ABSTRACT

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).

Archean and Proterozoic oceans have no known analogues in modern aquatic environments, and their biogeochemistry and microbiology remain enigmatic. Lake Matano's physical structure, abundance of Fe and dearth of sulfate mirror the stratified ferruginous conditions thought to prevail in these early oceans. Preliminary results indicate proliferation of anoxygenic photoferrotrophs, and support the significance of these organisms for the primary production in the early ocean. The active methane cycle in Lake Matano demonstrates that methanogenesis and methanotrophy could have also been important components of the Earth?s early marine C cycle. The methane cycle appears coupled to the iron cycle through anaerobic oxidation of methane with Fe(III) as an electron acceptor, a novel biogeochemical pathway. Given that the deep waters of Lake Matano may be the best available modern analogue for the anoxic, ferrugenous, and organic-poor early waters, investigators seek to further elucidate the extent, mechanisms and the microbial communities responsible for these processes. The specific objectives of this project are:
1) to generate high resolution profiles of the geochemistry of iron, methane, and organic carbon in the deep waters and sediments of Lake Matano using field and laboratory measurements;
2) to characterize the water column stratification, hydrodynamics, and the rates of physical substance transport using direct measurements and modeling;
3) characterize the community structure and biogeochemical reactions associated with the microbial communities in the lake and investigate their metabolisms in pure and mixed cultures;
4) simulate the biogeochemical cycling of iron, carbon, and methane in the lake using reaction-transport models and calculate the in-situ reaction rates.

These results from Lake Matano, Indonesia, will provide the first glimpse at the microbial ecosystems that can develop in a stable, ferruginous aquatic environment. They can confirm the discoveries of two novel biogeochemical pathways.

Broader Impacts: Phylogenetic data will place extant organisms into an evolutionary framework. Generated reactive transport models will be transferable to biogeochemical processes in other tropical stratified lakes. These models and ecology data will help examine biogeochemical processes in paleo-environments. Physical data will help understand mixing in weakly stratified deep lacustrine and marine environments. Additionally, a novel internationalized educational plan will bring faculty and students from the USA and Indonesia together in the field and in the laboratory.

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