Evaluating Influence of Temperature and Phosphorus on E. Coli Growth

The 13 public Lake Erie beaches of Presque Isle State Park have been particularly affected by water pollution. In 1991, Presque Isle Bay was designated as the 43rd Great Lakes Area of Concern by the U.S. Department of State. While the bay has now been listed as an Area of Recovery, bacterial contamination of the lake‐side beach waters is still present, resulting in anywhere from five to an excess of forty beach action notifications annually, posing a recurring health risk to park guests swimming in these waters. As part of previously funded Pennsylvania Sea Grant initiatives, we have determined that the nuisance algae Cladophora can harbor very high levels of E. coli. This can pose a serious health risk to recreational swimmers who might come into direct contact with this algae. Also, Cladophora can serve as a source of E. coli contamination to the beach waters in which it resides, thereby indirectly putting beachgoers at risk of getting ill and contributing to the beach closings observed at Presque Isle State Park. Previous monitoring efforts by many laboratories have identified phosphorus levels and water temperature as the two main factors that mitigate Cladophora abundance in Great Lakes beach waters. While temperature and phosphorus concentration might promote high levels of Cladophora in beach waters on certain days, the role that these variables have in mediating E. coli abundance on the Cladophora has yet to be determined in Presque Isle, or other, Great Lakes beach waters. Thus, determination of the health risk that Cladophora has in recreational waters on any given day, irrespective of Cladophora abundance, remains unknown. To fully understand how E. coli concentration on Cladophora relates to Cladophora abundance, we undertook a series of experiments that tested E. coli concentration under different temperature and phosphorus concentration under both laboratory and environmental conditions in the beach waters of Presque Isle State Park.  Overall Findings

• Under laboratory conditions, the optimal temperature for E. coli growth on Cladophora is 44.5°C.
• Under laboratory conditions, the optimal concentration of phosphorus for E. coli growth on Cladophora is 100mM.
• There was no clear evidence that water temperature in Presque Isle beaches related to E. coli concentration on the Cladophora present in that water.
• There was no clear evidence that phosphorus concentration in Presque Isle beach water related to E. coli concentration on the Cladophora present in that water.
• Other factors besides water temperature and phosphorus concentration act to mediate E. coli concentration on Cladophora in freshwater.

 Recommendations

• Since factors that determine overall Cladophora abundance in freshwater (ie‐ water temperature and phosphorus loading) do not relate to E. coli concentration on Cladophora, beach management decisions should not be made using the overall abundance of Cladophora as an indicator.
• Further work is needed to understand what variables besides water temperature and phosphorus loads influence E. coli concentration on Cladophora in freshwater.
• Examination of how water temperature, phosphorus loading, or other variables impact the concentration of specific pathogenic bacterial types in water or Cladophora will yield more specific insight into water quality to make beach management decisions.