Life on an oxidizing planet: Microbial ecosystems of a Neoarchean carbonate platform

University Of Cincinnati Main Campus, Cincinnati OH

Investigators

Abstract

The story of life on Earth is largely the story of microbes and microbial ecosystems. Microbes were the first life on Earth, they are still the most abundant form of life, and it is becoming increasingly well understood that no complex life forms could survive without them. However, though the importance of microbes is undeniable, their early evolutionary history is not well understood. About 2.4 to 2.3 billion years ago, microbes changed this planet in a profound way by adding oxygen to the atmosphere. We do not know exactly how this oxygenation took place or how it impacted life on Earth, but we do know it ultimately paved the way for the evolution of multicellular life including all animals, plants, and fungi. This project will study fossilized microbial ecosystems that lived 2.5 billion years ago and will not only expand our knowledge about the early evolution of life on Earth, it will aid in the search for life on other planets. International collaboration, student training and educational outreach activities will be important components of the project. The microbial ecosystems that will be studied in this project are preserved across the Campbellrand-Malmani carbonate platform (CMCP) in South Africa. The CMCP formed over a 200 million year period, between 2.7 and 2.5 billion years ago. The project team will analyze the diverse microbial ecosystems that existed across the CMCP and produce a holistic view of a Neoarchean marine ecosystem and important details about a pivotal period in the coevolution of Earth and life. This will be accomplished by describing the preserved microfossils, using stable carbon isotope analysis to constrain the possible metabolic pathways the fossilized microorganisms used in life, calculating the diversity of observed microfossil assemblages and the similarity of CMCP microfossil assemblages observed in different microbialites, and evaluating evidence of Neoarchean biomineralization seen during preliminary observation. This project will use multiple microscopic and spectroscopic techniques, including transmitted light microscopy, secondary electron microscopy, transmission electron microscopy, confocal laser scanning microscopy, Raman spectroscopy, energy dispersive x-ray spectroscopy, isotope ratio mass spectrometry, and secondary ion mass spectrometry. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.