2007-2008 Schlanger Fellow – Heather Schrum

Heather Schrum

University of Rhode Island

Quantification of Low Rates of Metabolic Activity in the Deep Subseafloor Using Sulfate Oxygen Isotopic Compositions





fellow-schrumThe purpose of this study is to develop a unique way to quantify low metabolic rates, which is essential for constraining the environmental limits on life. I propose to test hypotheses related to sulfate metabolism and to develop a method that will quantify low rates of sulfate reduction and potentially iron reduction in low activity subseafloor environments. The sulfate reduction method relies on the oxygen isotope composition of dissolved pore fluid sulfate, δ18OSO4. Iron reduction rates are calculated from sulfate reduction rates, total carbon and alkalinity (Wang, G., 2006. URI Ph.D. dissertation). Because the sulfate and iron reduction rates are well constrained at Leg 201 Site 1226 (Wang, 2006), I will use these data to examine systematic relationships between oxygen isotope exchange and sulfate reduction rates. I will apply the results to a low activity site, Site 1225, to infer sulfate and/or iron reduction rates.




After spending my childhood exploring the coast of Connecticut, I headed to upstate New York to study geology at Hamilton College. Although deprived of the coast throughout most of the academic year, I was exposed to life at sea as a participant in the U.S. Antarctic Program in 2004 and 2005, when I studied climate change and its influence on the Larsen Ice Shelf. Luckily, my time at sea did not end there. As a second year Ph.D. student at the University of Rhode Island’s Graduate School of Oceanography, I recently spent two months in the South Pacific studying interstitial seawater chemistry under the guidance of Arthur Spivack and Steven D’Hondt. When I’m not not focusing on science, I enjoy instructing yoga and fishing with my fiancée.