Microbial Ecology

, Volume 68, Issue 3, pp 427–440 | Cite as

Changes in Sediment Bacterial Community in Response to Long-Term Nutrient Enrichment in a Subtropical Seagrass-Dominated Estuary

  • Rafael Guevara
  • Makoto Ikenaga
  • Amanda L. Dean
  • Cristina Pisani
  • Joseph N. Boyer
Microbiology of Aquatic Systems


Florida Bay exhibits a natural gradient of strong P limitation in the east which shifts to weak P or even N limitation at the western boundary. This nutrient gradient greatly affects seagrass abundance and productivity across the bay. We assessed the effects of N and P additions on sediment bacterial community structure in relation to the existing nutrient gradient in Florida Bay. Sediment samples from 24 permanent 0.25 m2 plots in each of six sites across Florida Bay were fertilized with granular N and P in a factorial design for 26 months. Sediment bacterial community structure was analyzed using PCR-denaturing gradient gel electrophoresis (DGGE) analysis of 16S ribosomal RNA (rRNA) genes and a cloning strategy from DGGE bands. The phylogenetic positions of 16S rRNA sequences mostly fell into common members found in marine sediments such as sulfate-reducing Deltaproteobacteria, Gammaproteobacteria, Spirochaetes, and Bacteriodetes. Twenty-eight common DGGE bands were found in all sediment samples; however, some DGGE bands were only found or were better represented in eastern sites. Bacterial community diversity (Shannon-Weiner index) showed similar values throughout all sediment samples. The N treatment had no effect on the bacterial community structures across the bay. Conversely, the addition of P significantly influenced the bacterial community structure at all but the most western site, where P is least limiting due to inputs from the Gulf of Mexico. P additions enhanced DGGE band sequences related to Cytophagales, Ectothiorhodospiraceae, and Desulfobulbaceae, suggesting a shift toward bacterial communities with increased capability to degrade polymeric organic matter. In addition, a band related to Deferribacteres was enhanced in eastern sites. Thus, indigenous environmental conditions were the primary determining factors controlling the bacterial communities, while the addition of P was a secondary determining factor. This P-induced change in community composition tended to be proportional to the amount of P limitation obviated by the nutrient additions.


Bacterial Community Bacteroidetes Bacterial Community Structure Deltaproteobacteria Seagrass Community 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.



We wish to thank Jim Fourqurean and Anna Armitage for their permission to sample their field plots and for their ongoing support and suggestions. This research was supported by the National Science Foundation through the Florida Coastal Everglades Long-Term Ecological Research Program (DEB-9910514). This is contribution #667 of the Southeast Environmental Research Center at Florida International University.


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Copyright information

© Springer Science+Business Media New York 2014

Authors and Affiliations

  • Rafael Guevara
    • 1
  • Makoto Ikenaga
    • 2
  • Amanda L. Dean
    • 1
  • Cristina Pisani
    • 1
  • Joseph N. Boyer
    • 1
    • 3
  1. 1.Southeast Environmental Research Center, OE-148Florida International UniversityMiamiUSA
  2. 2.Laboratory of Soil Science, Faculty of AgricultureKagoshima UniversityKagoshimaJapan
  3. 3.Center for the EnvironmentPlymouth State UniversityPlymouthUSA

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