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Bacteria on the Beach

Heidi Bauman, coordinator of the Lake Superior Beach program, wades into shore at Park Point after taking a water sample.

Heidi Bauman, coordinator of the Lake Superior Beach Program, takes a water sample to monitor for bacteria. Last summer, ten Lake Superior beaches were posted with public health advisories. Photo: Duluth News Tribune

Duluth extends into Lake Superior on one of the largest freshwater sandbars in the world. Park Point, as itís known, is a spit of land that divides the busy harbor from Lake Superior. Ships come and go through a natural opening at the end of the sandbar, but most navigate the Duluth Ship Canal on the opposite end, an artificial opening dug by enterprising citizens in 1871. In summer, scores of tourists and locals alike cross the Aerial Lift Bridge to soak up the sun and sand. Park Point residents have the beach literally at their doorstep.

Twice a week last summer, beaches on Park Point and some along the North Shore of Lake Superior received other visitors - staff from the Minnesota Pollution Control Agency (MPCA) and local county health departments who were sampling water for a new program thatís part of a national effort to monitor swimming beaches and notify the public when water quality problems arise. They found occasional problems with bacteria that could impact public health, and a team of Sea Grant-funded researchers is helping pinpoint potential sources of these elevated levels.

In 2000, the Clean Water Act was amended to include significant beach protection provisions with the passage of the Beaches Environmental Assessment and Coastal Health (BEACH) Act. This law authorized national funding to assist state, tribal, and local governments in developing and implementing beach monitoring programs. It also required states to improve water quality standards for pathogens and pathogen indicators, and obligated the Environmental Protection Agency to improve microbiological water quality criteria guidance.

The MPCA received a grant from the BEACH Program in 2003 and conducted a pilot monitoring program in cooperation with local health and environmental officials. The agency monitored 35 beaches during the swimming season, from one week before Memorial Day through one week after Labor Day, using 235 Escherichia coli (E. coli) colonies and 400 fecal coliform colonies as trigger points for a "no water contact" advisory. When they found a contaminated beach, they posted an advisory, which in essence closed the beach. Of the monitored beaches, ten had public health advisories for a total of 58 days. The site with the most advisories (49 days) was on the harbor side of Park Point at the Duluth Boat Club Landing.

Heidi Bauman, coordinator of the Lake Superior Beach Program, suspects this could be due to the locationís warm dark water. Itís a convergent point for river and harbor currents, and is loaded with geese, ducks, gulls, and people walking dogs.

Because this was the first time area beaches had posted advisories, the monitoring program generated public attention. People wondered if higher-than-usual sewage overflows and human fecal material from incidents in 2003 caused the advisories. As it turns out, most of the advisories occurred without a known nearby sewage overflow, said Bauman.

Map of all Lake Superior beaches monitored for bacteria by the MPCA - Contact Minnesota Sea Grant for a listing of beaches

Lake Superior Beaches Monitored for Bacteria by the MPCA

Research Sheds Light on Sources of Beach Bacteria

Even with the beach public health advisories last year, there were no local reports of illness from beach swimming. Fecal coliformís presence doesnít necessarily mean public health is in imminent danger. Rather, it indicates that other more harmful bacteria could be present. E. coli is the most common fecal coliform bacterium.

Recent work by University of Minnesota researchers Mike Sadowsky and Randall Hicks indicates that the identified sources for most E. coli bacteria in six streams along the North Shore of Lake Superior, and a few samples taken from the harbor, were from birds and other wildlife.

They used a method called rep-PCR DNA fingerprinting to determine potential source animals contributing to the fecal pollution. They identified E. coli genetic "fingerprints" from specific animals to create a library for sample comparison. Their research staff sampled gulls and terns in the harbor and worked with local hunters and trappers to obtain samples from beaver and deer, for a total of 234 new isolates to add to Sadowsky's E. coli fingerprint library.

They then isolated E. coli from water samples and compared DNA fingerprints to the 1,765 patterns in the library. Preliminary studies done on a limited number of harbor samples indicated that only two of 100 colonies came from humans. In North Shore river samples, humans contributed between 0 and 9 percent of the total E. coli that could be identified. By contrast, E. coli from waterfowl and wildlife accounted for 56-97 percent of the total E.coli in the streams.

Sadowsky and Hicks hope to use their microbial sources tracking method to help identify the sources of E. coli bacteria found at beaches closed by the MPCA through future research projects. For more information, contact Michael Sadowsky at (612) 624-2706 or Randall Hicks at rhicks@d.umn.edu. Visit the Minnesota Lake Superior beach program Web site at www.pca.state.mn.us/water/beaches/.

By Marie Zhuikov
June 2004

Return to June 2004 Seiche

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