R.L. Whitman M.N. Byappanahalli 2009 In recent years, massive avian die-offs from <i>Clostridium botulinum</i> type E infection have occurred in the Sleeping Bear Dunes National Lakeshore (SLBE) area of Lake Michigan. These outbreaks have been coincidental with massive blooms of the green algae <i>Cladophora</i>, mostly <i>Cladophora glomerata</i>. We tested the hypothesis that <i>Clostridium botulinum</i> type E can grow under suitable conditions in these algal mats. In a lab mesocosm study, <i>Cladophora</i> from four outbreak-impacted beaches from SLBE were compared with four unimpacted beaches in the Milwaukee–Racine area for <i>bontE</i> gene of <i>Clostridium botulinum</i>. Frequency of the <i>bontE</i> gene was higher after incubation (25 °C for up to 6 weeks) of <i>Cladophora</i> from impacted vs. the unimpacted area. Since no type E gene was detected initially in <i>Cladophora</i> from any of the eight locations, we infer that the increased occurrence of type E gene arose from spore germination or vegetative <i>Clostridium</i> growth within the existing algal mats of SLBE. Moreover, we found that the congener <i>Clostridium perfringens</i> readily grows in mesocosms containing <i>Cladophora</i>. application/pdf 10.1139/F09-052 en NRC Research Press <i>Clostridium botulinum</i> type E occurs and grows in the alga <i>Cladophora glomerata</i> article