Todd D. CrailPhilip M. Mathias, Johan F. Gottgens, Jon M. Bossenbroek

The University of Toledo

Wind-derived seiches as a means for detecting and monitoring the unionid community in the

western basin of Lake Erie

My Questions

• Increasing number of refuges…

• Are unionids found anywhere else, such as the in-shore marshes and near-shore open lake habitats?

• Can I sample them? And how?

• Richness? Recruitment?

• Historic sequence in shell material?

Sampling Sites

Luna Pier

Bayshore

Maumee Bay SP

Turtle Creek

Ottawa NWR

Toussaint Creek

East Harbor

Winous Point

Lake Erie

N• Eight sites

“qualitatively” sampled 2003-2008

• Sites open to lake, with dreissenids present

• Most sites also had diked marshes

• Recovered live individuals of at least two species at all sites

Sampling Sites – “Marshes”

• First sites sampled were drowned river mouths and hemi-marsh

• Methods were tactile and a modified basket rake

• Timed searches, measured shell length, and classified as live, fresh dead, weathered and sub-fossil

• Mobility increased greatly using snow shoes

Sampling Sites – “Marshes”

• Diked marshes had four species live – Pyganodon grandis – Giant Floater– Toxolasma parvus - Liliput – Uniomerus tetralasumus – Pondhorn– Utterbackia imbecillis – Pond Papershell

• Open sites had up to seven species live

– Leptodea fragilis - Fragile Papershell – Lasmigona complanata - White Heelsplitter – Potamilus alatus - Pink Heelsplitter – Giant Floater– Quadrula quadrula - Mapleleaf

• Refer to Bowers & de Szalay 2004, American Midland Naturalist

• Noticed the profound effect of seiches & how it simplified sampling

http://en.wikipedia.org/wiki/Seiche

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Example Seiche (2003)

Example Seiche – Bayshore Road (2006)

One meter seiche during low water

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One meter seiche during low water

Example Seiche – Bayshore Road (2006)

Bayshore - 2006• Four species recovered live

– Amblema plicata – Threeridge– Fragile Papershell– Giant Floater– Pink Heelsplitter

• In a 20 minute timed search, we found, measured, recorded and replaced 34 individuals (3 species)

– Roughly 35 seconds per individual

• In an additional 25 minute search, we found 5 live threeridge

• Found 6 species fresh dead to lightly weathered

• Found 3 species sub-fossil

• The farther the seiche went out, the greater the abundance of live mussels

Bayshore - 2006• Fragile Papershell

– 28 individuals– Length was 29 – 114 mm– Mean Length was 74 mm

• Threeridge – 5 individuals– Length was 59 – 80 mm– Mean Length was 71 mm

Bayshore - 2006

• Rate of dreissenid infection was < 10 dreissenids on any individual except (1) 109 mm fragile papershell (19)

Partitioning of Habitat?

RED – Fragile Papershell BLUE – Threeridge Green – Giant Floater

Time Series

20062000199519901985198019751955 19651960 1970

Sub-Fossil Weathered Fresh Dead

More accurately account for time since death, since we can age live dreissenids inside the shell?

Time Series

20062000199519901985198019751955 19651960 1970

Sub-Fossil Weathered Fresh Dead

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Weathering is a spectrum depending on the system and species

Time Series

20062000199519901985198019751955 19651960 1970

Sub-Fossil Weathered Fresh Dead

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Fossilization is a spectrum process as well but…

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Time Series

20062000199519901985198019751955 19651960 1970

Sub-Fossil Weathered Fresh Dead

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Fossilization is a spectrum process as well but…Why aren’t sub-fossil species found in the current assemblage?

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Time Series

20062000199519901985198019751955 19651960 1970

Sub-Fossil Weathered Fresh Dead

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Fossilization is a spectrum process as well but…Why aren’t sub-fossil species found in the current assemblage?Why aren’t weathered, fresh dead & live species found in the

sub-fossil assemblage?

?

Winous Point Marsh Conservancy - 2006

• 6 species live (white heelsplitter, fragile papershell, pink heelsplitter, giant floater, lilliput, pond papershell)

• 4 species fresh dead (threeridge, Obliquaria reflexa - threehorn wartyback, mapleleaf, pimpleback)

Bayshore & Maumee Bay SP - 2008

• ~0.5 meter seiche event

• At Bayshore Road– 32 individuals / 3 species – 28 were fragile papershell

• mean length of 55 mm • mean length of 74 mm in 2006

• At Maumee Bay SP– 22 individuals / 2 species– 17 were fragile papershell

• range 16 – 112 mm• mean length was 38 mm• mode was 29 mm

– Continuous distribution – 6 weathered species

More Partitioning of Habitat?

RED – Fragile Papershell BLUE – Threeridge Green – Giant Floater

More Partitioning of Habitat?

RED – Fragile Papershell BLUE – Threeridge Green – Giant Floater

Is this evidence of ontogenic shifts? Or is it just a population sink?

YELLOW – Papershell, Floater and Pink Heelsplitter Juveniles!

Bayshore - 2008

• (4) 100 meter transects with a modified BR-12 basket rake– www.shellfishing.com

• No live species

• Is the Missouri Trawl the answer?

Substrates

Higher Quality Substrate?

Potamogeton crispus, Lyngbia sp. and Dreissenia building substrate deepenough for Unionids to burrow

Higher Quality Substrate?

140 mm white heelsplitter in Dreissenid fortified fine silt(other Unionid species present as well)

Ponar Sampling at Bayshore 2010

Our Ponar Rig

Ponar Sampling at Bayshore 2010

Sediment Dry Mass from Bayshore Outlet to Maumee Bay State Park

R2 = 0.43

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Ponar Sampling at Bayshore 2010

Sediment Dry Mass from Bayshore Outlet to Maumee Bay State Park

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Ponar Sampling at Bayshore 2010

Sediment Dry Mass from Bayshore Outlet to Maumee Bay State Park

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Ponar Sampling at Bayshore 2010

Sediment Dry Mass from Bayshore Outlet to Maumee Bay State Park

R2 = 0.43

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Ponar Sampling at Bayshore 2010

Sediment Dry Mass from Bayshore Outlet to Maumee Bay State Park

R2 = 0.43

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Ponar Sampling at Bayshore 2010

Ponar Sampling at Bayshore 2010

Site 2

Ponar Sampling at Bayshore 2010

Site 11

Ponar Sampling at Bayshore 2010

Site 18

Lake-Influenced Maumee River 2010

• Live fragile papershell, deertoe, threehorn wartyback, threeridge, mapleleaf, pimpleback, pink heelsplitter, white heelsplitter, giant floater, liliput, wabash pigtoe, fat mucket

Lake-Influenced Maumee River 2010

• Live fragile papershell, deertoe, threehorn wartyback, threeridge, mapleleaf, pimpleback, pink heelsplitter, white heelsplitter, giant floater, liliput, wabash pigtoe, fat mucket

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Port Clinton 2010

• Fresh Dead shell from fragile papershell, giant floater, threeridge, white heelsplitter, pink heelsplitter, threehorn wartyback, deertoe and pond mussel on a public beach.

Port Clinton 2010

• I hypothesize the success of the community has to do with sediment conveyance

• This resolves fouling, food, and stability

My Questions with Answers

• Unionids are found elsewhere, such as the in-shore marshes and near-shore open lake habitats.

• I can sample them… with luck or hard work

• There’s richness. There’s recruitment.

• There’s an historic sequence in shell material, but it’s different at two times.

More Questions Than Answers

• What is the mechanism?

• Veliger density dependent? Reduction of dreissenid health? Dreissenid predator density? Dreissenid air exposure? Or is it about substrate?

• Or all of the above? Are there factors not considered?

• Where else are they? And how can we find them?

Acknowledgements

• Fellowship with the National Science Foundation GK-12 Program DGE-0742395

• Funding from the Winous Point Marsh Conservancy

• Lake Erie Center & Department of Environmental Sciences

• Field help from Maria Tumeo

• Thoughtful comments from Tom Bridgeman