Sarah Ellen Johnston


Research Collaborations

Human activities are rapidly changing aquatic environments globally. In northern high latitudes warming temperatures, thawing permafrost, human development, and longer ice-free seasons impact the flow of materials from the terrestrial to aquatic environment. My research focuses on how biogeochemical cycles, particularly the carbon cycle, respond to these changes to understand the flow and composition of organic matter across the aquatic continuum. This research theme pairs field observations from streams and lakes across Interior Alaska with laboratory analyses including dissolved organic carbon analyses, absorbance and fluorescence spectroscopy, ultrahigh-resolution mass spectrometry (Orbitrap and FT-ICR MS), and lignin biomarker analyses to evaluate how organic matter composition influences the reactivity and fate of carbon in these changing aquatic environments.

Selected Publications

  1. Johnston, S. E., Gunawardana, P. V. S. L., Rood, S. B., & Bogard, M. J. (2022). Multidecadal Trends in Organic Carbon Flux Through a Grassland River Network Shaped by Human Controls and Climatic Cycles. Geophysical Research Letters, 49(4), e2021GL096885.
  2. Johnston, S. E., Carey, J. C., Kellerman, A., Podgorski, D. C., Gewirtzman, J., & Spencer, R. G. M. (2021). Controls on Riverine Dissolved Organic Matter Composition Across an Arctic-Boreal Latitudinal Gradient. Journal of Geophysical Research: Biogeosciences, 126(9), e2020JG005988.
  3. Johnston, S. E., Striegl, R. G., Bogard, M. J., Dornblaser, M. M., Butman, D. E., Kellerman, A. M., et al. (2020). Hydrologic connectivity determines dissolved organic matter biogeochemistry in northern high‐latitude lakes. Limnology and Oceanography, lno.11417.
  4. Johnston, S. E., Shorina, N., Bulygina, E., Vorobjeva, T., Chupakova, A., Klimov, S. I., et al. (2018). Flux and Seasonality of Dissolved Organic Matter From the Northern Dvina (Severnaya Dvina) River, Russia. Journal of Geophysical Research: Biogeosciences, 123(3), 1041–1056.


  • B.S. 2012, University of Tennessee at Chattanooga (Environmental Geology)
  • M.S. 2015, North Carolina State University (Earth Sciences)
  • Ph.D. 2019, Florida State University (Chemical Oceanography)
  • Postdoc 2019, University of Lethbridge (NSF Earth Sciences Postdoctoral Fellow)


Phone: 907-474-5231



Department of Chemistry & Biochemistry

University of Alaska Fairbanks

1930 Yukon Dr Room 180

Fairbanks, AK 99775-6160