Nutrients, Ecosystems, and the Evolving Detectability of Earth’s Biosphere
When: October 10, 2017 3PM PDT
The chemistry of Earth’s atmosphere has changed dramatically over time, and this evolution has been inextricably linked with innovations in biological metabolism and ecosystem complexity. A prominent example is the evolution of Earth’s oxygen cycle – the accumulation of significant quantities of O2 in the ocean-atmosphere system has completely reshaped electron flow through Earth’s surface environments, and provides a conspicuous remotely detectable signal of a pervasive biosphere. The oxygen cycle is in turn governed by feedbacks linking it with the carbon and sulfur cycles, the cycling of major and trace nutrients, and the exchange of volatiles with Earth’s interior. This talk will explore the apparently protracted oxygenation of Earth’s ocean-atmosphere system subsequent to the emergence of oxygenic photosynthesis, with an eye toward the roles of nutrient cycling and ecosystem structure in regulating atmospheric chemistry. The implications of these results will then be discussed in the broader context of evolving climate stability and the emergence and maintenance of atmospheric biosignatures on Earth-like planets.