The Grand River Dam Authority is reporting that its most recent monitoring of a confirmed blue green algae (BGA) bloom in Grand Lake’s Horse Creek shows that, while the bloom has decreased in size, its toxin levels have increased. Due to that, GRDA continues to advise the public to use extra precaution in this area of the lake as the bloom can concentrate as it is pushed by the wind and waves.

Most recent testing by the GRDA Ecosystems and Watershed Management Department shows the Horse Creek bloom varying in toxin levels from 17 micrograms per liter (ug/l) to 8 ug/l. Environmental Protection Agency (EPA) guidelines, published in 2019, recommend no primary body contact with the water when microcystin concentration produced by the BGA is greater than eight micrograms per liter (>8ug/l).

At this time, GRDA’s ongoing monitoring suggests that the Horse Creek Bloom is the primary area of concern and GRDA will continue to monitor for additional blooms throughout the lake.

“Again, we want the public to be aware that the overwhelming majority of Grand Lake does not show any signs of BGA and is ready for visitors to come and enjoy,” said GRDA Vice President of Corporate Communications Justin Alberty. “However, we are continuing with our daily testing and surveys all across the lake because conditions can change rapidly.”

BGA may resemble thick pea soup, green paint or bluish, brownish, or reddish-green paint. When BGA washes up on shore, it can form a thick mat on the beach. BGA can reproduce rapidly in water bodies with adequate amounts of sunlight and nutrients such as phosphorous and nitrogen. It is recommended that individuals avoid swimming or participating in water recreational activities in areas where the water is discolored or where you see foam, scum, or mats of algae on the water.

If you see a BGA bloom, the Oklahoma Department of Environmental Quality (ODEQ) recommends you avoid all contact with the water, keep your pets and livestock away from the water and immediately contact ODEQ at (800) 522 0206 or GRDA at (918) 256 0911.

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