Development and N2-Fixing Activity of the Benthic Microbial Community in Transplanted Spartina alterniflora Marshes in North Carolina |
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| Authors: | M F Piehler C A Currin R Cassanova & H W Paerl |
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| Institution: | Institute of Marine Sciences, The University of North Carolina at Chapel Hill, 3431 Arendell Street, Morehead City, NC 28557, U.S.A.,;NOAA-NMFS, Beaufort Laboratory, Beaufort, NC 28516, U.S.A.,;The University of North Carolina at Pembroke, Pembroke, NC 28372, U.S.A. |
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| Abstract: | Growth and maturation of transplanted salt marshes is often limited by the availability of nitrogen (N). We examined the role of N2-fixing benthic microbial assemblages (microalgae and associated bacteria) in two restored marshes (1-year-old and 6-year-old marsh) and a natural salt marsh in the Newport River Estuary, North Carolina. Benthic N2 fixation (nitrogenase activity, NA), chlorophyll a (Chl a ) concentration, Spartina alterniflora (smooth cordgrass) stem counts, and sediment organic matter content were determined in the three marshes. Significant differences were observed between sites for both Chl a and NA. The 1-year-old marsh always exhibited the highest levels of NA and Chl a . Sediment organic matter content was lowest in the 1-year-old marsh (～2%), intermediate in the 6-year-old marsh (～5%), and highest in the natural marsh (～10%). Carbon and nitrogen analyses were also performed on the 1-year-old marsh sediments, which were depleted in N. A positive correlation was observed between surface sediment N and Chl a . Remineralized, microbially derived N may provide growth-limiting inorganic N to Spartina transplants. N2-fixing microbial assemblages in the 1-year-old marsh may also be an important food source for marsh infauna. Benthic N2-fixing microbial assemblages play a key role in the N economy of restored salt marshes. |
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