Is evolution of calcareous phytoplankton related to shallow marine carbonate system dynamics?

IOPD探险359，海平面、洋流和印度洋季风演变将调查马尔代夫海脊，它向南延伸穿过印度洋，形成一个双珊瑚环礁链。这些环礁位于印度板块向北移动时在地幔热点上方形成的火山山脊上。随着海脊的冷却，海脊下沉，在表面被环礁和环礁之间更深的海槽取代。在这些海槽中，来自海脊的巨大厚度的碳酸盐沉积物与远洋沉积物混合在一起。这些沉积物为研究公海浮游碳酸盐和浅海碳酸盐之间的关系提供了一个独特的机会--这两种碳酸盐通常很难进行比较。该项目试图利用这一机会，看看产生球石的远洋碳酸盐与浅海碳酸盐系统的变化之间是否存在任何一致的相关性。如果这种关联真的发生了，它将提供强有力的证据，表明温度和海水化学等非生物因素对这些系统的大规模演化有很强的影响。相反，如果没有观察到这样的联系，就会产生疑问，例如球藻丰度或钙化的变化在多大程度上被解释为非生物因素造成的。序列的巨大厚度也意味着可以以比通常可能的更高的分辨率来研究浮游生物组合的突然变化的间隔。这将提供机会来测试这种变化是否是由环境事件引起的。该项目将特别侧重于球虫体的主要群体--网状雌虫--的大小变化。这一组显示了长期的尺寸减小，但这是由一系列突然的尺寸减小事件形成的，这些事件被尺寸增大的延长间隔隔开。这将是第一次在一个地方系统地研究从中新世中期到最近的一系列尺寸减小事件，并测试它们是否与环境指标的变化或浅海碳酸盐系统的变化相关联。

IOPD Expedition 359, Sea Level, Currents, and Monsoon Evolution in the Indian Ocean will be investigating the Maldives Ridge which stretches southward through the Indian Ocean as a double chain of coral atolls. These atolls lie along a volcanic ridge which formed over a mantle hotspot as the Indian plate moved northwards. As the ridge cooled it subsided to be replaced at the surface by the string of atolls and between them deeper troughs.Within these troughs vast thicknesses of carbonate sediments derived from the ridge have built up intermixed with open ocean sediments. These sediments provide a unique opportunity to examine the relationships between open ocean planktonic carbonates and shallow marine carbonates - which normally are difficult to compare. This project seeks to exploit this opportunity to see whether there are any consistent correlations between changes in the pelagic carbonate producing coccolithophores and the shallow marine carbonate system. If such correlations do occur it will provide strong evidence that abiotic factors such as temperature and sea water chemistry have strong influences on large scale evolution of these systems. Conversely if no such linkages can be observed it will cal into question the degree to which changes in for instance coccolithophore abundance or calcification are interpreted as being caused by abiotic factors.The great thicknesses of the successions also mean that intervals of abrupt change in plankton assemblages can be studied at higher resolution than is normally possible. This will provide the opportunity to test if such changes are caused by environmental events. The project will specifically focus on size variation in the dominant group of coccolithophores the reiticulofenestrids. This group shows a long term size reduction but this is formed of series of abrupt size reduction events separated by extended intervals of size increase. This will be the first time the set of size reduction events from the middle Miocene to the recent have been studied systematically in one place as well as testing to see if they correlate with change in environmental proxies or changes in the shallow marine carbonate system.