Dr Karsh is a marine biogeochemist and postdoctoral researcher at ACE. She received her PhD in marine biogeochemistry through a joint program between Princeton University and the University of Tasmania.
Kristen studies cellular-scale processes that influence the local, regional, and global environment. Her research background lies in using stable isotopes to study the marine nitrogen cycle, and in studying how marine phytoplankton generate the stable isotope signals we observe.
Dr Karsh’s research focuses on marine phytoplankton, the microscopic plants of the ocean that form the base of the ocean food web, produce much of the air we breathe, and take up much of the carbon dioxide we produce.
The growth of phytoplankton is strongly influenced by changes in ocean chemistry and physics. The polar ocean is warming, freshening, becoming more acidic, and undergoing changes in iron bioavailability. Dr Karsh simulates these changes in the laboratory and measure their effects on phytoplankton. For example, we know that as ocean temperature warms, phytoplankton grow faster up to a point, beyond which growth abruptly declines and ultimately ceases.
The goal of her work with the ACE CRC is to identify the tipping point for key Southern Ocean phytoplankton species, under both iron-replete and iron-limited conditions.