Cladophora promotes escherichia coli growth and contamination of recreational waters in Lake Michigan
File(s)
Date
2010-01-07Author
Vanden Heuvel, Amy L.
Advisor(s)
Kleinheinz, Gregory
Metadata
Show full item recordAbstract
In recent years, thick mats of the green alga, Cladophora, have washed onto
beaches along Lake Michigan. These mats become stranded on the shoreline, begin to
rot, and are malodorous. The rotting mats are a nuisance to recreational beach users and
shoreline property owners. Cladophora mats have the potential to harbor Escherichia
coli, which is used as an indicator of recent fecal contamination to determine beach
closures. Cladophora mats may allow bacteria to survive and replicate by providing
nutrients, elevated temperatures, and protection from UV light. Bacteria-laden mats
potentially increase bacterial concentrations in surrounding recreational waters. To test
this hypothesis, stranded sampled stranded Cladophora mats were sampled for E. coli at
two beaches along Lake Michigan in Door County, Wisconsin. Random and gradient
water samples were collected to determine E. coli concentrations in water underlying the
mat and in surrounding water. Algal samples were collected and washed to determine E.
coli concentrations attached to Cladophora. Since E. coli in recreational water should
correlate with increased concentrations of pathogenic bacteria (also found in fecal
material), pathogen concentrations in and attached to Cladophora mats were examined.
Standard microbial culture methods were used to identify and enumerate pathogens such
as Salmonella, Shigella, and Campylobacter.
Escherichia coli concentrations in water underlying mats were significantly
greater than surrounding water (p < 0.001). Below mat E. coli increased as the stranded
mats persisted at the beach swash zone. Water adjacent to Cladophora mats had lower E.
coli concentrations but surpassed EPA swimming criteria the majority of sampling days.
A significant positive association was found between E. coli concentrations attached to
Cladophora and in underlying water (p < 0.001). The attached E. coli likely acted as a
reservoir for populating water underlying the mat. Removal of Cladophora mats from
beach areas may improve aesthetic and microbial water quality at affected beaches. Fecal
bacterial pathogens, however, could not be detected by microbiological culture methods
either attached to mat biomass or in underlying water. These associations call into
question the efficacy of using E. coli as a recreational water quality indicator of fecal
contaminations.
Subject
Escherichia coli
E.coli.
Feces--Microbiology
Cladophora glomerata
Freshwater algae--Research
Algae--Wisconsin
Permanent Link
http://digital.library.wisc.edu/1793/46219Description
A Thesis Submitted In Partial Fulfillment of the Requirements For the Degree of Master of Science-Biology, Microbiology