Roberts, B. J.. Cornell University, bjr11@cornell.edu
Ostrom, N. J.. Michigan State University, OstromN@pilot.msu.edu
Howarth, R. W.. Cornell University, rwh2@cornell.edu
Bergsma, T. T.. Kellogg Biological Station and Michigan State University, BergsmaT@pilot.msu.edu

 
ARE RESPIRATION RATES EQUAL OVER DIEL CYCLES IN AQUATIC ECOSYSTEMS?: A NEW METHOD AND APPLICATION USING NATURAL ABUNDANCE OXYGEN ISOTOPES
 
The majority of methods employed to measure ecosystem metabolism are based upon the assumption that respiration rates during the day are equal to those measured at night. If respiration rates are found not to be constant over diel cycles, our understanding of the magnitude of gross primary production in aquatic ecosystems might be greatly altered. By measuring oxygen isotope ratios in situ, the relative contributions of photosynthesis, respiration, and atmospheric exchange to O2 flux can be partitioned for each time period. In this study, we present a new approach of using oxygen isotopes to measure ecosystem metabolism. The method involves the isotopic analysis of O2 and N2 by dynamic flow using a gas chromatograph/isotope ratio mass spectrometer technique as well as the measurement of O2:N2:Ar gas ratios via dual inlet mass spectrometry. Analytical precision for lab and field samples was better than 0.3 per mil for oxygen isotopic composition of dissolved O2. Data will be presented from both experimental freshwater ponds and marine mesocosms.
 
Day: Tuesday, Feb. 2
Time: Poster
Location: Sweeney Center
 
Code: SS32TU0982S