Tracking Organic Carbon Sources and Sequestration in Lake Sediments through the Holocene at a NE Atlantic Peatland Catchment

A critical component of the carbon cycle is carbon sequestration, a process that effectively removes carbon from the atmosphere on a timescale from centuries to millennia. Sequestration can take several biogeochemical forms, but one of the largest carbon pools is long-term storage in sediments or soil. Quantifying the amount and sources of carbon that enters the lake sediment is a less understood aspect of the carbon cycle, and represents an important emerging topic in lacustrine studies. Many studies that investigate carbon sequestration in aquatic sediments focus on the recent past, providing context to short-term changes. In order to provide insight into the more distant past, an 8m long sediment core was extracted from Lough Feeagh, Co. Mayo, Ireland. Physical and geochemical analyses were conducted on the core, including 14C AMS radiocarbon dating, stable isotope analysis (δ13C, δ15N), ramped pyroxidation, elemental C and N, bulk density and organic matter content. In addition, bathymetry/sub-bottom profiling was conducted to determine sediment depth across the lake. Sediment accumulation rates and sediment volume were calculated and used to provide an estimation of organic carbon accumulation at Lough Feeagh. Our results indicate that Lough Feeagh continually accumulated carbon throughout the Holocene. More recent increases in accumulation rates were found that were similar to those seen elsewhere over the past 150 years. These results provide further insights into the role of lakes in the carbon cycle, and context for future changes.