1. DISSOLVED ORGANIC MATTER AND NITROGEN REDOX CHEMISTRY IN AQUATIC ALPINE ECOSYSTEMS Matt Miller Ph.D. Student Advisor: Diane McKnight

2. Biogeochemical Hot Spots and Hot Moments Hot Spot: An area exhibiting high rates of biogeochemical transformation in comparison to the surrounding environment Hot Moment: Short periods of time during which reactions rates are higher than those during the rest of the season McClain et al. (2003)

3. O lignin MeO O lignin OH OMe OH O lignin MeO O lignin OH OMe OH HO O O Me Slide by: Rose Cory

4. Fe 3+ Fe 2+ NO 3 - NO 2 - + DOM  DOM-N Humics act as electron shuttle Ferrous Wheel Hypothesis CO 2 Acetate Oxidized DOM DOM reducing microorganism Reduced DOM e-e- DOM: Electron Transfer Slide by: Chris Jaros

5. Green Lakes Valley ALBION TOWNSITE LAKE ALBION GL4 GL5 NAVAJO STREAM NIWOT RIDGE

6. Question 1: Is the stream in the upper reaches of the catchment acting as a hotspot for C as well as N? Question 2: Do lakes in headwater ecosystems act as hotspots? If so, is the importance of lake processing a function of seasonal changes in hydrology and/or biology? Research Questions

7. *Tracer Injection w/ LiBr *Modeled with OTIS *Sampled for: -DOC -N species -Li and Br Stream as Biogeochemical Hot Spot Miller et al. (2006)

8. Main Channel: Storage Zone: Advection Dispersion Lateral inflow Transient storage Decay Modeling Hyporheic Exchange: OTIS

9. Solute Transport Modeling Results Miller et al. (2006)

10. Stream Decay (λ) Storage Zone Decay (λ s ) NO 3 - -1.0 x 10 -3 1.0 x 10 -4 NH 4 + 1.2 x 10 -3 -7.9 x 10 -5 DOC1.6 x 10 -2 -1.3 x 10 -4 Redox Index6.5 x 10 -3 -8.4 x 10 -5 λCλC λsCλsC Reactive Transport Results

11. Hydrologic Controls on DOM Hood et al. (2003)

12. Alpine: Green Lake 4 (GL4) Subalpine: Lake Albion (ALB)

13. GL4 (Alpine) ALB (Subalpine) Response to Hydrologic Change Response to Biological Change

14. Humic Redox Results GL4 (Alpine) ALB (Subalpine) Response to Biological Change

15. Lake Modeling There is clearly a large signal due to both hydrologic and biologic changes in the system. Modeling Approach: Mass Balance for a Lake with a Well Mixed Epilimnion (both GL4 and ALB)

16. Proposed Mass Balance Calculations Conservative Transport: Reactive Transport (1 st order rxn. at steady-state): Variables to be modeled: DOC, NO 3 -, NH 4 +, FI, PARAFAC 1 st Order Rxn.? k(?): DOC, chlorophyll a, temperature, pH, etc?