Diversity of nifH Genotypes in Floating Periphyton Mats Along a Nutrient Gradient in the Florida Everglades |
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Authors: | Puja Jasrotia Andrew Ogram |
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Institution: | (1) Soil and Water Science Department, University of Florida, P.O. Box 110290, Gainesville, FL 32611-0290, USA;(2) Present address: Environmental Sciences Institute, Florida A&M University, 1515 South MLK Blvd., 305 FSHSRC, Tallahassee, FL 32307, USA |
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Abstract: | Periphyton mats are an important component of many wetland ecosystems, performing a range of vital ecosystem functions, including
nitrogen fixation. The composition and integrity of these mats are affected by nutrient additions, which might result in changes
in their function. The overall objective of this study was to investigate the distribution of nifH sequences in floating periphyton mats collected along a nutrient gradient in the Florida Everglades. Distribution of nifH clone libraries indicated nutrient enrichment selected primarily for sequences branching deeply within the heterocystous
cyanobacteria and within a novel group of cyanobacteria; sequences from low-nutrient sites were broadly distributed, with
no clear dominance of sequences associated with heterocystous and nonheterocystous cyanobacteria and alpha-, gamma-, and delta-proteobacteria.
The dominance of heterocystous cyanobacteria in nutrient-enriched sites and the lack of clear dominance by heterocystous cyanobacteria
is consistent with previously reported diurnal cycles of nitrogen fixation rates in these systems. Sequences clustering with
those harbored by methanotrophs were also identified; sequences from nutrient-impacted and transition regions clustered with
those characteristic of type II methanotrophs, and sequences from oligotrophic regions clustered with type I methanotrophs. |
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