Disturbance of an impaired system

1. The influence of climate-induced alterations in dissolved organic matter on metal toxicity and UV radiation in Rocky Mountain streams William H. Clements, Dept. of Fishery and Wildlife Biology Jill S. Baron, Natural Resource Ecology Laboratory Colorado State University, Fort Collins, CO Diane M. McKnight, Institute of Arctic and Alpine Research University of Colorado, Boulder, CO Joseph S. Meyer, Department of Zoology and Physiology University of Wyoming, Laramie, WY

2. Compound Perturbations & Ecological Surprises Hypothetical recovery trajectory Two disturbance events Disturbance of an impaired system Paine et al. 1998

3. Heavy Metal Pollution UV Radiation Climate Change

4. Climate-induced changes in hydrology and biogeochemistry UV-b Radiation Quality & quantity of DOM • Fulvic Acid • Humic Acid • Humin Toxicity & bioavailability of metals Penetration of UV-b radiation Structure and function of benthic communities

5. Field Monitoring Spatiotemporal variation in physicochemical characteristics of 21 Colorado streams along a gradient of metal contamination Assess the relationship between discharge and DOC quality/quantity Characterize the influence of DOC on UV-b attenuation Measure effects of photobleaching on DOC quality/quantity

6. Field Monitoring

7. April-October, 2003 Routine phys-chem Discharge DOC Nutrients Cations, anions Heavy metals

8. Approx. Criterion Value

10. R2 = 0.29

11. R2 = 0.59 Prusha and Clements (2004)

12. Terrestrial Vegetation Discharge DOC Zn Zn Zn Zn Zn Zn

13. Vertical attenuation coefficients (Kd) Where: z = depth Ez = irradiance at depth E0 = irradiance at surface Kd = vertical attenuation coefficient

14. DOC and UV-b Attenuation 10 y = 4.39x-1.78 R2 = 0.8898 8 6 UV-B Attenuation (Kd) 4 2 Zuellig & Brooks, unpublished 0 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 Mean Summer [DOC] mg/L

15. Spatiotemporal variation in DOM quality Fractionation (XAD-8 resin) to determine quantity of fulvic acids 2-D fluorescence (Fluorescence Index) to determined source (ie., allochthonous vs. autochthonous

16. DOM Composition Microbial Origin Terrestrial Origin Appel & McKnight, unpublished

17. Photobleaching DOM Concentrated with RO Irradiated with Solar Simulator

18. X ~ 13.4% reduction Brooks et al., unpublished

19. Microcosm Experiments Assess effects of UV radiation and metals on benthic communities with different metal exposure histories Hypotheses: Effects of UV-B radiation + metals will be greater than either stressor alone Effects of metals will be greater on naïve communities (ie., no prior metal exposure)

20. West Tennessee Creek (reference) Arkansas River

21. Trays colonized in field Transferred to microcosms 2 x 2 factorial (metals x UV) for 10 d

22. Trays Drift net Stream flow UV-b Lamps Measured drift, metabolism, community structure

23. Macroinvertebrate Drift Kashian & Clements, unpublished

24. Community Metabolism Kashian & Clements, unpublished

25. Field Experiments Hypothesis: Benthic communities from metal-polluted streams are more susceptible to ambient UV-b radiation than those from unpolluted streams

26. Study Design • 12 sites • Split plot: UV-B excluded and ambient • 60-day duration (July-September) • Estimated UV-B exposure at stream bed • Chlorophyll a and community structure

27. ~ 2.5 tons cinderblock ~ 1000 feet PVC ~7500 miles UV-b No UV-b

29. UV-b Dosimeters

30. UV-B Quantification • Dosimeters replaced every 4 to 6 days • Absorbance calibrated to UV-B exposure • Measured depth, DOC, and Kd • Estimated total UV-B exposure at streambed

31. UV-B at the streambed Zuellig et al. unpublished

32. ANOVASig. Treat 0.047 Metals 0.937 Treat*Metals 0.991 0.25 0.20 Power Analysis Treat 0.516 Metals 0.074 Treat*Metals 0.056 0.15 Chlorophyll a ug/ L/cm2 Mean TChla(ugcm2) 0.10 0.05 NoUV UV 0 Background Low Med High Metals Gradient

33. 120 ANOVASig. Treat 0.832 Metals 0.001 Treat*Metals 0.640 100 80 Power Analysis Treat 0.110 Metals 1.00 Treat*Metals 0.412 Scraper Abundance 60 Mean Scrabund 40 20 NoUV UV 0 Background Low Med High Metals Gradient

35. 1.6 No UV 1.4 UV 1.2 1.0 Net Community Metabolism 0.8 0.6 0.4 0.2 0 W Tenn 4-mile Mosquito Chalk French Kashian et al. unpublished

36. Summary- Monitoring Results • DOC increased with discharge & vegetation • DOC strongly influenced UV-B attenuation • Spatial and temporal variation in DOC quality • Photobleaching reduced [DOC]

37. Summary- Microcosm Experiments • Metal effects greater on communities with no history of metal exposure • Drift in reference communities responded to UV-b and metals • Effects of metals & UV-b greater than either stressor alone

38. Summary- Field Experiments • Chlorophyll a increased when UV was eliminated at reference sites • Macroinvertebrate response to UV was weak  low statistical power • Community metabolism responded to both metals and UV-b

39. Implications • Benthic communities in shallow, alpine streams exposed to intense UV-b • Climate-induced changes in DOC are likely to increase UV-b exposure & metal bioavailability • Potential for interaction between metals and UV-b in structuring benthic communities

40. Future Research • Model relationship between climate change, stream hydrology and DOC • Photodegradation of DOC and metal bioavailability • Larger scale experiments to address statistical power

41. R829640 Acknowledgements Bob Zuellig, Donna Kashian, Marjorie Brooks Oliver Cox, Walter Johnston, Lea Ann Zuellig, Jeremiah Davis, Bryn Johnson, Dan Kashian, Cindy Kipley, Heather Lyons, Katy Mitchell, Jeremy Monroe, Joe Nicholson, Lorie Peterson, Blair Prusha, Travis Schmidt, Ted Soileau, Richard Thorp, Crystal Van Cutsem, Nicole Vieira, Rudy Zuellig Sr., Colorado Mountain College, Bureau of Land Management, Arapahoe National Forest, Pike National Forest, San Isabel National Forest, B + B Mines, Clear Creek County, Milam Family, Edith Seppi, Sondra Dirks