Culture experiments on the gamma 13C values recorded in tests of benthic foraminifera from methane sources at high latitudes

由于甲烷是一种强大的温室气体，从不稳定的海底甲烷笼合物向大气中大量排放甲烷被假设为过去和可能未来气候变化的原因(IPCC，2007)。底栖有孔虫的碳同位素特征，特别是Wellerstorfi有孔虫的碳同位素特征，被认为是检测这种笼状解离引起的气候变化的替代。然而，有孔虫的δ13C特征在多大程度上反映了甲烷的释放，这一点从未得到实验验证。这就是这个项目的目标。在本次资助期间，我们成功地达到了必要的实验前提条件：(1)我们建立了一个独特的“高压深海养殖实验室”，允许使用新开发的高压灭菌器系统，在原始环境中原位(高压)条件下培养活的海底有孔虫。(2)首次实现了甲烷高压培养实验和古海洋学中最重要的信号载体之一--高压菌的成功繁殖。我们未来的实验旨在(1)提高我们对δ13C信号从甲烷源转移到有孔虫贝壳的过程的理解；(2)有孔虫δ13C在多大程度上反映了从甲烷源到底水的生物转化，这是通过溶解的无机碳的δ13C来衡量的；以及(3)检查食物来源对δ13C贝壳信号的重要性。

Since methane is a powerful greenhouse gas, significant releases of methane from instable submarine CH4 clathrates into the atmosphere have been hypothesized as a cause of past and possibly future climate changes (IPCC, 2007). The carbon isotope signature of benthic foraminifers, especially that of Fontbotia wuellerstorfi, has been considered a proxy to detect such clathrate dissociation induced climate changes. However, it has never been experimentally verified to what extent the foraminiferal δ13C signature reflects the release of methane. This is the goal of this project. The necessary experimental preconditions were successfully achieved during the current grant: (1) We established a unique “high-pressure deep-sea cultivation laboratory” that allows culturing living benthic foraminifers in their original surrounding environment under in-situ (high-pressure) conditions using a newly developed autoclave system. (2) For the first time, this enabled both methane-related high-pressure cultivation experiments and successful reproduction of barophilic F. wuellerstorfi, one of the most important signal-carrier in palaeoceanography. Our future experiments are designed to (1) improve our understanding about the process of δ13C signal transfer from the methane source into the foraminiferal shell; (2) document to what extent the foraminiferal δ13C reflects the biological conversion from the CH4 source into the bottom water, which is measured by the δ13C of the dissolved inorganic carbon; and (3) examine the importance of the food source on the δ13C shell signature.