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Aquatic Exotics: Highlights of the Ninth International Zebra Mussel and Aquatic Nuisance Species Conference

Dr. William Brown

Dr. William Brown, Science Advisor to the Secretary of the Interior, was a keynote speaker for this year’s International Zebra Mussel and Aquatic Nuisance Species Conference.

Over 400 people attended the Ninth International Zebra Mussel and Aquatic Nuisance Species Conference in Duluth, MN, April 26-30. Minnesota Sea Grant hosted this exchange of discoveries and ideas that attracted scientists from around the world.

Discussions ranged from ballast water management to the biological control of aquatic pests. The lack of domestic and global plans preventing the spread of aquatic organisms concerned participants, including keynote speaker Dr. William Brown, Science Advisor to the Secretary of the Interior. In an effort to address this, the Aquatic Nuisance Species Task Force passed a ballast water resolution during their meeting held in conjunction with the conference (see news release below).

Some of the 190 research projects presented are described below.

Mussel Populations Growing in Duluth-Superior Harbor

The zebra mussel infestation in Duluth-Superior’s harbor is expanding, according to Mary Balcer, chair of the Biology Department at the University of Wisconsin-Superior. Balcer attributes the expansion to unusually warm temperatures over the past two years. Although zebra mussels have lived in the harbor for a decade, Lake Superior’s cold water, long winters, lack of food, and low dissolved calcium levels inhibited their growth and reproduction. Formerly, only about 100 zebra mussels occupied a square meter in a few locations and only 15-54 percent of the population managed to survive winter. Last September, however, Balcer found over 5,000 zebra mussels covering a square meter. Even more foreboding was her discovery that 75-100 percent of the mussels survived last winter and they were robust enough to reproduce. This could mean trouble for industries that have water intakes in the harbor (zebra mussels can attach to water intakes and block them). More reproducing mussels also increases the chance for accidental introductions into other lakes by boat owners and anglers who use the harbor and then travel.

Too Hot for Mussels

Lorenzo Torres (MEDD4) and his colleagues discovered that zebra mussels don’t like spiced paint. The researchers developed a way to molecularly bond the terpenes of chile peppers to paints, plastics, and stains. Terpenes are the pungent active ingredient in peppers - what makes them “hot.” The bonded chile terpenes repel bio-fouling species and appear to last long enough to be commercially-viable. Juvenile zebra mussels avoided experimental materials submerged in Lake Michigan although some adult mussels attached to moderately “hot” surfaces. Mussels completely avoided the “hottest” surfaces.

“Fish and snails seem to live normally around treated materials,” Torres said. Torres and his colleagues will continue to test their spicy product with the aim of offering it commercially as a non-poisonous anti-fouling agent.

Zebra Mussel Filters

Richard Steffen, Assistant Professor of Plant, Soil, and General Agriculture with the Southern Illinois University, approached zebra mussels from an applied angle; he used them to filter suspended particles from swine effluent. His research demonstrated that passing pre-filtered wastewater through a bed of zebra mussels significantly reduced turbidity and chemical oxygen demand, and also positively affected ammonia, nitrogen, phosphorus, and pH levels. Steffen thinks zebra mussels could eventually become part of a closed-loop system, where water cycles back into hog pens.

“The zebra mussel’s ability to clear water is well documented,” said Steffen. “Now we’re trying to apply it.”

Luring Lamprey

Peter Sorensen, Professor of Fisheries and Wildlife with the University of Minnesota, isolated two bile acids unique to lamprey larvae. These bile acids attract adult lamprey, whose chemo/pheromone receptors are extremely well-developed. In effect, their noses are bigger than their brains. Sorensen found that adult lamprey detect the bile acids in concentrations as low as 100 parts per trillion and select spawning streams based on larval odors. Sorensen intends to conduct field trials using the bile acids to lure lamprey into traps. He also plans to develop bile acid detectors to census lamprey larvae in streams.

“The lamprey’s pheromone sensitivity is the weak link in its physiology,” Sorensen said. Given that one “swimming nose” can kill 40 pounds worth of fish and alternative controls rely on toxicants, Sorensen’s research promises to evolve into an important way to help manage lamprey.

Ruffe’s Delayed Impact

Only about 15 years have passed since Eurasian ruffe arrived in the Duluth-Superior harbor but recent bottom trawls indicate they constitute an estimated 80 percent of fish abundance. Jeffrey Schuldt, Research Associate with the Natural Resources Research Institute, examined the effect that this ruffe explosion might have on yellow perch and the harbor’s aquatic ecosystem. Schuldt’s enclosure experiments showed that within five weeks perch living with ruffe had grown more slowly than perch living with other perch. After five weeks the macroinvertebrate community had changed, indicating that perch and ruffe compete through resource depletion and interference.

“When ruffe and perch rely on the same resources, ruffe are able to consume more of the food, resulting in slower-growing perch. Smaller perch lay fewer eggs and are more vulnerable to predation. The interaction between ruffe and yellow perch is subtle, so it may take years before we can detect a decline in the perch population,” Schuldt said.

Great Lakes Ballast Technology Demonstration Project Discoveries

The Great Lakes Ballast Technology Demonstration Project results are leading to bigger ideas. In cooperation with numerous institutions, researchers studied how efficient and effective backwash filters were in removing organisms from ballast water. They found that a 50 micron filter backwashes about 10 percent of the time whereas a 25 micron filter was in a backwash cycle most, if not all, of its operating time. Surprisingly, 50 micron mesh removed more debris than 25 micron mesh; the smaller mesh tended to break up larger particles. The 25 micron and 50 micron meshes removed almost all of the zooplankton in a sample but the 50 micron mesh was less effective at removing phytoplankton, which are generally smaller than zooplankton. Viruses and bacteria are so miniscule (under 10 microns) that even the 25 micron filter failed to remove them. Project cooperators are now exploring secondary treatments and encouraging engineers to design blueprints for shipboard ballast water filters.

Beyond Science

The sense of urgency that attracted conference attendees also attracted national attention. Scientists and policy-makers publicly supported recent federal initiatives combating the spread of exotics. Even Voice of America, a world wide radio program that is translated into 52 languages and has 80 million listeners, helped spread aquatic nuisance species news. To encourage awareness, conference organizers included a media briefing, youth poster contest and workshop, and public symposium on invasive aquatic species for lake association members and lakeshore property owners.

Fisheries and Oceans Canada will host the Tenth International Aquatic Nuisance Species and Zebra Mussel Conference in Toronto, Ontario, February 14-18, 2000. For more information contact conference administrator Elizabeth Muckle-Jeffs at 1-800-868-8776 or by e-mail.

A limited number of conference abstract books are available from Minnesota Sea Grant for $10. Look on the publications page and our mail order form, under exotics, item X 60.

Alien Aquatic Species Will Be Turned Away At U.S. Borders

News Release from the Aquatic Nuisance Species Task Force

In an effort to reduce the devastation from aquatic nuisance species to the ecology, economy, and health of the nation’s coastal environment, the Aquatic Nuisance Species Task Force passed a resolution on April 30 to accelerate its efforts to eliminate invasive species that enter U.S. harbors through ballast water pumped from ships.

The task force, meeting in conjunction with the Ninth International Zebra Mussel and Aquatic Nuisance Species Conference, agreed to a resolution that:

  1. COMMITS to eliminate, as soon as possible, ships’ ballast water as a significant pathway for the introduction of invasive species into American waters;
  2. SUPPORTS ongoing domestic and international efforts to develop a comprehensive, effective, and consistent suite of guidance and authorities that will reduce the risk of transfer of aquatic nuisance species through ships’ ballast water;
  3. PLEDGES to support further research and development efforts to find a simple, effective and safe method for ballast water management;
  4. SEEKS to collaborate actively with maritime interests and other industry representatives to ensure that a workable, safe, and environmentally sound solution to this crucial problem is found as soon as possible; and
  5. FURTHER SEEKS to enhance cooperation and coordination among federal, state and tribal governments to maximize the effectiveness in eliminating the transfer of aquatic nuisance species through ships’ ballast water as a source of future introductions into the waters of the United States.

“We are at critical mass in the fight to control the impact of alien aquatic species. We must act aggressively to stem the tide of these invaders,” said Sally Yozell, deputy assistant secretary for oceans and atmosphere at the U.S. Department of Commerce. “Every minute 40,000 gallons of foreign ballast water is dumped into U.S. harbors. This water contains a multitude of stowaways that could alter or destroy America’s natural ecosystems and severely harm the coastal economies they support.”

“Eliminating ballast water as a major pathway for introducing invasive species into aquatic ecosystems will require a concerted and committed effort by all involved,” said Gary Edwards, assistant director for Fisheries, National Fish and Wildlife Service.

The task force is an intergovernmental organization dedicated to preventing and controlling aquatic nuisance species, and implementing the Nonindigenous Aquatic Nuisance Prevention and Control Act of 1990. The task force, co-chaired by the U.S. Fish and Wildlife Service and National Oceanic and Atmospheric Administration, was established to coordinate governmental efforts related to nonindigenous aquatic species in the United States.


During the conference, Congressman James Oberstar and the Aquatic Nuisance Species Task Force presented awards honoring the exceptional ballast water research of Dr. James Carlton (Director of the Maritime Studies Program and Professor of Marine Sciences at Williams College, CT) and the leading role the Northeast-Midwest Institute (Washington, D. C.) assumed in promoting reauthorization of the National Invasive Species Act (NISA) of 1996, and in initiating the Great Lakes Ballast Technology Demonstration Project. The task force also honored Jay Rendall (Minnesota Department of Natural Resources, St. Paul) for helping name NISA.

Oberstar also presented the following winners of the youth poster contest with a certificate.


“Clean Your Boat,” by Laura Kleinke of East High School, Duluth, Minnesota, won an award of excellence.

Award of Excellence

4th and 5th Grades

Beau Grotberg and Eric Young, Birchwood

Middle School

Tina Driscoll, Two Harbors

High School

Laura Kleinke, East

People’s Choice Award

6th Grade

Joshua Ruiz, Northwoods School, Duluth

Award of Distinction

4th and 5th Grades

Megan Rempkowski, Washington Elementary, Cloquet

Middle School

Blake Parnin, Cloquet

High School

Kristi Ostrowski, East

By Sharon Moen
September 1999

Return to September 1999 Seiche

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