Lake Superior

Grants No. 0528674 (NSF) and NA06OAR4170017 (NOAA)

Created by: Helen Domske, NY Sea Grant. Information/Photos: Cindy Hagley and Jeff Gunderson, MN Sea Grant.

Lake Superior

NOAA GLERL

7

Ecosystem: Generally Good• Fisheries good to excellent• Lower food web stable• Contaminants generally decreasing or

stable• Forest cover increasing• Important designations

SOLEC 2011

Lake Superior Ecosystem Challenges

Source: MN Sea Grant

Round Goby

Emerald Ash Borer

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0 100 200 300 400 500

Mys

isab

un

dan

ce (N

um

ber

m-2

)

Bottom depth (m)

2006 2005 1971

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500

1000

1500

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3000

3500

0 25 50 75 100 125 150 175 200 225 250 275 300 325

Dip

ore

ia s

pp

. ab

un

dan

ce

(Nu

mb

er m

-2)

Bottom depth (m)

1973 2005 2006

Trends in Key Lower Food Web Prey Species

Diporeia spp.

Mysis diluviana

SOLEC 2011

Lake Superior water is clear!Lake Superior water is clear!

• Secchi Disk– Measures water

transparency– Anything that

interferes with light penetration (Particles, algae, sediment)

Photo: M. Auer, MTU

Water ClarityWater Clarity

16

11

26

3

Lake Superior Water Stays Put

Lake Superior Water Stays Put

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Superior Michigan Huron Erie Ontario

Retention Time for each of the Great Lakes

Ret

entio

n Ti

me

(yea

rs) The average amount of

time a drop of water stays in the lake

Pollution implications for Lake SuperiorPollution implications for Lake Superior• Small drainage basin

– Less pollution coming in• BUT very long retention time

– Pollutants accumulate and remain for a long time

• Domestic Water Use• Navigation• Fish Habitat• Hydropower

Water Use Priorities

A Superior Lake…...

Habitat

Photos: UW Extension Source: SOLEC 2011

Coastal Wetlands and Nearshore Areas

• Critical habitat for fish, aquatic organisms, and wildlife• Very productive compared to all other Lake Superior

habitats

1 FT

6 IN.

Small changes in Water LevelMake a BIG difference in

Coastal Habitats

….even a difference as small as a few inches

Water Temperature, Air Temperature, and Ice Cover

on Lake Superior

Figures from Jay Austin, UMD

Lake Superior Erosion

Lake Superior Mining

Duluth Superior Ore Dock

Source: Minnesota PCA

Habitat DestructionFrom Mining Operations

• Open pit mining -- destroys lakes & wetlands, alters watersheds

• Mining generates waste rock and mine tailings

• Tailings basin infillings could destroy wetlands and wildlife habitat

SOLEC 2011

SHIPPINGLake Superior is connected to the Atlantic Ocean by the St. Lawrence Seaway. The 2,343 mile (3,770 kilometer) trip by boat from Duluth/Superior to the ocean takes about 7 days.

Duluth/Superior is the busiest inland port in the country, with more than 1,000 vessels visiting annually.

Taconite (pelletized iron ore) and coal are the major domestic cargoes. Taconite is shipped to steel mills on the lower Great Lakes. Low-sulfur western coal is shipped to Michigan, where it is burned to generate electricity. MN Sea Grant

The introduction of sea lamprey and rainbow smelt, as well as over-fishing, have depleted the populations of whitefish and lake trout that form the core of the Lake Superior fisheries. The sea lamprey control program implemented by Canada and the United States has been quite effective.Source: University of Guelph

THE FISHERY For all its size, Lake Superior has less capacity to support aquatic life than do the other Great Lakes. Lake Superior is ultra-oligotrophic, which means it has less dissolved nutrients available to support aquatic life. As a result, the Lake Superior fishery produces only about 10% of what Lake Michigan, a comparatively nutrient-rich lake, produces annually.

Lake Superior Fishery Change

• Chemical Pollution• Sedimentation• Commercial Fishing• Recreational Fishing• Habitat Loss• Climate Change

• Exotic Species

State of Lake Sturgeon• Lake sturgeon numbers are increasing

• For the first time in 100 years, spawning naturally in St. Louis River

• Demonstrates progress from 30 years of habitat restoration and stocking efforts

Healthy Lake Trout Populations

0

0.4

0.8

1.2

1.6

2.0

2.4

197019

7319

7619

7919

8219

8519

8819

9119

9419

9720

0020

0320

0620

09

Year

Sis

cow

et/1

000

m n

et n

igh

t Siscowet CPUE

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195119

5519

5919

6319

6719

7119

7519

7919

8319

8719

9119

9519

9920

0320

07

Year

Lak

e Tr

ou

t/ 1

000

ft o

f N

et Lean Lake Trout CPUE

Source: Lake Superior Technical Committee data

Lake trout and siscowet populations in Lake Superior

Lake Superior Herring Fishery

• Lake herring also called tullibeesor ciscoes

• Historically, most abundant native fish

• Harvested across Lake Superior

Lake Herring

Photo: MN Historical Society

• Introduced into a Michigan inland lake in 1912, whose outflow went into Lake Michigan -- 1923

• Found in Lake Superior in the 1930s• Found along North Shore in 1946, after which populations

exploded

Rainbow Smelt Introduction

Smelt Impacts

Contributed to declines in native fish populations such as lake herring and lake whitefish

HerringFisherman

Unlike the invasion of lamprey, smelt at least created a commercial fishery

Pound net in St. Louis River

Pink Salmon• Pink salmon “accidentally released” in Thunder

Bay in 1956• Currently are naturally reproducing in small

numbers

Pink Salmon