Moving from correlation to mechanism: testing the role of temperature and oxygen change in the Great Ordovician Biodiversification Event

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Oxygen levels and temperature change are generally recognized as two of the most important environmental factors affecting marine ecosystems, both in the geologic past and in the modern ocean. This project examines the Great Ordovician Biodiversification Event (GOBE), a major increase in the diversity of marine life that occurred approximately 460 million years ago, when there were dramatic changes in oxygen levels and temperature. This project will use a unique combination of geological fieldwork, laboratory measurements of trace metal isotopes, Earth system modeling, and physiological insights from living organisms to understand the role that both oxygen and temperature play in driving major events in the history of life, such as evolutionary radiations and mass extinctions. The results also will help stakeholders better predict how modern global change will affect living marine populations, with implications for the future development of economic and food resources (e.g., fishing and aquaculture). This project will use an ecophysiological approach to test the causal role of oxygen and temperature change in driving biodiversity dynamics during the Great Ordovician Biodiversification Event. This integrated project will 1) build a record of Ordovician oceanic redox change using new Mo and U trace metal isotope measurements, and compile temperature estimates from the literature, 2) conduct the necessary physiological measurements on brachiopods, bryozoans, mollusks, and echinoderms that are required to fully leverage the Metabolic Index in addressing paleontological questions, 3) use Earth system models to build a time series of model states consistent with available geochemical data, and 4) use the Metabolic Index to evaluate the proportion of biotic change observed in the fossil record during the GOBE that can be explained by oxygen, temperature, and their synergistic combination. The use of physiological measurements to understand how ecosystem reorganizations can be mediated at the organismal scale creates mechanistic links that complement the descriptive and correlative methods for testing hypotheses of climate-ecosystem linkages. Broader Impacts of this proposal include early career training, ecological conservation, and a STEM outreach project with local high school robotics teams.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.