Keep cool at local pools, but beware E. coli and algae

Doggy paddlers beware: Lake MacBride has reported unusually high levels of E. coli this summer -- photo by Dawn Frary
Doggy paddlers beware: Lake MacBride has reported unusually high levels of E. coli this summer —photo by Dawn Frary

Johnson County beach bums and pool-goers hoping to beat the heat in the last days of summer should be wary of the microscopic company they keep.

“August is the peak month for the blue-green algae blooms that are an increasingly common threat to Iowa Lakes during the summer,” The Press-Citizen reports.

Caused in part by sewage runoff, agricultural fertilizer and other nitrogen and phosphorous-bearing sources, these algal blooms tend to carry microcystin, a toxin that can yield a nasty rash and induce vomiting in humans, and lead to potentially fatal liver damage in small animals. (Read: keep Fido out of the water).

E. coli, meanwhile, has a pronounced presence in several Johnson County lakes and public pools. Though the effects of the bacteria (commonly associated with fecal coliform) are mitigated by the chlorine in public pools, lakes have no such sterilizing protection. Lake MacBride, in particular, has had particularly high bacteria levels this summer.

Swimmers are advised to wash immediately after swimming and, of course, to refrain from swallowing pool and lake water.


  1. The high E. coli measurements at Lake MacBride seem to stem from all of the goose droppings on the beach, the location of the published results. Readings out in the lake, away from that area, are minimal. The iCows (Iowa City Open Water Swimmers) have been swimming the lake all summer without any illness attributable to the lake.

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