Research

Final Report

Additional
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about the Elwha

PNW Funded Projects
2001
2000
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1995

PNW Project Overview 1998

The Importance of Marine-Derived Nutrients for Ecosystem Health and Productive Fisheries 

Principal Investigator:  
Brian D. Winter, National Park Service, Olympic National Park

Awarded: $12,000

Project Description:

Upon their return from the sea, anadromous salmonids provide marine-derived nutrients to freshwater ecosystems through their excretion, gametes, and carcasses. These nutrients are important to the productivity of the lakes and streams in which they spawn. Since low levels of primary and secondary productivity are typical of many coastal streams in the Pacific Northwest, Larkin and Slaney (1997) concluded that even modest inputs of nutrients and carbon from relatively few anadromous fish may be important in stimulating primary production and maintaining trophic productivity.

The influx of anadromous salmonids was historically important to subsequent Olympic Peninsula salmon runs and their ecosystems. Declines of these runs, for various reasons, have undoubtedly reduced stream productivity and nutrient availability to terrestrial ecosystems. Scientific analysis is proposed to assist in the identification of escapement levels that sustain both productive fisheries and healthy ecosystems. Since removal of Elwha Dam could begin in about three years and three years of baseline data would provide a minimum data set to account for natural variation, sample collection should begin this year. Following dam removal and fish restoration, this baseline data will be compared to data collected from the restored ecosystem to identify the importance of marine-derived nutrients to fish and ecosystem productivity and contrasted with the results from data collected from the Lyre River and Twin Creek.

Project Status:
Final report completed June 2000.

Final document citation:
Winter, B.D., R. Reisenbichler, and E. Schreiner.  June 2000.  The Importance of Marine Derived Nutrients for Ecosystem Health and Productive Fisheries.  Olympic National Park, National Park Service, U.S.Department of the Interior.  32 pages.

Final Report Abstract:
This study was composed of two parts.  The purpose of the first part was to establish baseline values for marine derived nutrients (MDNs; stable isotope ratios for nitrogen and for carbon) for various trophic levels in the Elwha River ecosystem.  This information will allow comparisons with similar measurements following restoration of the ecosystems and native anadromous fish runs after removal of the Elwha and Glines Canyon dams.  Similar relationships were investigated in the Lyre River to provide important scientific comparisons and controls and to broaden the applicability of the results.  The second part evaluated the spatial variability of nitrogen and carbon stable isotope ratio values within and between various coastal Washington river systems.  This work used stonefly larvae to test for (1) year-to-year retention and accumulation of MDNs and (2) differences between mainstem reaches and tributaries.

Fish samples provided the largest contrast in isotope values between areas with and without salmon carcasses in the Elwha and Lyre systems.  In general, rainbow trout below Elwha Dam had greater nitrogen and carbon stable isotope ratio values than fish above the dam or above anadromous fish migration barriers in the Little River and Lillian River.  This relationship was similar for the trout above and below a migration barrier in the Lyre River.  The aquatic invertebrate results were inconsistent, while the results for mosses and leaves were inconclusive.

Researchers found substantial variation in background values for nitrogen stable isotope ratio of stonefly larvae (i.e. in larvae from areas with no salmon).  Such variation has important implications for the design of studies to estimate the importance of MDNs in aquatic and terrestrial ecosystems.  Evidence for modest retention of MDNs was found in the aquatic invertebrate community from one year to the next, and differences between tributaries and mainstem reaches were found that suggested distinct temporal dynamics and ecosystem effects of MDNs between these two habitats.

Both study parts are essentially snapshots in time.  Additional sampling in future years is necessary to determine if the trends uncovered remain over time.  This may be critical if fisheries managers are to use marine-derived nutrient levels in fish to develop ecosystem-based spawning escapement goals.

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