Heterotrophic life is fueled by organic material, and Total Organic Carbon (TOC) content has been linked to the distribution of biomass and cell abundance in marine sediments. However, the lability of the available organic material is critical for the respiratory activity and the growth yield of microbial communities. In this study, we present results from a novel pyrolytic approach called Extended Slow Heating (ESH) that provides detailed information on the thermal behavior of different subfractions of organic carbon. The approach is applied to sediments recovered from undisturbed abyssal settings and perturbed complex hadal trench sediments. Using a mathematical model to analyze the pyrolysis data, we show that subfractions of easily degradable organic material better describe the distribution of microbial communities as compared to TOC, which presumably was dominated by resilient organic material. Our results highlight the limitations of using TOC as a predictor for the distribution of microbial life in deep ocean sediments and emphasize the need for more detailed analyses that characterize the nature of the organic material in order to understand the distribution of microbial communities. These findings have important implications for the evaluation of organic matter lability, and the understanding of the processes controlling the preservation and transformation of organic matter in marine sediments.

Primary Presenter: Marco Sindlev, University of Southern Denmark (marcos@biology.sdu.dk)

Authors:

Hamed Sanei, Aarhus University, Denmark  ()

Arka Rudra, Aarhus University, Denmark  ()

Donald Canfield, University of Southern Denmark  ()

Ronnie Glud, University of Southern Denmark  ()