Extracellular Polymeric Substances of Everglades Periphyton Mats: Role in Calcium Carbonate Deposition

(Collaborators: Scot Hagerthey and Brent Bellinger)
       Periphyton mats are a dominant, widespread component of sloughs throughout the unenriched Everglades ecosystem.  The communities represent a rich consortium of cyanobacteria, eukaryotic phototrophs along with abundant bacteria and invertebrates.  While it was known that the periphyton mats are held together by polymers secreted by the algal component of the periphyton mats, no previous work has characterized the biochemical nature of these polymers.  Preliminary data indicates that the polymers are carbohydrate rich heteropolymers with varying content of uronic acid residues.  Compositional variations in the EPS were observed between periphyton mats dominated by cyanobacteria/diatoms and desmid/diatom mats.  EPS content was greater than that typically observed in estuarine biofilms, communities known to contribute to sediment stabilization and as a large carbon pool for heterotrophic organisms.  Ecological functions within the Everglades are hypothesized to be similar, and the biochemical data gathered by our initial investigations have begun to shed light on the functional role of EPS in Everglades biofilms.

      One of the most interesting phenomena of periphyton mats in the Everglades is their ability to precipitate calcium carbonate.  Given specific water quality conditions and the presence of the cohesive periphyton mats, calcite has been observed along the cyanobacterial filaments.  Studies from riverine, lake, and marine stromatolite systems have indicated that the EPS matrix serves as the template for the precipitation of calcite.  We are performing detailed biochemical characterization of the polymers within specific periphyton mats to the point of being able to predict their role (or lack thereof) in biofilm structure/function, especially as related to calcification and/or sequestering of ionic species (notably calcium).

 Sponsor : South Florida Water Management District
 Links:  http://www.sfwmd.gov

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