'Dead spot' in Lake Erie is new sign of trouble

Lake Erie, one of the five Great Lakes and one of the nation's greatest natural resources is endangered yet again.
Over the last two decades, enormous strides have been made to bring the lake back from the brink of destruction from a variety of pollutants and nearly a century of neglect.
Now comes word that the lake may not be as healthy as it appears to those of us who are enjoying ourselves on its shores.
Researchers have found a low-oxygen "dead zone" in the central basin of the lake and they believe that zebra mussels may be causing it.
In less than 20 years since zebra mussels arrived in the Great Lakes in the ballast of ships from Europe, they have been a nuisance and a threat to the ecology.
They are so prolific and so efficient at filtering water that here has been a noticeable increase in the clarity of the water in the Great Lakes. That may sound like a good thing, but clarity reduces plankton, and many species of fish feed on plankton, especially when they are young.
A decline in the fish population was to be expected as the zebra mussels proliferated, but the dead zone indicates that the invading clams may be having an even more profound effect on the lake than had been feared.
Study begins
A team of scientists is spending a week aboard a federal research vessel, conducting experiments and gathering water and soil samples from the center of the lake.
It is there that high levels of phosphorus are believed to be behind a dead zone that occurs in the central basin of Lake Erie between spring and fall. Colder, more dense water stays at the bottom and cannot be replenished with oxygen by moving to the surface, creating a harsh environment.
The strongest theory behind the cause is that on the zebra mussel is changing the ecosystem of the lake
Not only are they removing the plankton that some fish feed upon, but the clearer water is allow algae to grow at deeper depths.
Once the scientists -- both American and Canadian teams are conducting studies -- issue their findings, the eight Great Lakes states and two Canadian provinces are going to have to form a course of action.
Certainly U.S. and Canadian federal assistance is going to be needed. But as in all things concerning the lakes, it is important for the states and provinces to remain in the forefront of the effort.
It is those states and provinces who depend on the lakes and who have the greatest incentive to protect them for future generations. It is a responsibility that they have taken seriously, at least in recent years. They are in the best position to continue work aggressively to defeat the natural and manmade enemies of the Great Lakes.