4. Belowground Interactions Among Salt Marsh Plants and Microorganisms

  1. Erik Kristensen,
  2. Ralf R. Haese and
  3. Joel E. Kostka
  1. Charles R. Lovell

Published Online: 23 MAR 2013

DOI: 10.1029/CE060p0061

Interactions Between Macro- and Microorganisms in Marine Sediments

Interactions Between Macro- and Microorganisms in Marine Sediments

How to Cite

Lovell, C. R. (2005) Belowground Interactions Among Salt Marsh Plants and Microorganisms, 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/CE060p0061

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

The rhizospheres of salt marsh plants are highly complex, providing physical structural features, carbon substrates, and some key terminal electron acceptors for the root- associated bacteria. While the rhizosphere microbial “black box” is only partially open, substantial progress in understanding important belowground plant-microbe interactions has been made. Diazotrophy (N2 fixation) is a key microbial process in nitrogen-limited salt marshes, and our understanding of both the plant-mediated controls on this process and the surprising diversity of bacterial taxa involved in it have improved substantially. A novel recent finding is that both (O2-utilizing and anaerobic rhizosphere diazotrophs may be active in the same place and time. Sulfate reduction is a dominant process in organic carbon oxidation in vegetated salt marsh sediments. The intimate association of supposed anaerobic sulfate-reducing bacteria with roots that convey O2 from the atmosphere into the rhizosphere illustrates some of the inherent complexity of salt marsh rhizosphere micro-environments. The sulfate-reducing bacteria include significant diazotroph species, likely the most important diazotrophic anaerobes in the rhizosphere. The acetogenic bacteria also illuminate unexpected complexity in the rhizosphere. To date, signature nucleotide sequences of these anaerobes have been recovered from only a single salt marsh plant species, the actively ventilating smooth cordgrass, Spartina alterniflora. Numerous other belowground salt marsh plant-associated microbial activities remain relatively unex-plored. Unraveling belowground plant-microbe interactions and discovery of key micro- bial “hidden players” may improve the success of efforts to remediate and restore these productive but fragile ecosystems.