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Disturbance of benthic algae by spawning Pacific salmon in
Thompson Creek, MIJessica Kosiara
School of Biological Sciences
Lake Superior State University
Pacific salmon in the Great Lakes
• Introduced to control alewife
• Have since become a recreational asset
• Little is known of their ecological impact
Pacific salmon life history
• Anadromous and semelparous• Accumulate 95% of
mass in ocean (Groot and Margolis 1991)
• Marine derived nutrients
SalmonNutrients
Water
Algae
Effect On Benthic Community•Studies demonstrate varying responses
•Results of meta-analysis show effects are site dependent (Janketski et al. 2009)
Algae V.S. Algae
Spawner Density
Spawner Species
Substrate Size
The Big Picture
Salmon
Nutrients
Disturbance
Competition
Pollutants
Water Chemistry
Algae
Consumers (inverts, fish)
Objective: to assess overall impact of Pacific salmon in Great Lakes tributaries
Research objective
Salmon
Nutrients
Disturbance
Competition
Pollutants
Water Chemistry
Algae
Consumers (inverts, fish)
To assess impact of salmon on algal biomass through nutrient enrichment and disturbance
Study site
Thompson Creek– Fall run of Chinook and
coho salmon
– Dam which prohibits salmon movement upstream
Experimental design• Each reach has 3 exclosure
plots and 3 open plots
• 4 treatments– Experimental-open
– Experimental-exclosure
– Reference-open
– Reference-exclosure Open Plot
ExclosurePlot
Reference Reach
Experimental Reach
Direction Of Flow
Plot set-up• 1m x 1m plots
• 3 blocks with 4 tiles each per plot
• Set in substrate for algal colonization
Field sampling• Conducted before, during and after 2009
salmon run – 1 tile collected per set (n=3 per plot)
– Measured canopy cover with densiometer
– Debris cleared from exclosures weekly
Lab analysis
• Tiles scrubbed • Analyzed for chl a and
Ash-Free-Dry-Mass (Steinman et al. 2006)
• Invertebrates collected from tiles– Functional feeding
group identified
Data analysis
• 2 way ANCOVA– Main factors• Treatment (Experimental-open, experimental-
exclosure, reference-open, reference-exclosure)
• Time (before, during and after)
– Grazers, and canopy cover analyzed as covariates
Observations• Aggregation of fine sediments on tile in exclosure
plots
• Tiles in open plots covered by large substrate
Conclusion
• Physical abrasion of tiles
• Substrate displacement and aggregation
Salmon
Nutrients
Disturbance
Water Chemistry
Algae
Implications to Stream Food Webs
Algae
Consumers?
•May decrease consumers–Limited spawning habitat + high number of spawners = compounded effects
•May not affect consumers–Alternative food resources available–Localized effects
Great Lake Streams
• Site dependent– Variability in available
spawning grounds
– Salmon runs tend to be smaller
– Small sediments, mostly sand (low algae)
Algae
Consumers?
Acknowledgements
Dr Moerke
Dave Janetski (UND)
LSSU and UND undergrads
Randy Espinoza (MDNRE)
Great Lakes Trust Fund