Zebra mussels making Lake Michigan look pretty clear
Written by Petosky News-Review   
Wednesday, 23 August 2006 14:54

Lake Michigan sure seems clear lately. While it has always been clear and beautiful to me, it just seems to be even more so now. I noticed this a couple of weeks ago as I sat on a boat watching a few friends swimming.

The water was as clear as freshly cleaned glass. One of the friends swimming around the boat, dove down, grabbed a rock and brought it to the surface to reveal the cause of the clear water - zebra mussels are filtering out the algae making the water clearer. The small, sharp invasive critters covered the rock.

The nonnative zebra mussel has invaded the Great Lakes and many inland lakes. But how did they get here? What are they doing? And what can be done about them?

It is believed zebra mussels came to the Great Lakes from Europe in the ballast water of ships. They were first discovered in Lake St. Clair in 1988.

While it may be hard to understand how the mussels got into a ship, you have to understand that they do not always appear in the shell form.


Before becoming the shells we have all come to know and hate, they spend time in a free-floating larval stage that is almost invisible to the human eye. This stage allows the organism the ability to spread throughout a lake or to other lakes with little detection.

After a few weeks as a free-floating larva, the mussel attaches itself to a stationary object, such as a rock, boat hull or factory intake pipe and grows a shell with a dark, striped pattern. In this stage of its life it generally only grows about an inch long. However, they tend to gather in clusters of sharp little shells that I hate walking on.

The zebra mussel eats algae by filtering it out of the water. This is where it creates problems for the environment and us.

By filtering algae out of large amounts of water, the mussels take away a type of food at the beginning of the food chain in an ecosystem. If you remember your high school biology, you know if one portion of a food chain is impacted in an ecosystem, this affects all of the other animals up the chain - from those that feed on the algae to those that feed on the animals that eat the algae and so on.
 
This means that wonderfully clear water we are enjoying a swim in is a disaster for the ecosystem.

In addition to the ecosystem impact, the mussels also impact our economy by costing many factories a lot of money. The mussels love to attach themselves to intake pipes at factories because flowing water into these pipes provide the mussels with plenty of food.

However, they gather in such large numbers that they can clog a pipe, forcing the company to spend a lot of money cleaning out the pipe or redesigning it.

So, what can we do about them? Scientist are studying this very issue. So far there are no chemicals that can be used on the zebra mussels in great amounts that will not impact the native wildlife around it. However, scientist are looking at other ways of controlling this nuisance, such as disrupting its reproductive process and the use of chlorine.

As far as nature's control of the species, there are not many predators that feed on them. Some diving ducks have been seen eating them - in fact, according to a report by Purdue University increasing numbers of migrating ducks are being noticed in western Lake Erie feeding on zebra mussels - and some fish will eat the larval stage of the mussel.

Human consumption is not recommended when it comes to these animals. While they are edible, and very small, the United States Department of the Interior points out because the animal filters water its meat can contain pollutants that are harmful to humans. I did look for recipes on the Web though, and did not come up with anything of value. So I, too, would suggest not eating them.

However, humans can have an impact on this animal simply by helping stop their spread.

Some suggestions are: Make sure your boat is clear of all zebra mussels before transporting it to another lake, do not catch zebra mussels for use as bait in other lakes and do not dump water from live wells and bait buckets in another body of water.

Perhaps someday the lake will not be as clear, but will be its healthy self again.

 
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