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

“印度洋海平面、海流和季风演变”科考队359号将调查马尔代夫海脊，它向南延伸穿过印度洋，是一个双链珊瑚环礁。这些环礁位于一个火山脊上，这个火山脊是在印度板块向北移动时在地幔热点上形成的。随着脊冷却下来，它在海面上被一连串的环礁和环礁之间更深的海槽所取代。在这些海槽中，来自海脊的厚厚碳酸盐沉积物与开阔的海洋沉积物混合在一起。这些沉积物提供了一个独特的机会来研究开放海洋浮游碳酸盐和浅海碳酸盐之间的关系，这通常是难以比较的。该项目旨在利用这一机会，看看产生颗石藻的远洋碳酸盐变化与浅海碳酸盐系统之间是否存在一致的相关性。如果这种相关性确实存在，它将提供强有力的证据，证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强烈的影响。相反，如果没有观察到这样的联系，那么就会对诸如球石藻丰度或钙化的变化被解释为由非生物因素引起的程度提出质疑。演替的巨大厚度也意味着浮游生物组合的突变间隔可以用比通常可能的更高的分辨率来研究。这将提供测试这些变化是否由环境事件引起的机会。该项目将特别关注球石藻的优势群——网纹石属的大小变化。该组显示出长期的尺寸减小，但这是由一系列突然的尺寸减小事件形成的，这些事件被延长的尺寸增大间隔分隔开。这将是第一次在一个地方系统地研究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代用物的变化或浅海碳酸盐体系的变化有关。

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.