Salt marshes are dynamic environments, having complex zonation and community structure governed by changes in salinity, water level, and temperature. Salt marshes are dominated by rooted vegetation and are some of the most productive ecosystems in the world, producing up to 3000 g C/m²/y. Most of the energy transformations in salt marshes are carried out by microbes. In salt marsh sediments, nitrogen and sulfur cycles influence all of the salt marsh biogeochemical cycles, while sulfate reduction dominates decomposition. In this project, scientists from Woods Hole Oceanographic Institute, the Marine Biological Laboratory, and the University of Washington are collaborating to study microbes involved in the nitrogen and sulfur cycles, using a suite of tools including culturing, molecular detection and identification, and process rate measurements.

As part of a Microbial Observatory project, we have established several sampling sites in Plum Island Sound, which is a Long Term Ecological Research (LTER) Site in northeastern Massachusetts. The sampling sites cover a range of salinities, and include sites inhabited by the cordgrass, Spartina, as well as unvegetated sites. Specific objectives are

1. to identify the microbes by culturing and sequencing techniques,
2. to investigate the seasonal changes in the community structure of sulfate reducing bacteria and nitrifying bacteria,
3. to link functional genes with microbial populations, and
4. to correlate presence and activity of specific microbial populations with measurements of major processes in the salt marsh.

Salt marshes continue to be important models for basic microbiological and biogeochemical research. Their high process rates, large and diverse populations of functionally distinct microbes, and steep chemical and physical gradients allow scientists to understand how microbial interactions and chemical cycles work.

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