Zebra mussels likely suspects in Great Lakes algae ills

The Duluth News Tribune carries this article explaining zebra mussels and Great Lakes algae:

A rising tide of stringy, smelly algae on Great Lakes beaches in recent years likely results from zebra mussels creating clearer water while also adding nutrients to the lake bottom, researchers say. The algae, called Cladophora, may get even more blame that it deserves for the putrid smell, said Vicky Harris, a water quality and habitat restoration specialist for University of Wisconsin Sea Grant Institute. Zebra mussels often get tangled in the algae and washed up with it, and the decaying mussels are more pungent than the algae alone - although that smell is powerful enough to be highly offensive, she said.

A midsummer die-off of algae, possibly because of warming water, increases the amount of it that washes up and decays.

"Cladophora is a problem in all the Great Lakes except Lake Superior," Harris said. "We're not quite sure why this type of algae has made such a comeback from the former nuisance levels in the 1960s, but we know that the water is clearer and light is able to penetrate more deeply."

Harris said levels of nutrients such as phosphorus that led to algae growth in the past have dropped, but the water filtered by zebra mussels is so clear that sunlight can penetrate far deeper, allowing algae to grow at depths of 60 feet or more. Also, the mussels' waste provides bottom fertilizer for algae.