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

这项提案寻求对Rishi Ram Adhikari(Pi)博士巡航后的研究的支持，他曾作为船上科学家参加IODP 354远征(2015年2月至3月，新加坡-斯里兰卡科伦坡)。在探险期间，沿着8°N穿过孟加拉扇区钻探了7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。这次探险提供了一个人们期待已久的机会，可以在印度洋进行深层生物圈研究。为进行专门的深层生物圈研究，获得了高质量的样本，采用最先进的技术，目的是(A)调查孟加拉扇海底以下微生物群落的规模、组成和活动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有关；(B)阐明有机质来源、溶解有机物质量和深层生物圈新陈代谢过程之间的关系；(C)缩小关于印度洋深层生物圈的巨大数据差距。拟议的研究将检验与IODP科学计划确定的2013-2023年期间基本挑战有关的五个假设，即：海底以下群落的起源、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的敏感度如何？(挑战7)，哪些性质和过程支配着碳在海底的流动和储存？(挑战13)。为此，该项目将通过独立的栽培方法和基于实验室的实验，确定深海海底微生物群落的生物量、活动和组成以及碳周转。调查将包括微生物细胞和内孢子的计数，作为微生物活性替代品的氢酶活性的测定，以及有机代谢物的稳定同位素调查。DOM的组成将使用3D荧光光谱来阐明，微生物群落的组成将使用完整的极性膜脂和DNA来表征。此外，选定的沉积物样品将与稳定同位素标记的(13-C)有机物孵化，以研究孟加拉扇区的碳周转和储存。拟议的研究将在不来梅大学MARUM/Inagaki博士的有机地球化学组(主持人和合作者)和日本高知岩芯样品研究所/JAMSTEC的Fumio Inagaki博士的实验室进行。

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.