Research Themes

My work takes an O2-centric approach to understanding Earth's carbon cycle

How does cryptic oxygen cycling influence Earth's major biogeochemical cycles?

By "cryptic" oxygen cyling, I am referring to the production and consumption of O2 that occurs through short-lived, reactive compounds called reactive oxygen species (ROS). We often think of respiration and photosynthesis as the primary reactions that influence O2 concentrations. However, microbes can also consume O2 through reactions that make ROS such as superoxide (O2 with an extra electron) and hydrogen peroxide (H2O2). These ROS react with a many biologically important molecules in seawater, including important nutrients like organic carbon and metal cofactors. My work focuses on understanding the causes and effects of ROS production in the global ocean.

How much ROS do microorganisms make?

Reactive oxygen species production is widespead in the ocean. ROS such as superoxide and hydrogen peroxide are relatively short lived (~1 min for superoxide, ~hours-days for hydrogen peroxide), so quantifying ROS production and concentrations in the marine environment can be challenging. I combine lab-studies of ROS-producing microganisms, sea-going observations of ROS-production and concentrations in the marine water column, and computational models to try to understand how much ROS is produced in the ocean. I am also currently developing triple oxygen isotope and clumped oxygen isotope methods to fingerprint reactions involving ROS in the environment.

How does the biological oxygen cycle respond to environmental change?

The biological production, consumption, and recycling of oxygen in the surface ocean is influenced by a wide range of environmental factors, including tempature, pH, and nutrient availability. My work investigates how these environmental changes conspire to influence the marine oxygen cycle and water-column oxygen concentrations.