Effect of Salmon Derived Nutrients

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Effect of Salmon Derived Nutrients

• Jessie Wu
• BIOL402

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Overview

• Salmon life cycle
• Salmon derived nutrients
• Riparian ecosystem
• Two research papers
• Overall findings
• Future direction

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Salmon Life Cycle
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Salmon Derived Nutrients

• MDN (marine derived nutrients)
• - N15
• Salmon carcass
• Terrestrial system
• - Riparian forests
• Aquatic system
• - Streams and lakes

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Riparian Ecosystem(Gregory et al., 1991)

• Riparian zone interface between terrestrial and
  aquatic ecosystem

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Riparian Ecosystem(Gregory et al., 1991)

• 3 components
• Physical processes biological processes
• - inputs
• - sediments
• - regulator

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Research 1 Effects of salmon-derived nitrogen on
riparian forest growth and implications for
stream productivity (Helfield and Naiman, 2001)

• Objective
• - Examine effects of salmon-borne nutrients on
  the riparian forests of two Alaskan watersheds
• 1. To determine extent to which riparian plants
  acquire MDN from salmon carcasses
• 2. To assess effects of MDN on the basal area
  growth of riparian trees

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Research 1 Study area

• 2 watersheds in Chichagof Island in southeast
  Alaska, USA
• - Kadashan River (30k to 125k)
• - Indian River (200 to 45k)

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Research 1 Method

• August 1998 and 1999
• Reference site and spawning site within each
  river
• 4 transect
• canopy cover, stem density, basal area and
  overstory species composition measured using
  point-centered quarter method
• Foliage and increment core samples (measuring 15N
  isotope)

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Research 1 Result 1
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Research 1 Result 2Mean foliar 15N in Sitka
spruce annual basal growth
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Research 1 Result 3Annual Sitka spruce basal
area growth
Highest basal area growth but no trend
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Research 2 Impact of climatic change and fishing
on Pacific salmon abundance over the past 300
years (Finney and Gregory-Eaves, 2000)

• Objective
• - Use lake sediment records of 15N and
  biological indicators to reconstruct sockeye
  salmon abundance in the Bristol Bay and Kodiak
  Island regions of Alaska over the 300 years
• (Historical records are short, complicated by
  commercial harvesting and habitat alteration)

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Research 2 Study Area

• 7 Alaskan Lakes
• - Frazer and Tazimina are
• control lakes

Tazimina
Karluk
Becharof
Red
Ugashik
Frazer
Akalura
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Research 2 Result 1 Influence of SDN loading,
as represented by escapement/lake area ratio

• Escapement
• The density of adult sockeye
• Returning to the lake
• Ecosystem to spawn

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Research 2 Result 2Historical and
paleolimnological evidence of sockey salmon
variation in Karluk Lake over past 300 yrs

• Prolonged
• Collapse in
• 20th century
• may be due to
• reduction of
• SDN as result
• of overharvest

eutrophic
meso-eutrophic
1985
1939
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Research 2 Result 3Comparison of 15N isotope
profiles from sockeye and control lakess

• SST sea surface temperature
• Early 1800s (decline 15N temp)
• 1850 (decline temp increased
• 15N)
• Last 2 decades (decline)
• Recent increase in Frazer
• (bypass)

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Overall Findings

• Important implication for fisheries management,
  endangered species and ecological restoration
• Large-scale factor (ex. climate)
• Complex interaction
• Variability in SDN impact
• Human impact

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Future Directions

• Interactions VS single dimension approach
• Considered both climatic change and altered
  nutrient cycles
• Recent study
• - keystone species (Helfield Naiman 2006)