Symbiont 'bleaching' in planktic foraminifera during the Middle Eocene Climatic Optimum
Symbiont 'bleaching' in planktic foraminifera during the Middle Eocene Climatic Optimum
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DOI：
10.1130/g33388.1
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发表时间：
2013-01-01
期刊：
影响因子：
5.8
通讯作者：
Wilson, P. A.
中科院分区：
文献类型：
--
作者：
Edgar, K. M.;Bohaty, S. M.;Wilson, P. A.
许多现代浮游有孔虫通过寄主光合共生体来适应营养贫乏（寡营养）的地表水，但尚不清楚它们将如何应对未来海洋温度和酸度的变化。本研究表明，大约40 Ma，在中始新世气候最适期（MECO）的短暂全球变暖期间，一些具有光共生体的浮游有孔虫化石暂时“漂白”了它们的共生体。在海洋钻探计划（ODP）站点748和1051（分别为南大洋和中纬度北大西洋），含光共生体的浮游有孔虫测试的大小与其碳同位素比率（δ C-13）之间的典型正相关关系在MECO峰值期间暂时降低了约100 k.y.。与此同时，典型的光共生体浮游有孔虫Acarinina的测试尺寸和相对丰度出现了短暂的减少，表明生态胁迫。最小δ O-18值与试验尺寸δ C-13梯度的减小的重合表明，在MECO期间，海面温度升高与白化之间存在联系，尽管pH值和养分有效性的变化也可能起了作用。我们的研究结果表明，宿主-光共生体的相互作用在地质年代中不是恒定的，这对海洋浮游生物营养策略的进化和共生浮游有孔虫产生的地球化学代理记录的可靠性都有影响。
Many genera of modern planktic foraminifera are adapted to nutrient-poor (oligotrophic) surface waters by hosting photosynthetic symbionts, but it is unknown how they will respond to future changes in ocean temperature and acidity. Here we show that ca. 40 Ma, some fossil photosymbiont-bearing planktic foraminifera were temporarily 'bleached' of their symbionts coincident with transient global warming during the Middle Eocene Climatic Optimum (MECO). At Ocean Drilling Program (ODP) Sites 748 and 1051 (Southern Ocean and mid-latitude North Atlantic, respectively), the typically positive relationship between the size of photosymbiont-bearing planktic foraminifer tests and their carbon isotope ratios (delta C-13) was temporarily reduced for similar to 100 k.y. during the peak of the MECO. At the same time, the typically photosymbiont-bearing planktic foraminifera Acarinina suffered transient reductions in test size and relative abundance, indicating ecological stress. The coincidence of minimum delta O-18 values and reduction in test size-delta C-13 gradients suggests a link between increased sea-surface temperatures and bleaching during the MECO, although changes in pH and nutrient availability may also have played a role. Our findings show that host-photosymbiont interactions are not constant through geological time, with implications for both the evolution of trophic strategies in marine plankton and the reliability of geochemical proxy records generated from symbiont-bearing planktic foraminifera.