Disturbance of benthic algae by spawning Pacific salmon in

Thompson Creek, MIJessica Kosiara

School of Biological Sciences

Lake Superior State University

Exotic species in Great Lakes

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

Bioturbation• Construction of redds displace sediments

and biota

SalmonDisturbance

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

Native Range vs. Great Lakes

Alaska/Pacific NW Great Lakes

•Few studies conducted in Great Lakes

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

Expected ResultsOpen Plot

ExclosurePlot

Nutrient Enrichment

Disturbance

Chlorophyll a

AFDM

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?

Management• Future introductions of Pacific salmon

• Dam removal in salmon streams

Acknowledgements

Dr Moerke

Dave Janetski (UND)

LSSU and UND undergrads

Randy Espinoza (MDNRE)

Great Lakes Trust Fund

Questions?