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Project Progress

Little Salt Spring

A Proterozoic-analog microbial ecosystem was discovered at Little Salt Spring (FL) in 2011 and has unique potential to help us understand biosignatures of earth evolution, specifically the long delay in the continued oxidation of the surface earth after the initial rise at the Great Oxidation Event (GOE, ~2.4 Ga). The sinkhole is weakly stratified and has low concentrations of oxygen, sulfide and sulfate throughout the water column, similar to the geochemistry hypothesized for Proterozoic oceans. The sinkhole hosts a mixed oxygenic/anoxygenic community of microbial phototrophs. This site thus provides an opportunity to investigate biogeochemical and microbial processes in a Proterozoic ocean analog, including the ecological and geochemical controls on oxygen production and organic matter preservation. In addition, the microbial ecosystem at the site produces large quantitites of hopanoids, an important class of organic biomarkers that can be preserved in rocks for billions of years.

A second major field campaign in early Nov. 2014 was spearheaded by Macalady’s group in collaboration with two scientists from the Max Planck Institute for Marine Microbiology in Bremen, Germany, and two European scientific and technical divers from the Hydra Institute who are experts in the underwater deployment of microsensors. Microsensor measurements were carried out both for in situ microbial mats and mat samples maintained in the field lab at the site. These data are currently being used as input to a redox and oxygen budget for the mat ecosystem.