Sources of sedimentary organic matter in Arctic fjords: Evidence from lipid molecular markers

Abstract

The identification of the origin of organic matter in Arctic fjord systems is especially challenging due to complex and highly variable environmental settings, which are impacted by ongoing rapid climate changes. In this study we use a multiproxy approach based on various lipid biomarkers to investigate the provenance of organic matter deposited in surface sediments in the four high-Arctic fjords located in the western part of Spitsbergen (Hornsund, Adventfjorden, Kongsfjorden, and Raudfjorden). This work focuses on the analyses of several classes of lipid biomarkers such as n-alkanes, saturated cyclic hydrocarbons (hopanes, steranes), highly branched isoprenoid (IP25 – ice proxy), alkenones and polar steroids, including sterols and stanols. The findings of this research indicate the occurrence of sedimentary organic matter derived from multiple marine and land-based sources in the studied fjords. The analysis of biomarkers reveals pronounced differences between fjords located in southern and northern parts of western Spitsbergen with regard to contributions of sedimentary organic matter derived from biogenic sources (phytoplankton, animal-derived material as well as terrestrial vascular plants), relative abundances of specific phytoplankton genera (diatoms vs. dinoflagellates), and intensity of bio-advection (Emiliania huxleyi) related to inflows of warm Atlantic Water. The uncommon n-alkane profiles, especially in the short-chain range, reported for investigated sediments are likely to reflect probable contributions related to ancient organic matter and/or microbial sources/activities. To our knowledge, this is the first such comprehensive research on the origin of organic matter deposited in surface sediments from the western Spitsbergen fjords, based on lipid molecular biomarkers.