10. Seagrass Rhizosphere Microbial Communities

  1. Erik Kristensen,
  2. Ralf R. Haese and
  3. Joel E. Kostka
  1. Richard Devereux

Published Online: 23 MAR 2013

DOI: 10.1029/CE060p0199

Interactions Between Macro- and Microorganisms in Marine Sediments

Interactions Between Macro- and Microorganisms in Marine Sediments

How to Cite

Devereux, R. (2005) Seagrass Rhizosphere Microbial Communities, in Interactions Between Macro- and Microorganisms in Marine Sediments (eds E. Kristensen, R. R. Haese and J. E. Kostka), American Geophysical Union, Washington, D. C.. doi: 10.1029/CE060p0199

Publication History

  1. Published Online: 23 MAR 2013
  2. Published Print: 1 JAN 2005

ISBN Information

Print ISBN: 9780875902746

Online ISBN: 9781118665442

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Keywords:

  • Interactions between macro- and microorganisms in marine sediments

Summary

Seagrasses are aquatic marine angiosperms that exert profound controls on sediment biogeochemistry. Oxygen and organic carbon formed in the leaves during photosynthesis are translocated belowground and released through the roots into the surrounding sediments. This daily pulse stimulates the rhizosphere microbial communities resulting in rates of bacterial production, nitrogen fixation and sulfate reduction being higher in the day than at night. Yet at the same time, end products of microbial respiration, in particular sulfide, can be toxic to the plants if they attain sufficiently high concentrations. Sulfate reduction is the dominant terminal electron-accepting process and is tightly coupled with nitrogen fixation, pointing to the rhizosphere where a synergistic relationship between the plants and sulfate- reducing bacteria is played out. Bacterial numbers and activities are more enriched in seagrass bed sediments than in nearby non-vegetated sediments, and even more so on and within the roots in comparison to bulk vegetated sediments. The distribution and activities of bacteria in seagrass bed sediments suggest a model that distinguishes rhizosphere and root-associated microbial communities responding to root exudates from microbial communities in bulk vegetated sediments degrading organic matter derived from dead roots and rhizomes and from benthic algae and detritus that settles on the surface of seagrass bed sediments.