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

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... of nitrogen deposition across the Rockies. Southern Rockies-Colorado Front Range ... Central Rockies-Beartooth Mountains. Colorado lakes. Relative frequencies ... – PowerPoint PPT presentation

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


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
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7
Southern Rockies-Colorado Front Range
Lake Louise
Wolfe et al. 2001
8
Central Rockies-Beartooth Mountains
0
40
60
20
20
0
20
0
Saros et al. 2003
9
Central Rockies-Beartooth Mountains
Emerald Lake, Wyoming (2970 m. a.s.l.)
relative abundance
10
Relative frequencies ()
Colorado lakes
11
Observations experiments in Beartooth Mountain
lakes
  • 1) Resource physiology for N, P, and Si
  • 2) Vertical profiling in multiple lakes
  • 3) Nutrient enrichment experiments

12
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

13
Design of resource bioassays
Level of limiting nutrient added (?M) Level of limiting nutrient added (?M) Level of limiting nutrient added (?M) Level of limiting nutrient added (?M) Level of limiting nutrient added (?M) Excess
Si 3 5 10 25 150 NP
P 0 0.05 0.10 0.25 5.0 SiN
N 0.05 0.1 1.0 5.0 18 SiP
14
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15
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16
Half-saturation constants for growth (?M)
17
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 (CN, CP, NP, SiP,
    SiN), chlorophyll
  • Species composition

18
Spearmans rank correlation coefficient
19
How do these two species respond to nutrient
additions?
  • Nutrient enrichment experiments
  • Beartooth Lake- July 2002
  • Control, P, N, NP
  • Beauty Lake- July 2003
  • Control, high NP, low NP, high SiP, low SiP
  • Lake water was filtered through 150 ?m mesh and
    incubated at 3 m
  • When added N18 ?M, P5 ?M, Si100 ?M

20
Initial nutrient conditions
21
ANOVA plt0.0001 Tukey HSD controlN
p0.001 controlNP plt0.0001
ANOVA p0.001 Tukey HSD controlN
p0.039 controlNP p0.015
22
Experiment in Beauty Lake-2003
ANOVA plt0.0001 Tukey HSD controlhigh NP
plt0.0001 controllow NP p0.039 high
to low NP p0.10
23
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

24
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

25
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

26
Overview
Speaker Indicator Critical N load (kg N/ha/yr)
Bowman Alpine plant communities Individual plants 4 Community 10 Nitrate leaching gt20
Allen Exotic grasses in the desert Coastal sage communities 5 60
Saros Diatom communities in alpine lakes 1.5 (Baron 2006)
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