Oi-1 glaciation. In addition, calcareous primary producers dominant in the Late Eocene were partially replaced by opaline organisms suggesting a trend toward seasonally greater surface divergence and upwelling in this sector of the Southern Ocean. We attribute these changes to intensification of atmospheric=oceanic circulation brought about by high-latitude cooling and the appearance of a full-scale continental ice-sheet on East Antarctica. Higher terrigenous sediment accumulation rates support the idea that wind-induced changes in regional productivity were augmented by an increased supply of glacial dust and debris that provided limiting micro-nutrients (e.g., iron-rich dust particles). We speculate that the rapid changes in biogenic sediment accumulation in the Southern Ocean and other upwelling-dominated regions contributed to the ocean-wide positive carbon isotope anomaly by temporarily increasing the burial rate of organic carbon relative to carbonate carbon. The changes in burial rates, in turn, may have produced a positive feedback on climate by briefly drawing down atmospheric pCO2 .