GLIN==> U-Mich. news release: Invasive mussels causing massive ecological changes in Great Lakes

April 13, 2011
Contact: Jim Erickson, (734) 647-1842, ericksn at umich.edu 
<http://ericksn@umich.edu>


_EDITORS_: Images are available at: 
http://ns.umich.edu/index.html?Releases/2011/Apr11/greatlakes


*Invasive mussels causing massive ecological changes in Great Lakes*


ANN ARBOR, Mich.---The ongoing spread of non-native mussels in the Great 
Lakes has caused "massive, ecosystem-wide changes" throughout lakes 
Michigan and Huron, two of the planet's largest freshwater lakes, 
according to a new University of Michigan-led study.

The blitzkrieg advance of two closely related species of mussels---the 
zebra and quagga---is stripping the lakes of their life-supporting 
algae, resulting in a remarkable ecological transformation and 
threatening the multibillion-dollar U.S. commercial and recreational 
Great Lakes fisheries.

Previous studies have linked the mussels to far-reaching changes in Lake 
Michigan's southern basin. Now a paper by two University of Michigan 
ecologists and a colleague shows that the same dramatic changes are 
occurring in northern Lake Michigan and throughout Lake Huron, as well.

"These are astounding changes, a tremendous shifting of the very base of 
the food web in those lakes into a state that has not been seen in the 
recorded history of the lakes," said Mary Anne Evans, lead author of a 
paper scheduled for publication in the April 15 edition of the journal 
Environmental Science & Technology. "We're talking about massive, 
ecosystem-wide changes."

Evans is a research fellow at the U-M School of Natural Resources and 
Environment. The other authors are Donald Scavia, director of U-M's 
Graham Environmental Sustainability Institute, and Gary Fahnenstiel, 
senior ecologist at the National Oceanic and Atmospheric 
Administration's Great Lakes Environmental Research Laboratory.

Because the changes are so profound and are happening so rapidly, the 
authors recommend that Great Lakes management agencies review and 
perhaps revise their policies so they can respond more quickly.

"New strategies for managing the lakes are urgently needed. Ecological 
changes that formerly occurred over decades are now happening in just a 
few years, so we need to adapt our management policies to this new 
reality," Scavia said.

This recommendation is especially relevant in the context of the current 
review of the Great Lakes Water Quality Agreement by the International 
Joint Commission, Scavia said. Through the IJC, the United States and 
Canada jointly manage the Great Lakes.

Though the zebra mussel is better known to the public, over the past 
decade it has largely been overshadowed by the quagga mussel, which can 
thrive far from shore in deep, mud-bottomed waters. Each of the 
fingernail-size quagga mussels filter about a quart of water a day, and 
billions of them now blanket the bottoms of lakes Michigan and Huron 
down to depths of nearly 400 feet.

They feed on algae, including single-celled plants called diatoms that 
are encased in glass-like shells made of silica, which the diatoms 
extract from lake water. Until recently, the diatoms "bloomed" each 
spring in the Great Lakes, and the level of silica in upper lake waters 
dropped as diatoms built their protective shells, then sank to the lake 
bottom, taking the silica with them.

The drop in silica levels due to the spring diatom bloom, known as the 
seasonal drawdown, has long been used as an indicator of overall algal 
production in the Great Lakes.

Reviewing records of silica levels in lakes Michigan and Huron collected 
over the past 30 years by the Environmental Protection Agency, Evans and 
her colleagues found that algal production throughout the two lakes was 
about 80 percent lower in 2008 than it had been in the 1980s.

In Lake Michigan, the decrease in the seasonal drawdown coincided with 
an explosion in the quagga mussel population and its expansion to 
greater depths, which began in 2004. The same changes occurred a few 
years earlier in Lake Huron, where quagga mussels greatly increased in 
abundance between 2000 and 2003.

"For years, all the talk was about the zebra mussels. And then its close 
cousin comes in, the little quagga mussel, and wreaks even more havoc on 
these huge offshore systems," said NOAA's Fahnenstiel.

"These changes are unprecedented," he said. "In terms of algal abundance 
and water clarity, lakes Michigan and Huron are now similar to Lake 
Superior."

By filtering out the algae, the mussels are robbing other organisms of 
the food they need to survive. Of particular concern is the plight of 
Diporeia, a tiny shrimplike creature that was one of the pillars 
supporting the base of the Great Lakes food web.

Nearly every fish species in the Great Lakes relies on Diporeia at some 
point in its life cycle. But Diporiea populations have crashed in lakes 
Michigan and Huron, and the change is already impacting Great Lakes 
commercial fisheries and the sport-fishing enterprise.

"The big question now is how large the quagga mussel population will 
get," Evans said. "And when it gets as big as it can get, will it stay 
at that level or will it die back because it has decimated its own food 
supply? We don't really know what to expect at this point."

More information:

Read the Environmental Science & Technology paper: 
http://pubs.acs.org/doi/abs/10.1021/es103892w

U-M School of Natural Resources and Environment: http://www.snre.umich.edu

U-M Graham Environmental Sustainability Institute: 
http://www.graham.umich.edu/

NOAA's Great Lakes Environmental Research Laboratory: 
http://www.glerl.noaa.gov/

U-M Sustainability fosters a more sustainable world through 
collaborations across campus and beyond aimed at educating students, 
generating new knowledge, and minimizing our environmental footprint. 
Learn more at: sustainability.umich.edu <http://sustainability.umich.edu>

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[lakes3]

-- 
Jim Erickson
News Service
University of Michigan
412 Maynard
Ann Arbor, MI 48109-1399
Direct: 734-647-1842
Main: 734-764-7260
Fax: 734-764-7084
Office web: http://www.umich.edu/news

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