Water quality improves at formerly bacteria-laden Spirit Lake beach
The Iowa Department of Natural Resources monitors water quality at state beaches throughout the summer. (Photo courtesy of David Thoreson)
State officials have lifted a warning against swimming at a northwest Iowa beach now that large concentrations of toxins and bacteria in its water have waned.
Tests last week by the Iowa Department of Natural Resources showed unhealthy amounts of blue-green algae toxins at Crandall’s Beach at Spirit Lake, along with the highest concentration of E. coli bacteria the department has detected at state beaches this year.
New water sampling this week on Wednesday still showed elevated levels of the toxins, but they were slightly below the 8 parts per billion threshold at which the DNR issues a “swimming not recommended” warning.
The recent DNR tests show that bacteria concentrations have vastly diminished at the beach, from more than 24,000 viable bacteria per 100 milliliters of water to 52. The test last week was unable to precisely quantify the bacterial concentration because the water exceeded the test’s upper limit.
The area has been plagued by a large algae bloom — the primary source of the toxins and a potential source of food for E. coli — and recent rains had likely washed bacteria into the lake. The bacteria and toxins can cause skin irritations, illnesses and infections among people who come in contact with contaminated water.
Swimming is not currently recommended at nearby Emerson Bay Beach on West Okoboji Lake. Tests of that water on Wednesday showed a concentration of 1,800 bacteria per 100 milliliters, which exceeds the limit of 235 that can trigger beach warnings.
The DNR also lists swim warnings for the following beaches, all of which have had consistently high bacteria counts in the past five weeks: Backbone Beach in Delaware County; Big Creek Beach in Polk County; Brushy Creek Beach in Webster County; Lake Darling Beach in Washington County; Nine Eagles Beach in Decatur County; and Union Grove Beach in Tama County.
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