[Date Prev][Date Next][Date Index]
GLIN==> News Release: E. coli as Indicator of Beach Contamination
- Subject: GLIN==> News Release: E. coli as Indicator of Beach Contamination
- From: "Marie E. Zhuikov" <email@example.com>
- Date: Tue, 12 Jun 2007 14:21:15 -0500
- Delivered-to: firstname.lastname@example.org
- Delivered-to: email@example.com
- List-name: GLIN-Announce
Note: Background info. follows after (below) the news release.
MN SEA GRANT
Contact: Michael Sadowsky, (612) 624-2706, firstname.lastname@example.org, or
Randall Hicks, (218) 726-8438, email@example.com
Lake Superior Studies Point Out Problems With Using E. coli as an
Indictor of Beach Contamination
In three recent peer-reviewed journal articles, researchers from the
University of Minnesota provide evidence that the bacteria used to
justify beach closings don't always come from harmful sources.
Together, the papers add to mounting evidence that Escherichia coli (E.
coli) bacteria live as natural residents of the beach environment.
"Our results indicate that E. coli comes from several sources and may
survive and replicate in sand, sediment, soils, and algae in the
water," said Michael Sadowsky, professor at the University of
Minnesota, Twin Cities. "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 assumed that E. coli
found during beach monitoring is washed into the water from the land or
comes from sewage overflows, and we've shown that's not always the
E. coli bacteria typically live in the intestines of warm-blooded
animals (including humans and birds) and are used at most Great Lakes
coastal beaches as an indicator for pollution and an increased risk for
illness. While many strains are harmless, some cause gastrointestinal
illnesses in humans. Symptoms include vomiting, diarrhea, or other more
serious conditions. It's not clear, however, if the E. coli the
researchers found living in and around the beach cause any harm to
The papers were based on data collected from 2003 to 2005 in studies
funded by the University of Minnesota Sea Grant Program.
"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 Minnesota, Duluth. "It's
all a question of risk . . . what's the relative risk of an indicator
organism coming from a bird, versus a human, versus the sand."
Recently, health officials in Pennsylvania announced that beaches at
Presque Isle State Park on Lake Erie will no longer close due to
standard advisory levels of E. coli (235 colonies per 1,000
milliliters). The park revised its advisory system based on new health
risk information and allows up to four times the amount of E. coli
(1,000 colonies per 1,000 milliliters) as previously permitted for
The major findings of each paper are summarized below. Images of the
beaches and algae examined, and copies of the research papers are
available upon request from the researchers.
1) Ishii, S., W. B. Ksoll, R. E. Hicks, and M. J. Sadowsky. 2006.
Presence and growth of naturalized Escherichia coli in temperate soils
from Lake Superior watersheds. Applied and Environmental Microbiology
The researchers found that strains of E. coli from soil near streams
that enter Lake Superior were unique, suggesting that these strains
became naturalized to the soil. They also observed seasonal variations
in density of the soil E. coli. They found the greatest population
densities in June to October and the lowest numbers during February to
May. DNA fingerprint analyses indicates that the E. coli strains
survive the winter in frozen soil, increase in numbers in the spring
and summer, and are present over time. This is the first report of
growth of naturalized E. coli in natural (nonsterile, nonamended)
soils. The presence of these large populations of naturalized E. coli
in northern soils, which erode into streams or lakes and get into
waterways, may confound the use of this bacterium as an indicator of
2) Ishii, S., D. L. Hansen, R. E. Hicks, and M. J. Sadowsky. 2007.
Beach sand and sediments are temporal sinks and sources of Escherichia
coli in Lake Superior. Environmental Science and Technology
Researchers identified potential sources of E. coli in water, sediment,
and beach sand at the Duluth Boat Club Beach, located on the
Duluth-Superior Harbor, from spring to fall (April to October) in 2004
and 2005. E. coli counts increased during the summer and early fall
(July to September). They found that in spring (April and May), E. coli
likely originated from wastewater, while in early summer to fall (June
to October), waterfowl became the primary source of E. coli at this
beach. Less than 1 percent of the E. coli strains isolated from this
beach were potentially pathogenic. These results indicate E. coli from
humans and waterfowl can accumulate in beach sand and sediment, which
serve as temporal sources and sinks of E. coli that contribute to the
closure of this beach.
3) Ksoll, W. B., S. Ishii, M. J. Sadowsky, and R. E. Hicks. 2007.
Presence and sources of fecal coliform bacteria in epilithic periphyton
communities of Lake Superior. Applied and Environmental Microbiology
73(12): in press.
Fecal coliforms and E. coli were found in epilithic periphyton (i.e.,
the slimy algal layer covering rocks) at three beaches in Lake Superior
and the Duluth-Superior Harbor, including the Duluth Boat Club Beach.
The source of 2 percent to 44 percent of the E. coli isolated from
periphyton during 2004 and 2005 could be identified, with waterfowl
being the major source of E. coli in these periphyton communities. The
primary potential sources for most E. coli (57 percent to 81 percent)
in overlying waters at these beaches were waterfowl, periphyton, and
wastewater. Although many of the E. coli isolated from periphyton
originated from waterfowl and to a lesser extent from wastewater, other
strains appeared to be unique to the periphyton and may have developed
self-sustaining naturalized populations in these communities. E. coli
attached to periphyton can detach and contribute to fecal coliform
numbers measured in coastal waters. The presence, persistence, and
possible naturalization of E. coli in periphyton communities further
confounds the use of fecal coliforms as a reliable indicator of recent
fecal contamination of recreational waters.
Dr. Michael Sadowsky is a McKnight Distinguished University Professor
in the Department of Soil, Water, and Climate at the University of
Minnesota, Twin Cities. Dr. Randall Hicks is a Professor in the
Department of Biology at the University of Minnesota, Duluth. Satoshi
Ishii is a Ph.D. degree candidate in the Soil Science Graduate Program
at the University of Minnesota, Twin Cities. Winfried Ksoll received an
M.S. degree in 2006 from the Water Resources Science Graduate Program
at the University of Minnesota, Twin Cities. Dennis Hansen is an M.S.
degree candidate in the Biology Graduate Program at the University of
The researchers are completing examinations of potential sources of E.
coli in water, sediment, and sand at two other beaches sampled during
2006 in the Duluth-Superior Harbor, Southworth Marsh, and the Blatnik
Bridge Boat Landing. During summer 2007, Drs. Sadowsky and Hicks?
laboratories are starting a new two-year study to investigate the
short-term changes (days to weeks) in the abundances of waterfowl and
human-derived fecal bacteria at three Lake Superior beaches near
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
glin-announce is hosted by the Great Lakes Information Network (GLIN):
To subscribe: http://www.glin.net/forms/glin-announce_form.html
To post a message: http://www.glin.net/forms/glin-announce_post.html
To search the archive: http://www.glin.net/lists/glin-announce/
All views and opinions presented above are solely those of the author or
attributed source and do not necessarily reflect those of GLIN or its
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *