Bacterial hopanoids as tracers of organic carbon sources and processing across the western Arctic continental shelf

Abstract

Tracing the inputs of bacterial organic carbon to marine systems has been constrained by the lack of distinguishing geochemical tracers and limited contribution in sediments compared to other sources of organic matter. Bacteriohopanepolyols (BHPs) provide a direct means to identify bacterial inputs which also reflect potential bacterial groups and their activities in aquatic systems. We applied recent analytical approaches to identify and quantify bacterial derived carbon contributions to surface sediments from the western Arctic Ocean using BHPs. The abundance and distribution of BHPs resemble trends of water column primary production and suggest active heterotrophic recycling of in situ production with some component of long term preservation. BHPs proposed as terrestrial derived signatures (i.e. adenosylhopanes) were also abundant in western Arctic sediments and reflect offshore trends of other terrigenous lipid signatures with a fraction representing their degradative products. Analysis of BHPs in organic rich peat and surface sediments from two Arctic rivers showed the highest inputs of adenosylhopanes, implying active bacterial recycling of recalcitrant terrigenous material. BHPs observed in western Arctic surface sediments reveal significant contributions of bacteria associated with organic carbon from multiple sources.