Picture a giant factory filled with thousands of machines. It’s an amazing factory, far more complex and efficient than anything man could envision, let alone construct. Each machine takes in material and energy and produces the perfect item to pass along the production line. The factory has evolved to this remarkable state over the course of thousands of years.

Now imagine that some of the machines in the line are removed and new machines take their places. But the new machines are not as efficient. Some produce things that the factory can’t use, like wrong size screws piling up on the floor. Or the new machines produce things that can be used, but don’t fit quite right. Pretty soon inefficiencies compound, the factory produces less, and what it produces is of less quality.

This metaphor reflects what’s happening in the Great Lakes in general and with diporeia and the invading zebra mussels and quagga mussels in particular. The diporeia does an amazing job of transferring food from the bottom of the lake to fish that swim above. But zebra mussels and quagga mussels filter tremendous amounts of food from the lake and make it far more difficult for other species — species not adapted to eating them — to access the food they contain. The food stays on the bottom of the lake, the direct opposite outcome of what diporeia achieve.

Jeff Smith is editor of Traverse, Northern Michigan’s Magazine.smith@traversemagazine.com

Note: This article was first published in August 2006 and was updated for the web February 2008.