Fish Out of Water: The Importance of Salmon and Bears for Productivity of Riparian EcosystemsEPA Grant Number: FP916315
Title: Fish Out of Water: The Importance of Salmon and Bears for Productivity of Riparian Ecosystems
Investigators: Holtgrieve, Gordon W.
Institution: University of Washington
EPA Project Officer: Lee, Sonja
Project Period: January 1, 2004 through December 31, 2006
Project Amount: $109,871
RFA: STAR Graduate Fellowships (2004) RFA Text | Recipients Lists
Research Category: Fellowship - Terrestrial Ecology and Ecosystems , Academic Fellowships , Ecological Indicators/Assessment/Restoration
The objective of this research is to examine linkages between terrestrial and freshwater ecosystems, focusing on the role of highly mobile organisms as vectors of nutrients. Pacific salmon (Oncorhynchus spp.) are extremely rich in nitrogen and phosphorous, and because salmon accumulate most of their biomass while at sea, the return of salmon to freshwater streams represents a large and important flux of resources that, if eliminated, may have broad implications for the healthy functioning of coastal ecosystems. I intend to characterize and quantify links between Pacific salmon, brown bears (Ursus arctos ), and riparian ecosystem functioning in terms of nutrient cycling and primary productivity.
I will address these questions through manipulative experiments in which bears are excluded from areas with historically high feeding activity along a series of streams with varying salmon density. The work will be conducted in the Bristol Bay region of southwest Alaska at the University of Washington's Alaska Salmon Program field stations. To measure the effect of marine-derived nutrients on nutrient availability to plants, year-round changes in biologically important nutrient dynamics will be measured on a monthly basis over the Alaska growing season (May – September) and once over the winter period (October – April). The measurements include ammonium, nitrate, and phosphate pools, rates of net nitrogen mineralization and nitrification, which are strong indicators of nitrogen availability, and emissions of biogenic trace gases (nitrous oxide, carbon dioxide, and methane) from soils as indicators of microbial activity. Salmon spawning in streams typically occurs from mid-July through September, thus it will be possible to quantify changes in nutrient pools through time and correlate them with the arrival of salmon and the presence of bears. Aboveground net primary productivity among treatments will be assessed on a monthly basis during the summer through either biomass harvests of 0.25-m2 sub-plots (grasses) or fine-scale growth increments (trees) within the study plots. Physical characteristics of the ecosystem including soil bulk density and stand density of trees and shrubs also will be measured.
I anticipate that the reductions in marine-derived nutrients through the exclusion of bears will significantly change nutrient cycling rates and reduce riparian ecosystem productivity. By illuminating the mechanisms through which salmon-derived nutrients sustain coastal ecosystems and the role of bears in delivering those nutrients, I will help to provide a framework for watershed-level restoration focused on preserving ecological roles of species within the ecosystem.