VERNAL — Dangerous toxins at nearly 11 times the recreation health standard forced the closure of the Matt Warner Reservoir near Vernal on Tuesday.
The Tri-County Health Department issued a danger advisory Tuesday after receiving lab data for water samples collected Aug. 6 at the boat ramp.
The agency is posting closure signs at the water body.
The onset of a blue-green algal bloom, also called cyanobacteria, indicates stagnant water and hot temperatures. Samples collected at this waterbody contained microcystin concentrations and anatoxin-a.
Microcystin is one of the most widespread in the cyanobacteria family and is a potent liver toxin and possible carcinogen.
Testing at boat ramps showed cell counts of more than 109 million per milliliter at the surface and at 1.8 million at elbow depth.
Anatoxin a is a fast-acting neurotoxin that is lethal.