How Will Climate Change Affect Trophic Processes and Productivity in Freshwater-Riparian Ecosystems?

1. How Will Climate Change Affect Trophic Processes and Productivity in Freshwater-Riparian Ecosystems? Mark S. Wipfli USGS Cooperative Fish and Wildlife Research Unit School of Fisheries and Ocean Sciences & Dept of Biology and Wildlife Institute of Arctic Biology University of Alaska Fairbanks

2. Today’s talk 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

3. Aquatic food web (streams, wetlands) BIRDS FISH carnivorous invertebrates herbivorous invertebrates algae and aquatic plants nutrients

4. Aquatic food web & riparian linkages Baxter et al. 2005

5. 1.0 0.8 0.6 0.4 0.2 0.0 Aug Sept Oct June July May Terrestrial prey ingestion by fishes Juvenile coho salmon Cutthroat trout Proportion of terrestrial prey ingested Dolly Varden char Wipfli 1997

6. Climate Change Effects • Freshwater habitat loss from drying • Water temperature increases •Terrestrial vegetation cover changes • Nutrient loading – from land and the sea

7. Climate Change Effects • Freshwater habitat loss from drying Riordan et al. 2006 Result: ↑ drying =↓ aq habitat, ↓ aq production

8. 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 Result: ↑ temps =↑aq production (to a point), ∆ community composition

9. Climate Change Effects • Terrestrial vegetation cover changes (valley bottom) Climate Change Effects on Vegetation Kugururok R Sturm et al. 2001 • Expansion of shrubs (alder, willow, dwarf birch) and spruce along aquatic habitats.

10. Result: ↑ rip veg =∆ food supply ↑litter ↑invert production (?) ∆invert community comp USDA Coop Ext Invertebrates on riparian plants 3 2.5 Deciduous 2 1.5 Invertebrate mass (mg) / leaf mass (g) 1 Coniferous 0.5 0 Alder Spruce Hemlock Blueberry Salmonberry Stink currant Allen et al. 2003

11. 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. Kugururok River 1949 2000 Tape et al. 2006

12. Spruce riparian 6 p < 0.05 4 Invertebrate biomass exported (mg dry mass·m-3 water) 2 0 Alder Conifer Alder riparian Aq. invertebrate drift density Maybeso Drainage Result: ↑ deciduous veg = ↑ food for aq consumers Piccolo and Wipfli 2002

13. Climate Change Effects • Nutrient loading – from land Stream nutrient addition studies led to higher aq production in Kuparuk studies. Hobbie et al. 1999 Benstead et al. 2005 Result (?): ↑ nutrients (N + P) = ↑ aq production ∆invert composition Sturm et al. 2005

14. 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 Bilby et al. 1996, 1998 Heintz 2004 Wipfli et al. 1998, 2003, 2004

15. Climate Change Effects • Warming ocean currents Salmon distributions shift northward (Welch et al. 1998)

16. Climate Change Effects • Nutrient loading – from the sea Result (?): ↑ nutrients (N + P) = ↑ aq production ∆invert community composition

17. 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

18. 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

19. 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

20. Summary – hypothesized climate change effects Physical processes dictate biological outcomes in riverine systems Leaf litter inputs Terrestrial invertebrate inputs Elevated basal food resources for fish & other consumers Riparian plant community development Erosion & sediment deposition Terrestrial ecosystem Freshwater ecosystem

21. Questions?!?