A swim advisory for microcystins has expired at Lake Macbride, as the toxins from harmful algae were killed off by summer sunshine earlier this week.
But don’t get too excited. Water testing Tuesday at Lake Macbride showed elevated levels of E. coli bacteria, a more common problem park managers believe is connected to goose feces near the beach.
Lake Macbride is one of 39 state park beaches that gets weekly water monitoring for E. coli bacteria and microcystins. E. coli is an indicator of fecal material, which can carry parasites or other pathogens that can sicken swimmers. Microcystins, generated when blue-green algae die, can cause gastroenteritis, skin irritation, liver damage and nerve damage.
Lake Macbride, a 940-acre lake with a maximum depth of 45 feet, developed a harmful algal bloom in mid-June, Park Manager Ron Puettmann said earlier this week.
Water tests on June 18 at the Lake Macbride beach showed microcystin levels were 22.26 micrograms per liter of water, above the 20 micrograms-per-liter standard the Iowa Department of Natural Resources uses for recreational waters. The Iowa DNR posted a microcystin swim advisory June 21 — the first ever for Lake Macbride, the DNR reported.
The algae bloom turned the lake a murky green for the weekend of June 22-23, but by Thursday the water appeared visibly clearer. Lake water quality can vary widely depending on rain events, which can wash fertilizer, manure or goose feces, into the water.
Macbride had E. coli bacteria advisories 12 of 15 weeks last summer.
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