Porewater dissolved organic carbon and associated geochemical data for methane seeps in the Cascadia Margin: Astoria Canyon, Barkley Canyon, Hydrate Ridge, and Bullseye Vent

These data include vertical profiles of concentrations and stable carbon isotope values of dissolved organic carbon (DOC), dissolved inorganic carbon (DIC), total organic carbon (TOC) from sediment cores collected at methane seeps and reference sites. Sediment porosity and dissolved sulfate and methane concentrations are also presented. Methane seeps in Astoria Canyon, Barkley Canyon, Hydrate Ridge, and Bullseye Vent, along the Cascadia Margin, were sampled. These data were collected over two decades and across four cruises: PGC02-08 (CCGS John P. Tully, 2002), Hydrates 2004 Sea Trial (CCGS John P. Tully, 2004), AT50-14 (R/V Atlantis, 2023),  and AT50-29B (R/V Atlantis, 2024).

These data are used to assess the prevalence of methane-derived DOC at methane seeps, which may contribute ‘old’ carbon to the deep ocean or serve as a source of reduced carbon for the deep ocean microbial loop.