Biologist Jim Stoeckel holds glass plates covered with zebra mussels. The invasive species is dominating waterways in much of the Great Lakes region, but recently disappeared from the lower Illinois River.
Zebra mussels have been a problem in the Great Lakes region for morethan a decade. The fingernail sized invasive species has threatenednative plant and animal populations. It has also wreaked havoc withwaterfront industries and commercial fishing. But the pest has recentlydisappeared from one of the main rivers in the region. The Great LakesRadio Consortium’s Jonathan Ahl reports scientists are trying to figureout why:
Transcript
Zebra Mussels have been a problem in the Great Lakes region more than
a decade. The fingernail sized invasive species has threatened native
plant and animal populations. It’s also wreaked havoc with waterfront
industries and commercial fishing. But the pest has recently disappeared
from one of the main rivers in the region. The Great Lakes Radio
Consortium’s Jonathan Ahl reports scientists are trying to figure out why:
(Ambient sound of the river)
It’s a cool summer morning on the banks of the Illinois River near
Havana. Water is gently washing up against a pile of rocks on this bend of
the river half way between St. Louis and Chicago. Just a few years ago,
these rocks were covered with Zebra Mussels. The bottom of the Illinois
River had a six inch deep carpet of the invasive species when they were at
their peak in the early nineties. But now there are only a few Zebra
Mussels stuck to these smooth rocks. Bob Williamson is the Director of
Commercial Fishing for the Illinois Department of Natural resources. He
says fishermen on the lower Illinois river stopped complaining about Zebra
mussels about a year ago:
“Prior to that if they put a net down for any
period of time, or any kind of gear or a boat or anything in the water, they
would be encrusted with these things. And I was getting reports from
everyone that it wasn’t happening anymore, that they weren’t seeing them.”
Williamson says he canvassed a twenty mile stretch of the river and only
found three live Zebra mussels. He says he was surprised by the results,
and doesn’t know why it happened. Researchers are trying to find out.
(Ambient sound in the lab)
Biologist Jim Stoeckel is working in his lab at the Havana Field Station.
It’s a weekend, but he came to work to check on the Zebra mussels housed in
two dozen aquariums in the less than spacious room at the state run
facility. Stoeckel is running tests to find out what could be reducing the
Zebra mussels population on the lower Illinois River. Stoeckel says so far
the research seems to be pointing at the large amount of sediment in the
river. He says since Zebra mussels eat by filtering food from flowing
water, a large amount of dirt and silt makes it very hard for them to eat:
“So they have to expend, in some cases have to
expend more energy separating out the food particles from the non food
particles. And that can result in a lower growth rate, or even death.”
Stoeckel says the warmer water temperatures in the Illinois may also be
adding to the disappearance of the Zebra mussels. Pat Charlebois is a
biologist with the Illinois-Indiana Sea Grant. She says if those
preliminary results hold up. the findings are troubling. That’s because if
sediment is the reason for the disappearance of the Zebra Mussel, then the
river has bigger problems than an invasive species.
“Some people may see it as we are controlling
Zebra mussels in this way, but that is not a final solution for the control
of Zebra mussels to heat up the water and add sediment. I don’t think most
people would look at that as a final solution.”
She says the discovery may lead to a better understanding of the invasive
species, but it doesn’t lead to a quick fix to the problem. Biologist Jim
Stoeckel agrees. He says sediment is also hurting native plants and animals
in the river, and is a much bigger problem than a proliferation of an
invasive species.
“So in the overall picture, it would be much
better to clean up the suspended solids problem and perhaps deal with higher
populations of Zebra Mussels in the future.”
Stoeckel says discovering relationship between sedimentation and lower
Zebra Mussel populations is, at best, a mixed bag. He says he wants to
continue his research on to see if a better understanding of these pests may
lead to a practical way to control the Zebra Mussel. For the Great Lakes
Radio Consortium, I’m Jonathan Ahl.