THE RELATIONSHIP BETWEEN NITROGEN FIXATION AND TEMPERATURE: WHAT CAN VARIOUS METHODS TELL US?
Nitrogen fixation rates should respond predictably to changes in temperature, with potential consequences for productivity and food web dynamics in N-limited ecosystems. Our objective was to estimate N2-fixation rates across a temperature gradient using both acetylene reduction assays and 15N2 addition in a controlled streamside channel experiment (n=3, treatment means = 6, 11, 16, 21, and 28 °C). N2-fixation rates were measured 3 times during biofilm assemblage development. There was a significant positive relationship between temperature and rates of acetylene reduction at 4 (R2=0.91, p=0.01), 6 (R2=0.81, p=0.04), and 8 weeks (R2=0.88, p=0.02), while no significant relationship was observed between temperature and direct measurement of N2-fixation via incorporation of 15N2 into N-fixer biomass. Results suggest that C2H2:N2-fixation ratios generally increased with temperature; however, explanations for this pattern and interpretation of estimates of N2-fixation rates gained using each method must be further explored. Advances in N2-fixation measurements are fundamental to our efforts to understand how this critical process contributes to nitrogen availability in ecosystems, as well as how N2-fixation rates are likely to respond to global climate change.
Goldschmidt, J. B., St. Catherine University, USA, firstname.lastname@example.org
Welter, J. R., St. Catherine University, USA, email@example.com
Ahles, A. M., St. Catherine University, USA, firstname.lastname@example.org
Williamson, T. J., Montana State University, USA, email@example.com
Time: 18:00 - 20:00
Location: Poster/Exhibit Hall
Presentation is given by student: Yes