CHARACTERIZATION OF MICROBIAL COMMUNITIES IN THE BIOLUMINESCENT BAYS OF VIEQUES, PUERTO RICO

Bioluminescent bays are spectacular wonders of nature and some of the brightest bays are found along the southern coast of the Puerto Rican island Vieques. The glow in these bays originates from an abundance of the planktonic dinoflagellate Pyrodinium bahamense var. bahamense, which releases light when it is agitated. This study is part of a larger research effort to understand the present and past environmental conditions that support these thriving bioluminescent ecosystems. Bay water residence times and current velocities will be used to quantify the modern relationship between dinoflagellate populations and the hydrodyamic regime. Since many of the important nutrient cycles are largely controlled by microbial degradation of organic matter in both bay water and shallow sediments, it is likely that sediment microbial ecology also has an impact on Pyrodinium populations in these bays. Examining the distribution of microbial populations in the sediment column may indicate which metabolic pathways are most influential in organic matter degradation.

In a typical marine sediment geochemical profile, [SO4]^2- decreases and DIC (dissolved inorganic carbon) increases with depth. This profile is explained by sulfate reduction(2CH₂O + SO₄^2- → H₂S + HCO^3-). Deep sites within the bays (>3 meters) follow this pattern, while shallow sites suggest more permeability, likely due to bioturbation, as the pore water sulfate and DIC concentrations do not change significantly throughout the core. It is assumed that the sediments are dominated by sulfate-reducing bacterial.(SRB) This study focuses on the microbial activity (using oligonuceotide probes for eukarya, archaea and bacteria) that occurs at sediment faces changes indicated by TOC (total organic carbon) and TIC (total inorganic carbon) in the sediment column at approximate 5, 10 and 15cm depth. DNA sequencing, T-RFLP (terminal-restriction fragment length polymorphism) analyses and FISH (fluorescent in-situ hybridization) imaging will be used to characterize the microbial populations and to gain an understanding of how those populations change with respect to sediment and pore water chemistry.