How Will Climate Change Affect Trophic Processes and Productivity in Freshwater-Riparian Ecosystems?...
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Transcript of How Will Climate Change Affect Trophic Processes and Productivity in Freshwater-Riparian Ecosystems?...
How Will Climate Change Affect Trophic Processes and Productivity in
Freshwater-Riparian Ecosystems?
Mark S. Wipfli
USGS Cooperative Fish and Wildlife Research UnitSchool of Fisheries and Ocean Sciences & Dept of Biology and Wildlife
Institute of Arctic BiologyUniversity of Alaska Fairbanks
I. Aquatic Food Webs
II. Climate Change Effects on Food Webs
• Freshwater habitat loss from drying
• Water temperature increases
• Terrestrial vegetation cover changes
• Nutrient loading – from land and sea
Today’s talk
FISH BIRDS
nutrients
algae and aquatic plants
herbivorous invertebrates
carnivorous invertebrates
Aquatic food web (streams, wetlands)
Terrestrial prey ingestion by fishes
Cutthroat trout
May June July Aug Sept Oct0.0
1.0
0.2
0.4
0.6
0.8
Pro
port
ion
of t
erre
stria
l pr
ey in
gest
ed
Juvenile coho salmon
Dolly Varden char
Wipfli 1997
Climate Change Effects
• Freshwater habitat loss from drying
• Water temperature increases
• Terrestrial vegetation cover changes
• Nutrient loading – from land and the sea
Climate Change Effects
• Freshwater habitat loss from drying
Riordan et al. 2006
↑ drying = ↓ aq habitat, ↓ aq production Result:
Climate Change Effects
• Water temperature increases
Shrinking water body size, warmer soil and air temps, and longer growing seasons will all likely lead to higher water temperatures
↑ temps = ↑ aq production (to a point), ∆ community composition
Result:
Climate Change Effects on Vegetation
• Expansion of shrubs (alder, willow, dwarf birch) and spruce along aquatic habitats.
Sturm et al. 2001
Kugururok R
Climate Change Effects
• Terrestrial vegetation cover changes (valley bottom)
USDA Coop Ext
Invertebrates on riparian plants
0
0.5
1
1.5
2
2.5
3
Alder
Spruce
Hemlo
ck
Salm
onberry
Stink
curra
nt
Blueb
erryIn
ve
rte
bra
te m
as
s (
mg
) /
lea
f m
as
s (
g)
Allen et al. 2003
Coniferous
Deciduous
Result:
↑ rip veg = ∆ food supply ↑ litter ↑ invert production (?) ∆ invert community comp
Tape et al. 2006
1949
2000
Kugururok River
Climate Change Effects
• Terrestrial vegetation cover changes (headwaters)
Active stream channels and gravel bars in 1949 are now colonized by shrubs – alder, willow, dwarf birch.
Spruce riparian
Inve
rteb
rate
bio
mas
s ex
port
ed(m
g dr
y m
ass·
m-3 w
ater
)
0
2
4
6
Conifer Alder
p < 0.05
Piccolo and Wipfli 2002
Aq. invertebrate drift density
Maybeso Drainage
Alder riparian
Result:
↑ deciduous veg = ↑ food for aq consumers
Sturm et al. 2005
Climate Change Effects
• Nutrient loading – from land
Result (?):
↑ nutrients (N + P) = ↑ aq production ∆ invert composition
Hobbie et al. 1999Benstead et al. 2005
Stream nutrient addition studies led to higher aq production in Kuparuk studies.
Bilby et al. 1996, 1998Heintz 2004Wipfli et al. 1998, 2003, 2004
Anadromous fish runs enrich streams with nutrients
• Shown to increase aquatic productivity in Alaska & the PNW
↑ nutrients (N + P) = ↑ aq production (all trophic levels) ↑ fish growth rates, production, lipid levels
Climate Change Effects
• Warming ocean currents
Salmon distributions shift northward (Welch et al. 1998)
Climate Change Effects
• Nutrient loading – from the sea
Result (?):
↑ nutrients (N + P) = ↑ aq production ∆ invert community composition
Summary – hypothesized climate change effects
• Increased temperatures = ↑ invertebrate production ∆ invertebrate community composition ∆ seasonal occurrence
• Terrestrial veg expansion = ↑ invertebrate abundance ∆ invertebrate community composition ∆ seasonal occurrence
• Nutrient loading = ↑ invertebrate production ∆ invertebrate community composition
∆ seasonal occurrence
Summary – hypothesized climate change effects
• Increased temperatures = ↑ invertebrate production ∆ invertebrate community composition ∆ seasonal occurrence
• Terrestrial veg expansion = ↑ invertebrate abundance ∆ invertebrate community composition ∆ seasonal occurrence
• Nutrient loading = ↑ invertebrate production ∆ invertebrate community composition
∆ seasonal occurrence
Summary – hypothesized climate change effects
• Increased temperatures = ↑ invertebrate production ∆ invertebrate community composition ∆ seasonal occurrence
• Terrestrial veg expansion = ↑ invertebrate abundance ∆ invertebrate community composition ∆ seasonal occurrence
• Nutrient loading = ↑ invertebrate production ∆ invertebrate community composition
∆ seasonal occurrence
Summary – hypothesized climate change effects
Physical processes dictate biological outcomes in riverine systems
Erosion & sediment deposition
Riparian plant community development
Leaf litterinputs
Terrestrial invertebrateinputs
Terrestrial ecosystem
Freshwater ecosystem
Elevated basal food resources for fish & other consumers