Extracellular
Polymeric Substances of Everglades Periphyton Mats: Role in Calcium
Carbonate Deposition
(Collaborators: Scot Hagerthey and Brent Bellinger) |
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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).
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