Particulate organic matter sinks and sources in high Arctic fjord

- Terrestrial POC input to Kongsfjorden of 760 · 106 g y− 1 originates mostly from glaciers.
- Organic carbon burial rate amounts to 9-13 g Corg m− 2 y− 1 in Kongsfjorden.
- Marine δ13Corg end member has a very broad range in the high Arctic.
- Tracing of terrestrial OM by δ13Corg is limited in marine regions of the high Arctic.

The main aim of this paper is to present results on concentrations, fluxes and isotopic composition (δ13Corg) of particulate and sedimentary organic carbon (measures of particulate and sedimentary organic matter, respectively) in Kongsfjorden, Spitsbergen. The terrestrial particulate organic carbon (POC) input to the Kongsfjorden reached 760 · 106 ± 145 · 106 g Corg y− 1, forced mostly by the glaciers' activity. This constituted 5-10% of the bulk POC supplied to the system. Marine primary production was the main source of the remaining 90-95% of POC. Organic carbon burial rates amounted to 9 ± 1 g Corg m− 2 y− 1 in the central and 13 ± 1 g Corg m− 2 y− 1 in the outer part of the fjord. Two terrestrial POM δ13Corg end members were identified: the ancient organic matter (OM) supplied by glaciers and rivers fed by water discharged from the glaciers (from − 25.4‰ to − 25.1‰), and the fresh terrestrial POM (from − 26.7‰ to − 26.6‰). Marine OM was characterized by a wide range of δ13Corg signatures: from ≤ − 26.1‰ for the phytoplankton depleted in 13Corg to ca. − 15.8‰ for debris of marine phytobenthos. The lack of distinct marine δ13Corg end member and the resemblance of phytoplankton δ13Corg signatures to the terrestrial POM δ13Corg end member precluded the use of the two δ13Corg end member mixing model to trace the terrestrial OM in Kongsfjorden, which is also very likely to happen in other Arctic regions.