E. coli growing in Great Lakes beaches naturally, studies say
At least some of the E. coli bacteria closing Great Lakes beaches is growing there naturally and is not the result of sewage spills, gulls or pets.
That's the finding of Uni-versity of Minnesota research projects reported recently in three scientific journals. They echo a Michigan study re-ported in the News Tribune one year ago.
It was previously believed that E. coli could come only from the guts of warm-blooded animals, and that, if found in the environment, there must have been a recent source of excrement from one of those animals.
That's why E. coli is used as an indicator for other, more dangerous bacteria that could spread human diseases.
On Tuesday, the Minnesota Pollution Control Agency issued an advisory for the Duluth Boat Club harbor beach at 14th Street on Park Point because of high E. coli levels.
But if e-coli is naturally occurring in the sand, it may mean the bacteria doesn't represent any real danger in the water, or at least that it doesn't make for a great indi-cator of elevated risk of dis-ease. The recent studies also found E. coli in soil near streams.
"E. coli comes from sev-eral sources and may survive and replicate in sand, sedi-ment, soils and algae in the water,'' said Michael Sadowsky, professor at the University of Minnesota-Twin Cities, in a statement. "This could increase the bacteria counts found on beaches, especially if the counts are taken on windy days when the sediment and algae are churned up. Often it's as-sumed that E. coli found dur-ing beach monitoring is washed into the water from the land or comes from sew-age overflows, and we've shown that's not always the case.''
In June 2006, a Central Michigan University report published in the Journal of Great Lakes Research con-firmed that E. coli can live and thrive in beach sand without a warm-blooded host.
E. coli is even surviving winter in the sand and is reproducing and expanding in the summer with no new source, the Michigan and Minnesota studies found. It's not clear what the original source of the sand-dwelling bacteria was or even if there was an outside source.
Scientists can determine what animal E. coli comes from based on DNA.
Wind and waves free the bacteria from the sand and bring it in contact with peo-ple. Beach monitoring pro-grams then pick it up in water samples and post beaches as closed.
That's happening every summer now along the water-front of the Duluth-Superior harbor, where E. coli prob-lems are chronic and some waterfront areas remain posted most of the summer for people to stay away.
But at least one Great Lakes agency has opted to drop the beach warnings at lower E. coli levels because of the recent research showing it likely isn't harmful. Health officials in Pennsylvania announced that beaches at Presque Isle State Park on Lake Erie will no longer close at the standard advisory levels of E. coli - 235 colonies per 1,000 milliliters. The park won't close the beach until levels hit 1,000 colonies per 1,000 milliliters.
The advisory limits ha-ven't been raised in Minne-sota or Wisconsin.
Some researchers say a new indicator may be needed to reflect the true risk to people at local beaches.
"Understanding how E. coli survives and interacts in the environment can help change our interpretation of beach monitoring results,'' said Randall Hicks, professor at the University of Minne-sota Duluth. "It's all a ques-tion of risk ... what's the rela-tive risk of an indicator or-ganism coming from a bird, versus a human, versus the sand.''
In a 2004-2005 study of the Duluth Boat Club beach at 14th Street on the harbor side of Park Point, researchers found that spring E. Coli levels likely increased from human sources while, in the fall, waterfowl were the pri-mary source.
In another study, of tradi-tional sources of E. coli, wa-terfowl accounted for between 57 percent to 81 percent of the E. coli found on Lake Supe-rior-area beaches. In one study, less than 1 percent of the E. coli strains identified at a specific waterfront area were potentially disease-carrying.