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Effects of Marine-Derived Nutrients on Productivity in Sockeye Systems

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Title: Effects of Marine-Derived Nutrients on Productivity in Sockeye Systems


1
Effects of Marine-Derived Nutrients on
Productivity in Sockeye Systems
2
Collaborative Project Funded by Watersheds
Initiative of the Gulf Ecosystem Monitoring (GEM)
Component of EVOS IMS/UAF Bruce Finney Terry
Whitledge Dean Stockwell Melanie
Rohr ADFG/Kodiak Steve Honnold Switgard
Duesterloh Steve Thomsen
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General Rationale for EVOS Initiative
Marine-Derived Nutrients from Salmon may be
Important in Aquatic and Terrestrial Ecosystem
Processes Traced into Freshwater Plankton,
Juvenile Anadromous and Resident Fish Traced
into Riparian Vegetation and Terrestrial
Animals MDN Fluxes are Linked to Ocean
Processes Through Climate, Fishing, Oil Spills
Ecosystem-Based Management Needs Data to
Determine MDN Pathways, Ecosystem Importance and
Monitoring Protocols Basic Research Needed!
5
Study Design Sampling Sockeye (Karluk) and
Control (Spiridon) Lakes 3 Year Study 9
Samplings/year (April - October) 2 Lake and 2
River (mouth) Stations at Each Lake Full Water
Column Sampling (5 m intervals to bottom)
6
Site Characteristics
Karluk Spiridon Elevation
(ft) 368 446 Watershed area (106 m2)
275 54 Lake area (106 m2) 39.4
9.2 Volume (106 m3) 1920 319 Mean
depth (m) 48 35 Residence time (yr)
4.6 8.0 Anadromous YES
NO Stocked Long-term limnological and
salmon data available
7
Study Design Analyses Temperature, DO, pH,
light TP, dissolved P, NO3-, Si Chlorophyll,
POM, phytoplankton, zooplankton, juvenile and
adult salmon Primary Productivity Stable
Isotopes (d15N, d13C) on POM, periphyton,
zooplankton, juvenile and adult
sockeye Exploratory Studies d15N, d13C on
terrestrial plants, bears, birds
8
Unique Study Relatively well-matched pair of
lakes, except for salmon Previous Limnological
and Paleoecological data show strong impact of
MDN in Karluk Lake Detailed spatial and
temporal sampling Measuring primary
productivity Complete/integrated stable
isotope analyses d15N enriched in salmon
carcasses - tracer of MDN
9
Comparison of Limnological Profiles Between Lakes
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Same for Early October
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Summary Part 1 (Limnology) Similar physical
regime Very different ratios of major
nutrients Spiridon P-limited Karluk P, Si and
N limited Consistent with MDN source MDN
high P, zero Si Higher algal standing stock in
Karluk by 4X
17
Comparison of seasonal cycles between lakes and
rivers
18
River spawners
Beach spawners
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Surface
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Summary Part 2 (Temporal perspective) Karluk
Lake higher Chl a and primary productivity by
5X d15N higher in Karluk Lake and river
phytoplankton (POM), zooplankton and juvenile
sockeye relative to Spiridon Lake Differing
seasonality Late summer/early fall peaks in Chl
a, primary productivity, biota d15N and some
nutrients in Karluk Temporal relationships
suggests influence from the early, river spawning
run of sockeye reasonable lag between escapement
at downstream weir, rivers and open lake
stations Transfer into higher trophic levels
indicated Data support hypothesis that MDN is
main control
26
Thanks to EVOS/GEM for funding Phil Mundy The
dedicated field and lab personnel
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Controversy? Two Views Salmon-derived nutrients
are essential to freshwater and terrestrial
ecosystems, and are key to the restoration and
sustainability of salmon Salmon-derived
nutrients are not that important, and the
top-down effects of escapement on lake ecosystems
is substantial
30
Salmon-Derived Nutrients -Productivity Feedback
Freshwater Productivity
Nutrients
Juveniles
Spawner Abundance (escapement)
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