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Diatom shifts in alpine lakes of the southern and central Rocky Mountains

Diatom shifts in alpine lakes of the southern and central Rocky Mountains. Jasmine E. Saros University of Wisconsin-La Crosse. Collaborators. Alexander P. Wolfe, University of Alberta, Canada Sebastian J. Interlandi, Drexel University Tamara Blett, National Park Service

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Diatom shifts in alpine lakes of the southern and central Rocky Mountains

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  1. Diatom shifts in alpine lakes of the southern and central Rocky Mountains Jasmine E. Saros University of Wisconsin-La Crosse

  2. Collaborators Alexander P. Wolfe, University of Alberta, Canada Sebastian J. Interlandi, Drexel University Tamara Blett, National Park Service Jill Baron, Colorado State University Craig Williamson, Miami University Lisa Graumlich, Montana State University Jeffrey Stone, University of Nebraska

  3. Sensitivity of diatoms • Often the first aquatic organisms to respond to environmental changes • Change in species assemblages, chemical composition • Changes are well-documented in response to nutrients, pH, climate

  4. Beartooths Front Range

  5. Enhanced atmospheric N deposition • Major effects of nitrogen deposition on aquatic systems: • Fertilization: adding biologically-available nitrogen • Acidification: one component of acid precipitation • Alpine lakes may be more sensitive than temperate lakes to nitrogen deposition • The growth of algae in these lakes is often limited by nitrogen • These lakes have low buffering capacities • Spatial variation in rate of nitrogen deposition across the Rockies

  6. 1970 1950 1900 Southern Rockies-Colorado Front Range Lake Louise Wolfe et al. 2001

  7. Central Rockies-Beartooth Mountains 0 20 40 60 0 20 0 20 Saros et al. 2003

  8. Central Rockies-Beartooth Mountains Emerald Lake, Wyoming (2970 m. a.s.l.) % relative abundance

  9. Relative frequencies (%) Colorado lakes

  10. Observations & experiments in Beartooth Mountain lakes 1) Resource physiology for N, P, and Si 2) Vertical profiling in multiple lakes 3) Nutrient enrichment experiments

  11. What are the resource requirements of these two diatom taxa? Resource physiology experiments • Determined requirements for N, P, and Si • Used lake water from Beartooths with low initial nutrient concentrations • Collected cells from lakes in the area • Incubated in Beauty Lake

  12. Design of resource bioassays

  13. F. crotonensis S. pinnata  (day-1) T. glans A. formosa

  14. Half-saturation constants for growth (M)

  15. What are their distribution patterns in relation to physicochemical parameters? Vertical profiles • Sampled 7 lakes • Every 3 m: • Temperature, pH, conductivity, PAR, SRP, nitrate, silica, seston ratios (C:N, C:P, N:P, Si:P, Si:N), chlorophyll • Species composition

  16. Spearman’s rank correlation coefficient

  17. How do these two species respond to nutrient additions? Nutrient enrichment experiments • Beartooth Lake- July 2002 • Control, P, N, N+P • Beauty Lake- July 2003 • Control, high N:P, low N:P, high Si:P, low Si:P • Lake water was filtered through 150 m mesh and incubated at 3 m • When added: N=18 M, P=5 M, Si=100 M

  18. Initial nutrient conditions

  19. ANOVA p<0.0001 Tukey HSD control:N p=0.001 control:N+P p<0.0001 ANOVA p=0.001 Tukey HSD control:N p=0.039 control:N+P p=0.015

  20. Experiment in Beauty Lake-2003 ANOVA p<0.0001 Tukey HSD control:high N:P p<0.0001 control:low N:P p=0.039 high to low N:P p=0.10

  21. Summary • Both species of diatoms have moderate N and very low P requirements • The recent increases in these two species across the western U.S. can be attributed to enhanced rates of N deposition • Future work should include: • Sediment cores from additional areas that vary in rates of N deposition • Culturing work to quantify the minimum N level at which phytoplankton communities shift

  22. Critical N load determination from diatoms • Current work: development of a critical N load model based on existing diatom records plus those of additional parks: • Sequoia • Glacier • Northern Cascades • Baron (2006) used diatom records to test her model • Determined a critical load of 1.5 kg N/ha/yr

  23. Acknowledgements • Funding: • National Science Foundation (DEB 0089600) • UW-L Faculty Research Grant • River Studies Center • Students: • David Dean, Shaina Doyle, Lisa Poser, Rita Seston, Courtney Smith, LeeAnne Thorson, Courtney Wigdahl, Kate Wroblewski • Assistance in the field and lab: • Misa Saros, Barbara Interlandi

  24. Overview

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