Subseafloor life and carbon cycling in the Bengal Fan (IODP Exp. 354)

该提案寻求对 Rishi Ram Adhikari 博士（PI）的航后研究的支持，他曾在 IODP 354 次远征（2015 年 2 月至 3 月，新加坡-科伦坡，斯里兰卡）中担任船上科学家。在探险期间，沿北纬 8° 横跨孟加拉扇钻探了七个地点，以研究构造、气候变化和全球碳循环之间的相互作用。这次探险提供了人们渴望已久的在印度洋进行深层生物圈研究的机会。采用最先进的技术，为专门的深层生物圈研究获得了高质量样本，旨在（a）研究孟加拉扇海底微生物群落的大小、组成和活性如何与扇演化过程中沉积物通量和有机质质量的长期和短期变化相关，（b）阐明深层生物圈中有机质来源、溶解有机物（DOM）质量和代谢过程之间的关系，以及（c）减少有关深层生物圈的巨大数据差距在印度洋。拟议的研究将测试与 IODP 科学计划 (ISP) 2013-2023 年期间确定的基本挑战相关的五个假设，即：海底生物群落的起源、组成和全球意义是什么？ （挑战5），生态系统和生物多样性对环境变化有多敏感？ （挑战 7）以及哪些特性和过程控制着海底下碳的流动和储存？ （挑战 13）。为此，该项目将通过独立培养方法和基于实验室的实验来确定微生物群落的生物量、活性和组成以及海底深处的碳周转率。研究将包括微生物细胞和内生孢子的计数、作为微生物活性代表的氢化酶活性的测定以及有机代谢物的稳定同位素研究。 DOM 的组成将使用 3D 荧光光谱进行阐明，微生物群落的组成将使用完整的极性膜脂和 DNA 进行表征。此外，选定的沉积物样本将与稳定同位素标记的 (13-C) 有机物一起孵育，以研究孟加拉扇中的碳周转和储存。拟议的研究将在不来梅大学 MARUM 的 Kai-Uwe Hinrichs 教授（主持者和合作者）的有机地球化学小组以及日本高知核心样本研究所/JAMSTEC 的 Fumio Inagaki 博士（合作者）的实验室中进行。

This proposal seeks support for post-cruise research of Dr. Rishi Ram Adhikari (PI), who has sailed as shipboard scientist on IODP Expedition 354 (February-March 2015, Singapore-Colombo, Sri Lanka). During the expedition seven sites were drilled across the Bengal Fan along 8°N to study interactions between tectonics, climate change and the global carbon cycle. The expedition provided a much longed-for opportunity to conduct deep biosphere research in the Indian Ocean. High-quality samples were obtained for dedicated deep biosphere research with state-of-the-art techniques aiming to (a) investigate how the size, composition and activity of subseafloor microbial communities in the Bengal Fan are related to long- and short-term changes in sediment flux and OM quality during the evolution of the fan, (b) elucidate relationships between the sources of OM, dissolved organic matter (DOM) quality and metabolic processes in the deep biosphere and (c) reduce the large data gap regarding the deep biosphere in the Indian Ocean. The proposed study will test five hypotheses related to fundamental challenges identified in the IODP Science Plan (ISP) for the period 2013-2023, i.e.: What are the origin, composition, and global significance of subseafloor communities? (Challenge 5), How sensitive are ecosystems and biodiversity to environmental change? (Challenge 7), and What properties and processes govern the flow and storage of carbon in the subseafloor? (Challenge 13). To this end, the project will determine biomass, activity and composition of microbial communities as well as carbon turnover in the deep subseafloor with both cultivation independent methods and laboratory based experiments. Investigations will encompass enumeration of microbial cells and endospores, determination of hydrogenase enzyme activity as proxy for microbial activity, and stable isotopic investigation of organic metabolites. The composition of DOM will be elucidated using 3D fluorescence spectroscopy and microbial community compositions will be characterized using intact polar membrane lipids and DNA. Moreover, selected sediment samples will be incubated with stable isotope labeled (13-C) organic matter to study carbon turnover and storage in the Bengal Fan. The proposed research will be conducted in the Organic Geochemistry Group of Prof. Dr. Kai-Uwe Hinrichs (host and collaborator) at MARUM/University of Bremen and in the laboratory of Dr. Fumio Inagaki (collaborator) at the Kochi Institute for Core Sample Research/JAMSTEC in Japan.