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SEAGRASS RHIZOSPHERE MICROBIAL COMMUNITIES
Citation:
Devereux, R D. SEAGRASS RHIZOSPHERE MICROBIAL COMMUNITIES. Chapter 10, American Geophysical Union, Washington, DC, , 199-216, (2005).
Impact/Purpose:
To study the distribution and activities of rhizosphere microbial communities in seagrass beds
Description:
Devereux, Richard. 2005. Seagrass Rhizosphere Microbial Communities. In: Interactions Between Macro- and Microorganisms in Marine Sediments. E. Kristense, J.E. Kostka and R.H. Haese, Editors. American Geophysical Union, Washington, DC. p199-216. (ERL,GB 1213).
Seagrasses are aquatic marine angiosperms that exert profound controls on sediment biogeochemistry. Oxygen and carbon formed in the leaves during photosynthesis is translocated below ground and released through the roots into the surrounding sediments. This daily pulse stimulates the 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 the sulfate-reducing bacteria is played out. Bacterial numbers and activities are enriched in seagrass bed sediments over nearby non-vegetated sediments, and are even more so on and within the roots in comparison to bulk vegetated sediments. The distribution and activities of bacteria in seagrass bed sediments suggests 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 benthic and pelagic algae that settles on the surface of seagrass bed sediments.