Trophic Changes off Southwest Greenland During the Holocene and Their Influence on Carbon Burial

Abstract Organic carbon (OC) burial in sediments is partly controlled by catabolic biodegradation and remineralization by heterotrophic bacteria, but long‐term records of these bacterially‐mediated processes have not been available. Here, we use stable hydrogen isotope ratio of the saturated C 16 fatty acid (δ 2 H C16:0 ) as a proxy of the prevalence of heterotrophic bacterial activity to reconstruct the history of Holocene OC biodegradation and remineralization from a sediment core recovered on the southwest Greenland Shelf. A positive shift in the δ 2 H C16:0 during the Holocene Thermal Maximum indicates increased inputs of heterotrophic bacterial biomass to sediments. This implies efficient biodegradation and remineralization of OC during this warm period that are linked to low sediment accumulation rates (SARs) and elevated primary productivity. We propose that enhanced bacterial catabolism of OC in the absence of increased SARs will reduce OC burial efficiency in warmer, high‐latitude oceans, thereby providing positive feedback to climate warming.