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Water transparency to UV radiation in montane lakes: consequences of climate-driven changes in terrestrial inputs. Presented by Craig Williamson at the "Perth II: Global Change and the World's Mountains" conference in Perth, Scotland in September 2010.
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Water transparency to UV radiation in montane lakes: consequences of climate-driven changes in terrestrial inputs.
Craig Williamson, Carrie Kissman, Kevin Rose
Miami University Global Change Limnology Lab
Jasmine Saros
University of Maine Climate Change Institute
Janet Fischer & Jennifer Everhart
Franklin & Marshall College
Responses to Climate Change: Where to sample?
Lakes as Sentinels & Integrators of Climate Change
Williamson et al. 2009 Limnol. Oceanogr. 54:2273
Harsch et al. 2009. Ecology Letters 12:1040.
Treeline is advancing to higher elevations (black dots) in 52% of 166 systems sampled worldwide.
Receding treelines observed in only 1% of systems.
DOM Source is Largely Terrestrial
Low – Medium - High
Terrestrial Vegetation
DOM in water
DOM as an Ecosystem Regulator
Low DOM
High transparency
High DOM
Low transparency
DOM Regulates
UV transparency
Compensation depth
Mixing depth
Nutrient cycling
Anoxia
Metal toxicity
Pesticide toxicity
Other …
DOM Has Doubled in 15-20 yr in Many Lakes & Rivers
Evans et al. 2006. Global Change Biology 12:2044 (See also Findlay 2005. FEE 3:133; Monteith et al. 2007. Nature 450:537)
Beartooth Mountains, MT-WY, USA
Saros et al. 2005 CJFAS 62:1681
Ganguly et al. 2009. Proc. Nat. Acad. Sci. U.S. 106:15555
Central Rocky Mountains, Western USA: Changing Snowfall in Red Lodge, MT
Rose et al. 2009 Photochem. Photobiol. Sci. 8:1244
Changes in Diatoms in the Central Rocky Mtns. Associated with Climate Change
Saros et al. 2003. AAAR 35:18
Central Question:
How will climate-driven increases in DOM influence consumer:producer relationships
in mountain lakes?
Heterotrophic Consumers
Zooplankton (H)
Autotrophic
Phyto. (A)
Climate Change in Montane Ecosystemstemperature, precipitation, treeline --> more DOM
?
HB:AB = 3
(H)
(A)
(H)
(A)
EpilimnionWarm, High Light
HypolimnionCold, Dark
?
?
?
?
(H)
(A)
(H)
(A)
EpilimnionWarm, High Light
HypolimnionCold, Dark
Anoxic
(H)
(A)
(H)
(A)
EpilimnionWarm, High Light
HypolimnionCold, Dark
?
?
?
Experimental Design
(H)
(A) ?
(H)
(A) ?
With DOM
Resource Subsidy
No DOM
Resource Subsidy
(H)
(A) ?
(H)
(A) ?
1.5 m
8.0 m
+/- Zooplankton
Experimental Design
• 3 week field microcosms
• 3.8 L transparent bags
• Natural phytoplankton
• Treatments (3 replicates):
+/- Zooplankton grazers
+/- DOM
2 depths to give different light & temperature: – 1.5 m (epilimnion)
– 8 m (hypolimnion)
Phytoplankton Biomass
Treatment
Initi
al
- DO
M
+ D
OM
- D
OM
+ D
OM
- DO
M
+ D
OM
- D
OM
+ D
OM
Bio
ma
ss
(µ
g L
-1)
0
50
100
150
200
250
300
Epilimnion HypolimnionInitial
DOM p < 0.001
ZP p < 0.001
Depth p = 0.090
DOM*ZP p = 0.187
DOM*Depth p = 0.077
ZP*Depth p = 0.009
DOM*ZP*Depth = 0.65
+ Zoop + Zoop
Phytoplankton Biomass
Treatment
Initi
al
- DO
M
+ D
OM
- D
OM
+ D
OM
- DO
M
+ D
OM
- D
OM
+ D
OM
Bio
ma
ss
(µ
g L
-1)
0
50
100
150
200
250
300
Epilimnion HypolimnionInitial
DOM p < 0.001
ZP p < 0.001
Depth p = 0.090
DOM*ZP p = 0.187
DOM*Depth p = 0.077
ZP*Depth p = 0.009
DOM*ZP*Depth = 0.65
+ Zoop + Zoop
+
-
Total Zooplankton Biomass
Treatment
Initi
al
- DO
M
+ DO
M
- DO
M
+ D
OM
Bio
ma
ss
(µ
g L
-1)
0
200
400
600
800
Epilimnion HypolimnionInitial
DOM p = 0.010 Depth p = 0.003 DOM*Depth = 0.21
Zooplankton:Phytoplankton (H:A) Ratio
Treatment
Initi
al
DO
M -
DO
M +
DO
M -
DO
M +
Zo
op
lan
kto
n B
iom
as
s:P
hyto
pla
nk
ton
Bio
ma
ss
0
5
10
15
20
25
30
Epilimnion HypolimnionInitial
DOM p = 0.002 Depth p =0.216 DOM*Depth = 0.585
No Terrestrial
Resource Subsidy
(-DOM)
With Terrestrial
Resource Subsidy
(+DOM)
(H)
(A)
Initial
(H) (H)
(A)
(H)(H)
(A)
DOM & Transparency: Vertical overlap of Consumers and their Resources
• Do we see variations in DOM and transparency in alpine lakes among years?
• What are the implications of these transparency changes for vertical overlap of consumers and their resources?
Lake Oesa, Canadian Rocky Mountains UV Transparency July 28, 2008-2009
0
2
4
6
8
10
12
14
16
10 100
Dep
th (
m)
380 nm UV (% of subsurface)
2008
2009
0
5
10
15
20
25
30
35
10 100
Dep
th (
m)
380 nm UV (% of subsurface)
2008
2009
0
5
10
15
20
25
30
35
0 10 20 30
Dep
th (
m)
CDOM fluorescence
2008
2009
0
5
10
15
20
25
30
35
0 10 20 30 40 50 60
Dep
th (
m)
Turbidity
2008
2009
0
5
10
15
20
25
30
35
0 200 400
Dep
th (
m)
Chlorophyll Fluorescence
2008
2009
Lake Oesa Hesperodiaptomus July 28
0
5
10
15
20
25
30
35
0.00 1.00 2.00 3.00
Dep
th (
m)
Copepods per Liter
2008
2009
Oesa Zooplankton & Chlorophyll July 28
0
5
10
15
20
25
30
35
0.00 1.00 2.00 3.00
Dep
th (
m)
Copepods per Liter
2008
2009
10% UV380
0
5
10
15
20
25
30
35
0 200 400
Dep
th (
m)
Chlorophyll Fluorescence
2008
2009
Lake Oesa Transparency vs. Precipitation (PRELIMINARY: N= 4 only!!!)
Indirect Effects on Terrestrial DOM?
Low – Medium - High
Terrestrial Vegetation
DOM in water
Indirect Effects of Climate Change: Wildfire
Bark Beetle Damage
Lakes are Good Sentinels & Integrators of Climate Change: Direct & Indirect Effects
Williamson et al. 2009 Limnol. Oceanogr. 54:2273
Specific Conclusions
Higher DOM will stimulate producer biomass more than consumer biomass, reducing consumer regulation of autotrophic production and fate of fixed carbon.
Shorter, interannual climate-induced variations in DOM and other variables can alter transparency and consumer-resource interactions.
Acknowledgements Field and Laboratory Assistance:
– Jeremy Mack, Kevin Rose, E. Overholt, R. Moeller, S. Lee, A. Nurse, N. McCulligh, M. Collado, A. Tucker and M. Cohen
Funding: – USA National Science Foundation, Miami University
Extra Slides Follow
Net Zooplankton Grazing Effect
Treatment
DOM
-
DOM
+
DOM
-
DOM
+
Ne
t G
razin
g E
ffe
ct
(ml
cle
are
d/u
g z
oo
pla
nk
ton
/we
ek
)
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
Epilimnion Hypolimnion
DOM < 0.001 Depth = 0.992 DOM*Depth = 0.839
Changes in DOC (% yr-1) (up to 100% in past 15-20 yr in some areas)
Monteith et al. 2007
Nature 450:537
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