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Wednesday, June 22, 2011

R. H. Condon et al., PNAS, Jellyfish blooms result in a major microbial respiratory sink of carbon in marine systems

Proceedings of the National Academy of Sciences, Vol. 108, No. 25, 10225-10230 (June 21, 2011); doi: 10.1073/pnas.1015782108

Jellyfish blooms result in a major microbial respiratory sink of carbon in marine systems

  1. Robert H. Condona,b,1
  2. Deborah K. Steinberga
  3. Paul A. del Giorgioc
  4. Thierry C. Bouvierd
  5. Deborah A. Bronka
  6. William M. Grahamb 
  7. and
  9. Hugh W. Ducklowe
  1. aCollege of William and Mary, Virginia Institute of Marine Science, Gloucester Point, VA 23062;
  2. bDauphin Island Sea Laboratory, Dauphin Island, AL 36528;
  3. cDépartement des Sciences Biologiques, Université du Québec à Montréal, Montreal, QC, Canada H3C 3P8;
  4. dLaboratoire Écosystèmes Lagunaires, UMR5119 Centre National de la Recherche Scientifique-UM2, 34095 Montpellier Cedex 05, France; and
  5. eThe Ecosystems Center, Marine Biological Laboratory, Woods Hole, MA 02543
  1. Edited* by David M. Karl, University of Hawaii, Honolulu, HI, and approved May 11, 2011 (received for review October 20, 2010)


Jellyfish blooms occur in many estuarine and coastal regions and may be increasing in their magnitude and extent worldwide. Voracious jellyfish predation impacts food webs by converting large quantities of carbon (C), fixed by primary producers and consumed by secondary producers, into gelatinous biomass, which restricts C transfer to higher trophic levels because jellyfish are not readily consumed by other predators. In addition, jellyfish release colloidal and dissolved organic matter (jelly-DOM), and could further influence the functioning of coastal systems by altering microbial nutrient and DOM pathways, yet the links between jellyfish and bacterioplankton metabolism and community structure are unknown. Here we report that jellyfish released substantial quantities of extremely labile C-rich DOM, relative to nitrogen (25.6 ± 31.6 C:1N), which was quickly metabolized by bacterioplankton at uptake rates two to six times that of bulk DOM pools. When jelly-DOM was consumed it was shunted toward bacterial respiration rather than production, significantly reducing bacterial growth efficiencies by 10% to 15%. Jelly-DOM also favored the rapid growth and dominance of specific bacterial phylogenetic groups (primarily γ-proteobacteria) that were rare in ambient waters, implying that jelly-DOM was channeled through a small component of the in situ microbial assemblage and thus induced large changes in community composition. Our findings suggest major shifts in microbial structure and function associated with jellyfish blooms, and a large detour of C toward bacterial CO2 production and away from higher trophic levels. These results further suggest fundamental transformations in the biogeochemical functioning and biological structure of food webs associated with jellyfish blooms. 

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