Aliens invade the Great Lakes
The ecology of the Great Lakes may be permanently altered by invasive species of mollusks that filter out algae and diatoms needed by native species. There appears little that can be done.
Tuesday, July 21, 2009
by Jim Erickson
Abroad the research vessel Laurentian on Lake Michigan, the steel cable whines and the winch groans as it hoists a net crammed with about 300 pounds of fingernail-size quagga mussels over the stern and onto the deck.
University of Michigan fishery biologist David Jude opens the net and starts sorting the catch, the result of a five-minute trawl along the bottom of Lake Michigan, about 3½ miles west of Grand Haven in the lake's southern basin.
Tiny shrimp-like creatures called diporeia also eat diatoms. Their numbers have declined sharply in recent years, and scientists suspect it's because the mussels are filtering diporeia's food from the water. As a result of the diporeia's population crash, "prey fish" such as alewives, which feed on diporeia, have also been declining.