HR: 0800h
AN: B41A-0028    [Abstracts]
TI: Microbe-Sediment Interactions Controlling Growth of Modern Marine Stromatolites: Highborne Cay, Bahamas
AU: * Bowlin, E M
EM: ebowlin@rsmas.miami.edu
AF: University of Miami Rosenstiel School of Marine & Atmospheric Science Marine Geology & Geophysics, 4600 Rickenbacker Causeway, Coral Gables, FL 33149, United States
AU: Reid, R P
EM: preid@rsmas.miami.edu
AF: University of Miami Rosenstiel School of Marine & Atmospheric Science Marine Geology & Geophysics, 4600 Rickenbacker Causeway, Coral Gables, FL 33149, United States
AU: Gaspar, A P
EM: agaspar@rsmas.miami.edu
AF: University of Miami Rosenstiel School of Marine & Atmospheric Science Marine Geology & Geophysics, 4600 Rickenbacker Causeway, Coral Gables, FL 33149, United States
AB: Modern stromatolites forming in seawater of normal marine salinity along the margins of Exuma Sound, Bahamas, provide an ideal opportunity to document interactions between microbial mat communities and the environment that lead to stromatolite growth. The well-laminated and easily accessible stromatolite build-ups at Highborne Cay (76^o49' W, 24^o43' N) form in the back-reef of a 2.5km algal-ridge fringing reef complex along the eastern shoreline (facing Exuma Sound) of the island. The stromatolites form as ridges and columnar heads in the shallow subtidal zone. The mat communities on the surface of the stromatolites include both prokaryotic and eukaryotic organisms. The prokaryotic mats are dominated by gliding filamentous cyanobacteria and are found chiefly on the low-lying, shallow stromatolite ridges. In contrast, the mixed eukaryotic-prokaryotic mat communities are predominantly observed on columnar head stromatolites and are composed of diatoms overlying filamentous cyanobacteria. Tube diatom mats are dominant in winter and spring, whereas stalked diatoms are dominant in summer and fall. The mixed eukaryotic-prokaryotic communities accrete sediment more rapidly than the purely prokaryotic mats, with diatoms trapping sediment, which is subsequently bound by the upward migration of the underlying filamentous cyanobacteria. A major control on the distribution of microbial communities on Highborne Cay stromatolites is the migration of sand waves, both intertidal and subtidal, across the stromatolite reef. These migrating sand waves bury and expose the reef episodically for periods of days, weeks, and months. Variations in the duration of these sedimentation events reflect changes in physical energy along the reef, which when coupled with seasonality, control microbial growth and resultant stromatolite formation.
DE: 3022 Marine sediments: processes and transport
DE: 4840 Microbiology and microbial ecology (0465)
SC: Biogeosciences [B]
MN: 2007 Fall Meeting