Conferences - Seminars

  Tuesday 21 March 2017 12:15 - 13:15 GR C0 01

EESS talk on "Ecosystem metabolism and carbon fluxes in a sub-alpine stream network"

By Dr Amber Ulseth, SBER
Short biography:
Amber J. Ulseth is currently a Scientist within the Stream Biofilm and Ecosystem Research (SBER) laboratory at EPFL. Her research has included studying the incorporation of anthropogenic nitrogen and carbon into urban stream food webs, the role of migratory fish on nitrogen cycling in Venezuelan streams, and dissolved organic carbon cycling in the Colorado River Basin, USA. Amber is currently working on ecosystem metabolism and carbon fluxes in streams of the Austrian and Swiss Alps. Prior to working at EPFL, Amber was a post-doctoral researcher with Prof. Dr. Tom Battin at the University of Vienna. Amber received her BS from the University of Minnesota-Duluth, her MS from the University of North Carolina Greensboro, and her PhD from the University of Wyoming.

Stream metabolism describes the amount of carbon produced and turned over at the ecosystem level. Both ecosystem respiration (ER) and gross primary production (GPP) are driven by a number of controlling variables, including water temperature and hydrology. Using continuous measurements of ecosystem metabolism, I will discuss the patterns and processes of ecosystem metabolism across the Ybbs River Network (YRN), a sub-alpine stream network located in the Austrian Alps. Temperature can drive metabolism, which was quantified as described by Arrhenius kinetics. Network-wide ER activation energy (AE) was 0.60 electron volts (eV), which was within the expected range for metabolism kinetics. However, network-wide AE for GPP was 1.8 to 2.4-fold greater (0.67 eV) than predicted based on metabolism kinetics alone. The variability in AE of ER and GPP within the network indicates that individual streams may respond differently to changing environmental conditions, such as changes in the timing and delivery of snowmelt. The winter of 2013/2014 was anomalously warm compared to the previous winter across the study catchment, resulting in a shift of winter precipitation from snow to rain. My findings when comparing ecosystem metabolism across the years, suggest that the YRN evolved from a transient sink to source of carbon dioxide (CO2) in spring as snowmelt hydrology differed following the high snow versus low snow winter.  This shift towards increased heterotrophy during spring snowmelt following a warm winter has potential consequences towards annual ecosystem metabolism, as spring GPP contributed on average 33% to annual GPP fluxes compared to spring ER, which averaged 21% of annual ER fluxes. We propose that Alpine headwaters shunt less organic carbon to downstream ecosystems, but will emit more within-stream respiratory CO2 to the atmosphere annually, as the climate gets warmer.

Organization EESS - IIE

Contact Prof. Tom Battin, SBER

Accessibility General public

Admittance Free

This event is internal