AME 60:273-287 (2010)  -  doi:10.3354/ame01427

Oceanic heterotrophic bacterial nutrition by semilabile DOM as revealed by data assimilative modeling

Ya-Wei Luo1,2,6,*, Marjorie A. M. Friedrichs3, Scott C. Doney4, Matthew J. Church5, Hugh W. Ducklow1,2

1The Ecosystems Center, Marine Biological Laboratory, 7 MBL Street, Woods Hole, Massachusetts 02543, USA
2Department of Ecology and Evolutionary Biology, Brown University, Providence, Rhode Island 02912, USA
3Virginia Institute of Marine Science, College of William and Mary, PO Box 1346, Gloucester Point, Virginia 23062, USA
4Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, MS#25, Woods Hole, Massachusetts 02543, USA
5School of Ocean and Earth Science and Technology, University of Hawaii, 1000 Pope Road, Honolulu, Hawaii 96822, USA
6Present address: Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, MS#25, Woods Hole, Massachusetts 02543, USA
*Email:

ABSTRACT: Previous studies have focused on the role of labile dissolved organic matter (DOM) (defined as turnover time of ~1 d) in supporting heterotrophic bacterial production, but have mostly neglected semilabile DOM (defined as turnover time of ~100 to 1000 d) as a potential substrate for heterotrophic bacterial growth. To test the hypothesis that semilabile DOM supports substantial amounts of heterotrophic bacterial production in the open ocean, we constructed a 1-dimensional epipelagic ecosystem model and applied it to 3 open ocean sites: the Arabian Sea, Equatorial Pacific and Station ALOHA in the North Pacific Subtropical Gyre. The model tracks carbon, nitrogen and phosphorus with flexible stoichiometry. This study used a large number of observations, including measurements of heterotrophic bacterial production rates and standing stocks, and DOM concentration data, to rigorously test and constrain model output. Data assimilation was successfully applied to optimize the model parameters and resulted in simultaneous representation of observed nitrate, phosphate, phytoplankton and zooplankton biomass, primary production, heterotrophic bacterial biomass and production, DOM, and suspended and sinking particulate organic matter. Across the 3 ocean ecosystems examined, the data assimilation suggests semilabile DOM may support 17 to 40% of heterotrophic bacterial carbon demand. In an experiment where bacteria only utilize labile DOM, and with more of the DOM production assigned to labile DOM, the model poorly represented the observations. These results suggest that semilabile DOM may play an important role in sustaining heterotrophic bacterial growth in diverse regions of the open ocean.


KEY WORDS: Heterotrophic bacteria · Semilabile dissolved organic matter · Marine ecosystem model · Data assimilation


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Cite this article as: Luo YW, Friedrichs MAM, Doney SC, Church MJ, Ducklow HW (2010) Oceanic heterotrophic bacterial nutrition by semilabile DOM as revealed by data assimilative modeling. Aquat Microb Ecol 60:273-287

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