GREAT LAKES COASTAL WETLANDS: WHAT IS A REFUGE FOR UNIONIDS?

THE EFFECTS OF WATER LEVEL FLUCTUATIONS

Jessica ShermanCentral Michigan University

Introduction

Jessica ShermanB.S. in Biology and Pre-Veterinary

Medicine from the University of FindlayCurrently at CMU for M.S. in

Conservation Biology○ Advisor: Don Uzarski○ Committee: Dave Zanatta, Daelyn

Woolnough, and Brent Murry

Objectives

Locate refuge populations of unionids in Great Lakes coastal wetlands

Measure chemical and physical parameters

Determine if any support unionids or inhibit dreissenid colonization

Methods

Project began in early JuneInitial set up phaseSites revisited at six and 12 weeks

Inner and outer wetland surveyedEmergent stem densities

Grand Traverse Bay

Study Sites

Beaver Island

Garden Island

The Les Cheneaux Islands

Saginaw Bay

Lake St. Clair Delta

North Maumee Bay

Methods

Water Quality MeasurementsMultiparameter Water Quality SondeWater gauges

Water Quality MeasurementsMultiparameter Water Quality SondeWater gauges

Methods

Methods

Dreissenid Colonization Unglazed clay tiles

○ 16x16 cm

Unionid SurveysInitial 1 p-h visual search for live

mussels○ Staked location○ Snorkeled searches

Methods

Unionid SurveysInitial 1 p-h visual search for live

mussels○ Staked location○ Snorkeled searches○ Except…

North Maumee Bay

Methods

Unionid SurveysClam rake surveys

○ Haphazard starting location

Methods

Results

Live Unionids foundLes Cheneaux Islands

○ 1 species ○ 100% fouled

Lake St. Clair Delta○ 10 species ○ 85% fouled

North Maumee Bay○ 2 species ○ 50% fouled

North Maumee Bay

Lake St. Clair DeltaThe Les Cheneaux Islands

= Unionids present

= Unionids absent

Results

Dreissena colonization on tiles only at Saginaw Bay and North Maumee BayHighest 20,741 and 31,007 per m2 ,

respectivelyPresent in open water of all sites studied

Saginaw Bay historically contained 13 unionid species

Ricciardi et al. 1995, Goodrich and Vander Schalie 1932

Saginaw Bay

5,087 per m2

46 per m2

20,741 per m2

* Highest Recorded Dreissenid Colonization Outer wetland higher than inner

North Maumee Bay

0 per m2

821 per m2

31,007 per m2

Results

= No colonization = Colonization

ResultsPhysicochemical Parameters by Region

PC 1

-6 -4 -2 0 2 4 6 8

PC

2

-6

-4

-2

0

2

4

Temperature

Conductivity

Oxygen

Turbidity

TDS

pH

Alkalinity

Water Depth

Substrate Depth

NH3

SRP

NO4

Saginaw BayLes Cheneaux IslandsBeaver IslandLake St. Clair DeltaNorth Maumee BayGarden IslandGrand Traverse Bay

ConductivityAlkalinityTDS

pH

pHTemperatureTurbidity

Water Depth

28%

18.5

%

Results

ResultsLow Water Level Measurements by Region

PC 1

-6 -4 -2 0 2 4 6 8

PC

2

-6

-4

-2

0

2

4Saginaw BayLes Cheneaux IslandsBeaver IslandLake St. Clair DeltaNorth Maumee BayGarden IslandGrand Traverse Bay

0-0.08 m

0.09-0.2 m

> 0.2 m

Low Water Measurements

28%

18.5

%

ResultsWater Level Fluctuations by Region

PC 1

-6 -4 -2 0 2 4 6

PC

2

-6

-4

-2

0

2

4Saginaw BayLes Cheneaux IslandsBeaver IslandLake St. Clair DeltaNorth Maumee BayGarden IslandGrand Traverse Bay

Water Level Fluctuations

0- 0.25 m

0.25- 0.5 m

0.5- 0.75 m

0.75-1.0 m

> 1.0 m

28%

18.5

%

Conclusions

Physicochemical variables in Saginaw Bay & North Maumee Bay appear to support Dreissena colonization

Low productivity could inhibit Dreissena colonization

No correlations between unionid populations and physicochemical factors

Thank you!