Research
PNW
Funded Projects
2001
2000
1999
1998
1997
1996
1995
PNW Project Overview 2000
Effects of Marine Derived Nutrients on Aquatic Macroinvertebrate Production in Salmon Spawning Streams
Principal
Investigators:
Dr.
Robert
Gara,
University of Washington, College of Forest Resource
Jon
Honea,
University of Washington, College of Forest Resources, PhD Candidate
Awarded: $44,850
Project
Description:
The
decline of Pacific Northwest anadromous salmonids has resulted in the
listing of some stocks as threatened or endangered under the Endangered
Species Act.
The socio-economic stability of the affected regions depends on the
ability of land managers and regulators to successfully direct land use
practices in a manner consistent with the survival and recovery needs of
the listed salmonids.
This is only possible with a specific understanding of the species
and its ecology.
A fundamental component of a species’ ecology is its trophic
linkages with other organisms.
A primary trophic interaction of anadromous salmonids appears to
involve the release of marine-derived nutrients (MDN) from spawning adults
and later from their spawned-out carcasses.
Other research has found that many types of organisms inhabiting or
visiting streams and riparian areas utilize MDN.
This MDN fertilization, repeated with each spawning, benefits
juvenile salmonids that may remain in streams for up to three years after
hatching, depending on species.
Aquatic life stages of macroinvertebrates probably play an
important role in the transfer of MDN from adult to juvenile salmonids.
To discover how macroinvertebrates facilitate the transfer of MDN
from adult to juvenile salmonids, this project will quantify the pathways
of MDN to macroinvertebrates by monitoring the response of aquatic
macroinvertebrate production to salmon carcass decomposition.
These production estimates will provide a measure of the total
energy available to higher consumers, including juvenile salmon.
In addition, the project will evaluate the relative importance of
the different pathways of MDN to aquatic macroinvertebrates by monitoring
changes in production in each of the major trophic categories of aquatic
macroinvertebrates.
Finally, the project will determine if juvenile salmon benefit from
MDN at the study sites, as has been shown elsewhere.
By characterizing the transfer of MDN via these trophic linkages,
this research will not only describe the capacity of aquatic
macroinvertebrates to serve as a link between adult and juvenile salmon,
it will also identify parameters – such as taxa presence/absence,
density, community composition, etc. – that can be monitored to evaluate
the effectiveness of conservation and restoration practices.
Project Status:
Project
Progress:
In
October 1999, researchers began intensively sampling upstream and
downstream of a natural anadromous fish barrier on Kennedy Creek in the
southeast region of the Olympic Peninsula and continued sampling
throughout the year 2000.
Over 200 benthic macroinvertebrate samples have been collected.
The size-frequency method will be used to estimate annual
macroinvertebrate production.
Preliminary analyses of samples show a substantial reduction in
macroinvertebrate numbers, biomass, and diversity in the spawning reach
due to redd formation followed by rapid recovery after the adult spawners
die and decompose, releasing MDN into the stream food web.
Stable isotope analysis of the relative concentrations of 12C
to 13C and 14N to 15N in salmon and
insect tissue will determine whether increases in insect production can be
attributed to MDN from adult salmon and whether insect production is
supporting the production of juvenile salmon.
Preliminary analyses of samples show a substantial fraction of
marine-derived carbon in insects in the spawning reach.