Capturing Carbon in the Dark Ocean


Contributions to the carbon cycle in the ocean’s water column below the penetration of sunlight have not yet been explained either mechanistically or quantitatively, although a significant part of ocean carbon fixation is known to be due to microbial activities. Current oceanographic models suggest that archaea, the prevalent microbial domain in the oceans, do not adequately account for the carbon that is being fixed in the dark ocean. New research using sequencing technology has identified microbes involved in capturing carbon in the twilight zone, the region of the ocean that lies between 200 meters and 1,000 meters beneath the surface. This study discovered specific types of bacteria (the other domain of prokaryotic microbes besides the archaea) that may be responsible for this major, previously unrecognized component of the dark ocean carbon cycle. The report’s authors isolated and identified bacteria from water samples collected in the South Atlantic and North Pacific oceans. They found that “…previously unrecognized metabolic types of dark ocean bacteria may play an important role in global biogeochemical cycles, and their activities may in part reconcile current discrepancies in the dark ocean’s carbon budget.” A better model of carbon cycling in the oceans will help experts predict future CO2 concentrations in the atmosphere and oceans and impacts of altered CO2 fluxes on ocean biogeochemistry. This work involved researchers from the DOE Joint Genome Institute.


Swan, B., et al. 2011. “Potential for Chemolithoautotrophy Among Ubiquitous Bacteria Lineages in the Dark Ocean,” Science 333, 1296-1300. DOI: 10.1126/science.1203690.