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，因此，不稳定的海底甲烷包合物向大气中大量释放甲烷被假设为过去和可能的未来气候变化的原因（IPCC，2007年）。底栖有孔虫的碳同位素特征，特别是Fontbotia wuellerstorfi，一直被认为是一个代理检测这种笼形物解离引起的气候变化。然而，有孔虫的δ 13 C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，成功实现了必要的实验先决条件：（1）我们建立了一个独特的“高压深海培养实验室”，可以使用新开发的高压釜系统在原始环境中原位（高压）条件下培养活的底栖有孔虫。(2)这是第一次，使甲烷相关的高压培养实验和成功繁殖的嗜压F。wuellerstorfi是古海洋学中最重要的信号载体之一。本实验的目的是：（1）进一步了解甲烷源到有孔虫壳的δ 13 C信号传递过程，（2）通过溶解无机碳的δ 13 C测量，证明有孔虫壳的δ 13 C在多大程度上反映了甲烷源到底层水的生物转化过程;（3）研究食物来源对δ 13 C壳特征的重要性。

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.