Hydrothermal Vents Are a Source of Old Refractory Organic Carbon to the Deep Ocean

Based on the C‐14 data of Druffel et al. (2021, https://doi.org/10.1029/2021gl092904) along the Eastern Pacific Rise, dissolved organic carbon (DOC) in the deep ocean is old and thus refractory. Their data in combination with previous He‐3 data indicate that the source of this aged DOC is from the hot waters emanating from hydrothermal vents along the ridge axis. The isotopic and structural composition of the source DOC is unknown, which requires a concerted effort by the marine organic chemistry community to elucidate these chemical forms. Plain Language Summary The age of the dissolved organic carbon (DOC) in the deep ocean has been ascertained by the C‐14 radioisotope, and it is older than 6,000 years. The only significant source that can account for this is seawater passing through the ocean crust and spewing from hydrothermal vents. However, the chemical composition of this refractory or difficult to degrade DOC is unknown. Key Points Hydrothermal vent fields are a source of old and refractory dissolved organic carbon (DOC) to the deep ocean There is scant information on the concentration and chemical structures of DOC from vents Radiocarbon data are needed on DOC emanating from the hot waters of hydrothermal vents