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Utah Lake has reopened — with restrictions — after a toxic algal bloom poisoned the water about two weeks ago, leading to the recreation hot spot's closure.

The algal bloom, which spread to other waterways including the Jordan River and other tributaries, was dissipating, according to a news release Thursday from the Utah Department of Environmental Quality (DEQ).

Officials continued to warn patrons against swimming and other activities that require them to have contact with the lake water, but the agency downgraded the closure to a warning. People using the lake are asked to "remain watchful and report any changes in water color that may indicate presence of blue-green algae," the release said.

Rapid algal growth is more likely to occur when there are elevated nutrient levels, warm temperatures, sunlight and stagnant water conditions, the release said.

Though not all algal growth is harmful, some types contain cyanobacteria, which can cause headache, fever, diarrhea, abdominal pain, nausea, vomiting and allergiclike reactions with skin contact, according to the DEQ. If ingested, it can be fatal.

Toxin tests and monitoring at the lake are ongoing, the release states, and officials expect additional results to come early next week.

Though health officials plan to scale back on sampling next week, water bodies that persistently have shown high toxin levels or are "important for drinking water supplies" will remain a priority, the DEQ website said.

The reopening is "encouraging news," according to Ben Holcomb, coordinator of the Division of Water Quality's harmful algae bloom program, but "blooms can reappear, so we remain cautious."

Last week's sampling results show "low to no detection of toxins" in Utah Lake's open water, aside from the Lincoln Beach/Harbor area, where samples were "much greater than the recreational threshold."

All samples taken Tuesday, according to the DEQ, showed cell counts below 100,000 cells per milliliter of water, the level considered harmful to humans. Some samples remained above the level of 20,000 cells per mL, which signifies that an advisory should be issued. The highest recorded count — taken about a mile east of Pelican Point — was in excess of 73,000 cells per mL.

All but one of the "numerous" samples taken July 20 from Utah Lake and several canals in western Salt Lake County had toxin levels that were either "too low to detect" or were below a microgram per liter of water, the website said. A sample from Lincoln Beach contained 63 micrograms per liter of the cyanotoxin microcystin, three times the recommended threshold for recreational water use.

The lake originally closed July 15 at the order of the Utah Department of Health and the Utah County Health Department when algal cell concentrations were three times the threshold considered "an acute health risk" by the World Health Organization.

Cyanobacteria was present in the Jordan River and related canals on July 17, further testing confirmed, and the Utah Department of Agriculture and Food "strongly advise[d] farmers and ranchers against using water from Utah Lake for food production and livestock watering," the release said.

Canal companies temporarily shut off secondary water as a precaution, the release said; the agricultural advisory was lifted July 22.

Drinking water was not at risk.

The affected portion of the Jordan River in Utah County was not closed, the release said, but health officials installed signs along the waterway, warning people and their animals of potential harm from toxins.

Officials took samples from Salem Pond and Payson Lake on Thursday, the DEQ website said, because the bodies of water had shown signs of algal blooms.

The Utah Poison Control Center reported Thursday a low volume of calls related to the algal bloom were coming in, according to the DEQ website. As of Thursday, there had been 627 calls related to the bloom, with 511 related to human exposures, 27 related to animal exposures and 87 requesting information.

The percentage of callers who reported symptoms, ranging from gastrointestinal distress to headaches and skin irritation, was about 30 percent, the website said.

Updates on the algal bloom are available on the DEQ website.

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