PROVO — An algal bloom prompted public health officials to post warnings Thursday at Provo Bay, though it was not formally closed.
Algae levels in the bay's open waters were many times greater than the threshold required for an advisory to be issued, said Donna Spangler, spokeswoman for the Utah Department of Environmental Quality.
Algae concentration in the mouth of the bay was significantly less, but still about twice the threshold for an advisory, Spangler said.
The bloom in Provo Bay was first detected "via satellite imagery," she added. Crews have monitored algae levels there since June 12.
Other parts of Utah Lake are not currently considered to be in an algal bloom. Visitors to Provo Bay will see warning signs about the risk of all recreation there, especially swimming and other activities involving getting directly in the water, said Utah County Health Department spokeswoman Aislynn Tolman-Hill.
"We know there's a lot of folks who will be interested in being out on the lake" over the weekend, Tolman-Hill said. "(The bay) is not closed, but it's something we want folks to be aware of ahead of time."
Lake visitors are also being warned against the algae's possible harmful effects on their pets, according to Spangler. Samples from the bay will continue to be collected, she said.
Spangler said unhealthy levels of cyanobacteria — commonly known as blue-green algae — arise from "high levels of nutrients in the water, combined with warm temperatures, abundant sunlight and calm water."
About 90 percent of Utah Lake was covered in an algal bloom last July, causing the lake to be closed to all recreation for nearly two weeks. At the time, Utah Division of Water Quality Director Walt Baker said 80 percent of one of the responsible nutrients, phosphorous, could be sourced to wastewater discharge from sewage treatment plants.
Also at that time, Baker cited Utah Lake's unusually low level as a likely contributing factor to the widespread bloom.
The current algal bloom could still expand or drift, Tolman-Hill said, "based on weather patterns."
"We could see additional restrictions in the future," she said.
Exposure to high concentrations of blue-green algae can lead to stomach pain, allergic-like reactions on the skin, diarrhea, fever, headache, nausea or vomiting.
Anyone who believes they may have had harmful exposure to the algae is asked to call the Utah Poison Control Center, at 1-800-222-1222, or their doctor.