Letter | Published:

Variable ageing and storage of dissolved organic components in the open ocean

Nature volume 430, pages 877881 (19 August 2004) | Download Citation



Seawater dissolved organic matter (DOM) is the largest reservoir of exchangeable organic carbon in the ocean, comparable in quantity to atmospheric carbon dioxide1,2. The composition, turnover times and fate of all but a few planktonic constituents of this material are, however, largely unknown3,4. Models of ocean carbon cycling are thus limited by the need for information on temporal scales of carbon storage in DOM subcomponents, produced via the ‘biological pump’, relative to their recycling by bacteria3,4. Here we show that carbohydrate- and protein-like substances in the open Atlantic and Pacific oceans, though often significantly aged, comprise younger fractions of the DOM, whereas dissolved lipophilic material exhibits up to 90 per cent fossil character. In contrast to the millennial mean ages of DOM observed throughout the water column, weighted mean turnover times of DOM in the surface ocean are only decadal in magnitude. An observed size–age continuum further demonstrates that small dissolved molecules are the most highly aged forms of organic matter, cycling much more slowly than larger, younger dissolved and particulate precursors, and directly links oceanic organic matter age and size with reactivity3,5.

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We thank E. Canuel, J. Hwang and S. Griffin for laboratory guidance during compound class extractions; M. Ederington-Hagy, E. Waterson and J. Southon for discussions on experiments; S. Griffin, R. Wilson, L. Delizo, C. Masiello, A. Grottoli and the captains and crews of RV Melville and RV Knorr for field assistance and logistical support; A. McNichol and colleagues at NOSAMS for Δ14C measurements; E. Franks for δ13C measurements; and R. Benner for comments that significantly improved this manuscript. This work was supported by the Chemical Oceanography Program of the US National Science Foundation.

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    • Ai Ning Loh

    Present address: Division of Ecological Studies, College of Arts and Sciences, Florida Gulf Coast University, 10501 FGCU Boulevard South, Fort Myers, Florida 33965, USA


  1. School of Marine Science, College of William and Mary, PO Box 1346, Gloucester Point, Virginia 23062, USA

    • Ai Ning Loh
    •  & James E. Bauer
  2. Department of Earth System Science, University of California at Irvine, 3224 Croul Hall, Irvine, California 92697-3100, USA

    • Ellen R. M. Druffel


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Competing interests

The authors declare that they have no competing financial interests.

Corresponding author

Correspondence to Ai Ning Loh.

Supplementary information

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  1. 1.

    Supplementary Table 1

    This table shows the calculations for the weighted mean turnover times (TOT) for non-homogenously aged reservoirs of dissolved organic matter (DOM) based on the ages of the individual organic and size fractions measured in this study.

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