Zebra mussels likely contributing to Great Lakes algae ills
Written by Star Tribune   
Saturday, 29 January 2005 06:39
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.

``Because it smells very similar to sewage, people mistakenly suspect that the decaying algae is caused by sewer overflows,'' she said.

The mussels are natives of Europe that were inadvertently transported to the Great Lakes in the bilge water of ocean-going ships. The algae occurs naturally in Wisconsin waters, growing on submerged rocks, logs or other hard surfaces and then coming loose and being washing ashore.

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

New research about the algae, options for cleaning it from beaches and future plans for monitoring and researching it are to be presented Feb. 18 at a public forum at Lakeshore Technical College in Cleveland, just north of Sheboygan.

Shaili Pfeiffer, a water resources specialist with the Department of Natural Resources, said the forum will give people a chance to learn about research conducted by various agencies and individuals last summer.

``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.

The public forum is being sponsored by the DNR, the UW Sea Grant Institute, UW Extension, and the Wisconsin Coastal Management program in the state Department of Administration, a primary funder of Cladophora-related research and outreach.

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