diatom shifts in alpine lakes of the southern and central rocky mountains
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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 - PowerPoint PPT PresentationTRANSCRIPT
Diatom shifts in alpine lakes of the southern and Diatom shifts in alpine lakes of the southern and central Rocky Mountainscentral Rocky Mountains
Jasmine E. SarosJasmine E. SarosUniversity of Wisconsin-La CrosseUniversity of Wisconsin-La Crosse
CollaboratorsCollaborators
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
Sensitivity of diatomsSensitivity 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
Beartooths
Front Range
Enhanced atmospheric N depositionEnhanced 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
Southern Rockies-Colorado Front Range
19701950
1900
Lake Louise
Wolfe et al. 2001
Fragilariacrotonensis
Cyclotella bodanicavar. lemanica
Aulacoseiradistans
Small Fragilariaspp.
Beartooth Lake, WYOMING (~2590 m)
0
10
20
30
40
depth (cm)
20 80 30 40relative frequencies
198919601905
Central Rockies-Beartooth Mountains
0 40 6020 200 200
Saros et al. 2003
Emerald Lake, Wyoming (2970 m. a.s.l.)
% relative abundance
Central Rockies-Beartooth Mountains
Colorado lakesRelative frequencies (%)
Observations & experiments in Observations & experiments in Beartooth Mountain lakesBeartooth Mountain lakes
1) Resource physiology for N, P, and Si
2) Vertical profiling in multiple lakes
3) Nutrient enrichment experiments
What are the resource requirements of these What are the resource requirements of these two diatom taxa?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
Design of resource bioassaysDesign of resource bioassays
Level of limiting nutrient added (M) Excess
Si 3 5 10 25 150 N&P
P 0 0.05 0.10 0.25 5.0 Si&N
N 0.05 0.1 1.0 5.0 18 Si&P
Silica (uM)
0 20 40 60 80 100 120 140 1600.0
0.2
0.4
0.6
0.8
(d
ay-1
)
F. crotonensis
S. pinnata
A. formosa
T. glans
Half-saturation constants for growth (Half-saturation constants for growth (M) M)
S. pinnata F.crotonensis A. formosa
N 0.003(0.056)
0.028(0.063)
0.041(0.038)
P 0.0003(0.005)
0.0008(0.065)
0.0009(0.003)
Si 3.82(1.09)
0.78(0.97)
3.35(3.38)
What are their distribution patterns in relation to What are their distribution patterns in relation to physicochemical parameters?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
Spearman’s rank correlation coefficientSpearman’s rank correlation coefficient
Fragilaria crotonensis Asterionella formosa
All lakes Beartooth All lakes Beartooth
Conductivity 0.46(0.0003)
0.35(0.10)
0.20(0.13)
0.31(0.14)
PAR 0.37(0.009)
0.54(0.007)
0.24(0.09)
0.44(0.03)
C:P 0.078(0.56)
0.71(0.0002)
0.44(0.0005)
0.44(0.04)
N:P 0.0059(0.97)
0.56(0.008)
0.43(0.001)
0.51(0.02)
Si:P 0.032(0.81)
0.71(0.0002)
0.48(0.0001)
0.41(0.05)
How do these two species respond to How do these two species respond to
nutrient additions?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
Dissolved nutrients(M)
Se stonratios(M)
Lake PO4 NO3 Si C:N C:P N:P Si:N Si:P
Beartooth 0.04 1.34 36.0 9.9 197 19.9 0.88 17.5
Beauty <0.015 1.43 29.7 10.8 323 30.0
Initial nutrient conditionsInitial nutrient conditions
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
Fragilaria crotonensis
Control
N + P
N
P
0
50
100
150
200
250
Cells/ml
Asterionella formosa
Control
P
N N+P
0
10
20
30
40
50
60
Cells/ml
Asterionella formosa
control
high N:P
low N:P
high Si:Plow Si:P
0
5
10
15
20
25
30
35
40
45
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
Experiment in Beauty Lake-2003
SummarySummary
• 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
Critical N load determination from diatomsCritical 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
• 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
AcknowledgementsAcknowledgements
OverviewOverview
Speaker Indicator Critical N load
(kg N/ha/yr)
Bowman Alpine plant communities Individual plants: 4
Community: 10
Nitrate leaching: >20
Allen Exotic grasses in the desert
Coastal sage communities
5
60
Saros Diatom communities in alpine lakes
1.5 (Baron 2006)