How does feeding 7.5 billion people impact the ocean? Population growth, air pollution, and the oceanic CO2 sink
The Faculty of Science Research Committee presents:
A Faculty of Science Special Research Seminar
Dr. Katye Altieri, Department of Oceanography, UCT
Human activities have doubled the amount of reactive nitrogen (N) on Earth since the preindustrial era due to fossil fuel combustion and fertilizer production. There are significant detrimental impacts of this excess N on terrestrial and aquatic ecosystems, such as increased ozone, acidification, and eutrophication, though little is known about the impact on the remote ocean. Global models indicate that the human-derived N emissions that reach the ocean through atmospheric transport and deposition could have a large and direct impact on global climate change by fertilizing ocean biology and stimulating the oceanic carbon dioxide (CO2) sink. However, these global models are difficult to validate due to a lack of direct measurements in the marine environment. Here, I will present measurements from the subtropical North Atlantic Ocean showing that a significant amount of the nitrate deposited to the ocean from the atmosphere derives from pollution on land. In contrast, evidence will be presented that ammonium and organic N in atmospheric deposition derive primarily from surface ocean biological activity, which is contrary to all expectations and model predictions. This work suggests that the paradigm whereby the ocean is a passive recipient of anthropogenic N deposition requires re-examination, and that the impacts of atmospheric N pollution on ocean fertility, oceanic CO2removal, and nitrous oxide (N2O) emissions may currently be overestimated.
Dr. Katye Altieri is a Lecturer in the Department of Oceanography at the University of Cape Town researching climate and biogeochemistry in the marine atmosphere. Her research is focused on a number of topics, including surface ocean-lower atmosphere nitrogen cycling, the impact of air pollution on the ocean, and the chemical composition and climate impact of organic aerosols. Katye obtained her PhD in Oceanography from Rutgers University and a Masters in Public Policy from Princeton University. She was a NOAA Climate and Global Change Postdoctoral Fellow jointly appointed between Princeton and Brown University. In 2015, Katye was awarded an NRF P-rating, the highest accolade for a young scientist (see the video here).