MEPS 267:45-56 (2004)  -  doi:10.3354/meps267045

Production of chromophoric dissolved organic matter (CDOM) in the open ocean by zooplankton and the colonial cyanobacterium Trichodesmium spp.

Deborah K. Steinberg1,*, Norman B. Nelson2, Craig A. Carlson3, Anne Prusak4

1Department of Biological Sciences, Virginia Institute of Marine Science, PO Box 1346, Gloucester Point, Virginia 23062, USA
2Institute for Computational Earth System Science, University of California Santa Barbara, Santa Barbara, California 93106, USA
3Department of Ecology, Evolution, and Marine Biology, University of California Santa Barbara, Santa Barbara, California 93106, USA
4School of Biology, Georgia Institute of Technology, Atlanta, Georgia 30332, USA

ABSTRACT: Chromophoric (or colored) dissolved organic matter (CDOM) has been identified as a major determinant of the optical properties of oligotrophic oceans. The factors controlling distribution of CDOM far from the direct influence of land are not well known, as CDOM abundance and distribution does not directly correlate with phytoplankton productivity or biomass, or with dissolved organic matter (DOM) concentration. As part of a larger study of the dynamics of CDOM in the open ocean, we investigated direct release from plankton as a factor contributing to distribution patterns of CDOM. We measured the production of CDOM by zooplankton (copepods, euphausiids, amphipods, salps, polychaetes), protozoans (colonial radiolaria), and by the colonial cyanobacterium Trichodesmium spp. in the North Atlantic subtropical gyre. Groups of individual species of plankton were incubated and absorption spectra were obtained for their release products. CDOM was produced by all organisms examined, and absorption spectra varied by taxa, with major taxa exhibiting characteristic absorption peaks. Plankton-produced DOM is a source of labile carbon facilitating microbial activity, and CDOM may also serve as photoprotection for near-surface-living organisms. Zooplankton likely play an important role in the CDOM cycle in the Sargasso Sea, directly through release/excretion of CDOM and indirectly by providing a labile substrate (excretia) for microbial-mediated production of CDOM.

KEY WORDS: Zooplankton · Trichodesmium · Chromophoric dissolved organic matter · (CDOM) Excretion · Sargasso Sea · North Atlantic

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