Title: Diatom shifts in alpine lakes of the southern and central Rocky Mountains
1Diatom shifts in alpine lakes of the southern and
central Rocky Mountains
- Jasmine E. Saros
- University of Wisconsin-La Crosse
2Collaborators
- 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
-
3Sensitivity 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
4Beartooths
Front Range
5Enhanced 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
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7Southern Rockies-Colorado Front Range
Lake Louise
Wolfe et al. 2001
8Central Rockies-Beartooth Mountains
0
40
60
20
20
0
20
0
Saros et al. 2003
9Central Rockies-Beartooth Mountains
Emerald Lake, Wyoming (2970 m. a.s.l.)
relative abundance
10Relative frequencies ()
Colorado lakes
11Observations experiments in Beartooth Mountain
lakes
- 1) Resource physiology for N, P, and Si
- 2) Vertical profiling in multiple lakes
- 3) Nutrient enrichment experiments
12What 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
13Design 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
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16Half-saturation constants for growth (?M)
17What 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
18Spearmans rank correlation coefficient
19How 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
20Initial nutrient conditions
21ANOVA plt0.0001 Tukey HSD controlN
p0.001 controlNP plt0.0001
ANOVA p0.001 Tukey HSD controlN
p0.039 controlNP p0.015
22Experiment in Beauty Lake-2003
ANOVA plt0.0001 Tukey HSD controlhigh NP
plt0.0001 controllow NP p0.039 high
to low NP p0.10
23Summary
- 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
24Critical 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
25Acknowledgements
- 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
26Overview
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)