Thermal heterogeneity in streams: animals
exploit it, models ignore it
Inletkeeper.org
Jonathan B. Armstrong
School of Aquatic and Fishery Sciences, Univ. of Washington
Co-authors: D.E. Schindler, P.J. Lisi
The Wood River watershed: area similar to a GCM grid cell
Armstrong et al. 2010 Ecology
Lisi et al. in review Geomorphology
>10 ̊ C range in
temperature among
tributary streams
stream temperature oC
18
Summer stream temperatures
16
14
12
10
8
6
4
2
04 Jul
18 Jul
01 Aug
15 Aug
29 Aug
Armstrong et al. 2010 Ecology
Lisi et al. in review Geomorphology
How does thermal heterogeneity
affect food webs and consumer
energy budgets
Frequency
Many consumers can acquire the majority of their
It’s important
to eatsurplus
all you exploiting
can, whensalmon
you can.
annual energy
Jul-28
Foraging opportunity
Aug-27
Armstrong & Schindler 2011 Nature
The red wave
Salmon populations spawns for only
2-6 weeks
Resource pulse delivered to a highly
Heterogeneous landscape
How does thermal heterogeneity mediate the ability of
consumers to capitalize on this resource pulse?
1. Physiological effects on stream-dwelling fish
2. Secondary effects on wide-ranging freshwater and
terrestrial consumers
I. Thermal constraints on the potential for juvenile
coho salmon to exploit sockeye salmon eggs
Experimental and observed results: fish <70 mm can’t swallow salmon eggs
Armstrong et al. 2010 Ecology
70 mm
Coho
Length
30 mm
September
May
Time
Juvenile coho salmon grow faster in warmer streams
70 mm
Length
30 mm
September
May
Time
Juvenile coho salmon emerge earlier in warmer streams
70 mm
Length
30 mm
September
May
Time
Bioenergetics simulation
0.9
Feeding
P15Level
80
0.8
70
0.7
50
60
0.6
40
6
8
10
T15 ̊ C
Temperature
12
July-15
August-15
Date
b)
15
15
10
10
Mean daily water tem
Size distributions of coho salmon at
the onset of sockeye salmon spawning
June-15
100
5
5
0
a) Bear
30
40
50
60
70
80
90
100
110
120
130
140
Yako (Y)
Bear
Bear (B)
Yako
S. Salm Whitefish.
Silver Salmon (S) Whitefish (W)
Stream
0
40
b) Yako
30
40
50
60
70
80
90
100
110
120
130
B
140
Y
WF
0
15
c) Silver Salmon
30
40
50
60
70
80
90
100
110
120
130
140
15 30
SS
0
d) Whitefish
30
40
50
60
70
80
90
Fork Length (mm)
100
110
120
130
140
10 km
15
10
5
Bear and Yako Ck. (cold)
0
Modal mass (g)
Whitefish Ck. (warm)
Jun-1
Jul-1
Aug-1
Sep-1
Oct-1
Date
Broader conclusion:
(1) Ecological mechanisms can magnify the effects of temperature
compared to predictions from physiological models
(2) Responses to warming may be highly variable even within a
single watershed
II. Age-1+ coho salmon actively
exploit thermal heterogeneity within
streams
Armstrong et al. in review Ecology
Temperature determines the digestive capacity of coho salmon
0.16
Mass spec. stomach contents
0.14
0.12
0.1
w arm 10C
0.08
cold
post-feeding
0.06
0.04
0.02
0
-10
6C
0
10
20
30
40
50
Tim e after feeding (h)
60
70
80
10C
6.5C
3C
Spatial variation in water temperature exists within streams as well
Thermal heterogeneity in Bear Ck.
15
14
13
11
10
9
8
7
6
5
0
500
1000
1500
Distance upstream (m)
2000
Temperature
12
Spatial mismatch between foraging and food-processing
15
600
14
13
500
400
11
10
300
9
8
200
7
100
6
5
0
0
500
1000
1500
Distance upstream (m)
2000
Temperature
Sockeye per 200m
12
Deploy PIT tag
Antenna Arrays
Nick Hall
1. 0-930m: cold w/ sockeye
3. 1360m and up: warm w/o sockeye
2. 930-1360m: cold w/o sockeye
Feeding forays into the cold downstream region
Age-1 coho salmon-- 24-July: 85 mm 7.1 g
21-Aug: 108 mm 17.6 g
20
2009
High flows homogenize temperatures
in the main channel
10
5
Temperature C
15
upstream
downstream
July-1
2009: especially wet summer
August-1
Date
September-1
10
Main-channel
thermal heterogeneity: gone in wet years
8
location
Wet Years
location
Big Pool
6
10
Temperaturemean.temp
Mean
mean.temp
Temperature
Mean
mean.temp
mean.temp
8
4
8
2
6
0
4
Big Pool
6
10
lower
lower
Upper
middle
middle
4
8
P12
P12
location
location
BigPool
Pool
Big
2
6
Lower
lower
lower
middle
0
4
middle
2007
2007
2008
2008
2009
2009
year
Year
2010
2010
2011
2011
year
Year
2
2
0
0
2007
2008
2009
year
2010
2011
P12
P12
• Flooded off-channel habitat provides hot spots
during wet summers
• Coho movements track shifting mosaic of water
temperature
Key Points
• Fish do not experience the average
temperature of their environment– they
actively exploit thermal heterogeneity
• Habitat patches that are unimportant
under certain climate conditions may be
critical during alternative conditions.
III. Thermal heterogeneity, salmon
phenology, and the foraging opportunity of
wide-ranging consumers
Spawning day of year
Average Stream Temperature oC
Lisi et al. in review Geomorphology
Schindler et al. 2010 Nature
7.8 – 8.7
Hidden Creek
I
8.8 – 13.2
13.3 – 14.8
14.9 – 17.3
II
Lynx Creek
IV
III
I
Each stream ~ 4 km long
Ruff et al. 2011 Ecology
Spatial and temporal variation in egg consumption by
rainbow trout
Sockeye salmon spawn
timing
Egg consumption by
rainbow trout
Rainbow trout surf the “red wave”
ANCOVA (F3,143 = 10.29, P < 0.0001)
Wide-ranging
consumers at the
watershed scale
Schindler et al. in prep
Cumulative Activity at spawning sites
Salmon complete spawning
and die
Few carcasses remaining
Bear Activity
Salmon start spawning
Cumulative Activity at spawning sites
Bear Activity
Cumulative Activity at spawning sites
Gull Activity
Bear Activity
Phenological diversity matters to consumers
Fryxell et al. 2005
Schindler et al. 2010
Sawyer and Kauffman
2011
Searle et al. 2010
Wijk et al. 2012
Ruff et al. 2011
These landscapes will be different in a warmer future…
 Can we really predict biological responses?
 Do we really need to know before we can act?
Gilman et al. TREE (2010)
Alternative perspective
• What we’ve learned in AK: Complexity impedes
scientific prediction, but it promotes ecological
stability and resilience
• Maintain options for animals: keep disturbance
regimes intact, protect habitat heterogeneity and
population diversity—these are tangible ways to
deal with the uncertainties of climate change
Acknowledgements
•
•
•
•
Thanks for the invitation to share work
Co-authors: Daniel Schindler, Peter Lisi
Funding: SAFS, NSF, Moore Foundation
More information at research website:
jbarmstrong.wordpress.com
Climate effects are filtered by habitat
heterogeneity and animal behavior
Pulsed salmon subsidies