Steven Verburg: Farm Pollution Exacerbated by Zebra Mussels

Wisconsin State Journal:

An explosion of the zebra mussel population in Lake Mendota this year could mean more foul-smelling shoreline slime and repeats of the major fish kill and vast bloom of toxic bacteria that hit Madison’s lakes already this summer, experts say.

Farm pollution is the main driver of this month’s surprisingly severe water quality woes, but the invasive mollusks now covering much of Lake Mendota’s bottom aren’t going to help matters.

“We’ve been shocked to see how many there are,” said Jake Vander Zanden, UW-Madison’s top expert on zebra mussels.

Zebra mussels change a lake by filtering food from water, which makes water clearer so that additional sunlight reaches the bottom. The sunlight, along with nutrients mussels excrete on the bottom, spur plant growth and the potential for more dead vegetation washing up and decomposing in smelly piles on shores, Vander Zanden said.

This year divers are finding a typical zebra mussel by-product — bottom-clinging mats of algae that look like green cotton candy — all over Lake Mendota, he said.