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doi:10.2204/iodp.proc.329.112.2011

KNOX-02RR: drilling site survey—life in subseafloor sediments of the South Pacific Gyre¹

S. D’Hondt,² L.J. Abrams,³ R. Anderson,⁴ J. Dorrance,⁵ A. Durbin,⁶ L. Ellett,⁵ T. Ferdelman,² J. Fischer,⁷ S. Forschner,⁸ R. Fuldauer,⁹ H. Goldstein,⁵ D. Graham,² W. Griffith,¹⁰ H. Halm,⁷ R. Harris,² B. Harrison,¹¹ F. Hasiuk,¹² G. Horn,¹³ J. Kallmeyer,² M. Lever,⁶ J. Meyer,⁵ L. Morse,⁵ C. Moser,¹⁴ B. Murphy,⁵ A. Nordhausen,⁷ L. Parry,⁵ R. Pockalny,⁸ A. Puschell,⁷ J. Rogers,⁸ H. Schrum,⁸ D.C. Smith,⁸ B. Soffientino,⁸ A.J. Spivack,² A. Stancin,¹² M. Steinman,⁹ and P. Walczak¹⁴

Abstract

The middle of the South Pacific Gyre is farther from continents and productive oceanic zones than any other site on Earth. To understand the nature of life in the most oxidized and food-limited subseafloor sediments, Cruise KNOX-02RR surveyed and cored sediment at ten sites throughout the South Pacific Gyre and one site at the southern margin of the gyre. Sediment at all of the South Pacific Gyre sites accumulated extraordinarily slowly for millions of years (0.1–1 m/m.y.).

Shipboard scientific results indicate that South Pacific Gyre sediments contain a living community characterized by very low biomass and very low metabolic activity. At every depth in the cored South Pacific Gyre sediments, cell abundances are 2–6 orders of magnitude lower than at the same depths in all previously explored subseafloor communities. The net rate of respiration by the subseafloor sedimentary community at each gyre site is 1–3 orders of magnitude lower than the rates of subseafloor communities at previously explored sites.

Because of the low rates of respiration, interstitial waters are oxic throughout the upper sediment column in most of this region. Consequently, the subseafloor sedimentary community of this region is predominantly aerobic to more than 8 m below the seafloor, unlike previously explored subseafloor communities. Generation of hydrogen by radiolysis of water may be a significant food source for this subseafloor community.

¹ D’Hondt, S., Abrams, L.J., Anderson, R., Dorrance, J., Durbin, A., Ellett, L., Ferdelman, T., Fischer, J., Forschner, S., Fuldauer, R., Goldstein, H., Graham, D., Griffith, W., Halm, H., Harris, R., Harrison, B., Hasiuk, F., Horn, G., Kallmeyer, J., Lever, M., Meyer, J., Morse, L., Moser, C., Murphy, B., Nordhausen, A., Parry, L., Pockalny, R., Puschell, A., Rogers, J., Schrum, H., Smith, D.C., Soffientino, B., Spivack, A.J., Stancin, A., Steinman, M., and Walczak, P., 2011. KNOX-02RR: drilling site survey—life in subseafloor sediments of the South Pacific Gyre. In D’Hondt, S., Inagaki, F., Alvarez Zarikian, C.A., and the Expedition 329 Scientists, Proc. IODP, 329: Tokyo (Integrated Ocean Drilling Program Management International, Inc.). doi:10.2204/iodp.proc.329.112.2011

² Expedition 329 Scientists’ addresses. Correspondence author: dhondt@gso.uri.edu

³ University of North Carolina at Wilmington, Wilmington NC 28403, USA.

⁴ Carleton College, Northfield Minnesota 55057, USA.

⁵ University of California San Diego, La Jolla CA 92093, USA.

⁶ University of North Carolina at Chapel Hill, Chapel Hill NC 27599, USA.

⁷ Max Planck Institute for Marine Microbiology, Bremen, Germany.

⁸ University of Rhode Island, Narragansett RI 02882, USA.

⁹ Florida Institute of Technology, Melbourne Florida 32901, USA.

¹⁰ Carroll High School, Southlake TX 76092, USA.

¹¹ California Institute of Technology, Pasadena CA 91125, USA.

¹² University of Michigan, Ann Arbor MI 48109, USA.

¹³ University of Southern California, Los Angeles CA 90089, USA.

¹⁴ Oregon State University, Corvallis OR 97331, USA.

Publication: 13 December 2011
MS 329-112

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