Kershaw Beach was closed Thursday for precautions after blue-green algae was confirmed on Canandaigua Lake

Just as people are looking forward to the Labor Day weekend, Canandaigua Lake has joined the ranks of waterways statewide with blue-green algae.

In the Finger Lakes, Seneca Lake last month had its first confirmed blue-green algae bloom and Honeoye Lake has visible patches of the noxious substance. Now, samples tested this week on Canandaigua Lake have confirmed the presence of blue-green algae.

Samples from Canandaigua Lake are undergoing further analysis to determine whether the algae is producing a toxin that can be harmful to humans and other animals, according to the blue-green algae advisory posted by the Canandaigua Lake Watershed Council. Those results are expected to be available Friday.

Meanwhile, public health officials on Thursday warned people to be careful.

“Do not boat or swim and do not let dogs swim into blooms,” advised Ontario County Public Health Director Mary Beer. “You do not want to get exposed. If you get exposed, wash it off right away."

John Goodwin, assistant Canandaigua city manager, sent out a release Thursday afternoon, informing the public that the city’s Kershaw Beach was closed until further notice.

“The Ontario County Health Department has announced that blue green algae exists in the northern and middle sections of Canandaigua Lake. Though no blooms have been found in the vicinity of Kershaw Beach, in an abundance of caution we are closing the beach effective immediately until we receive updated information through the Department of Health that the waters are safe,” he stated.

Good news could come as early as Friday, he stated. “We apologize for any inconvenience.”

Canandaigua Lake Watershed Manager Kevin Olvany said Thursday that some test results from samples taken Thursday from the east side of the lake were “more in line with lower risk levels.” Olvany said that is a positive sign in monitoring the ongoing condition of the lake.

Olvany and Bruce Gilman, professor of environmental conservation at Finger Lakes Community College, along with citizen volunteers, have been sampling and monitoring the lake. According to the Watershed Council, they found a reduction in water clarity on Friday, Aug. 28 through Tuesday, Sept. 1, along with an associated increase in algae that included algae producing streaks along the surface. Two water samples were sent to the lab for analysis at the State College of Environmental Science and Forestry in Syracuse to identify and quantify algae concentrations. Lab results received Wednesday evening identified the dominant algae as a blue-green algae, specifically microcystis.

Olvany said Thursday, as he was monitoring further algae evidence around the lake, that microcystis occurs naturally and becomes a concern when found in higher concentrations.

One of the two samples that came back confirmed for blue-green algae was from the middle of the lake, about 1,000 feet south of the buoy markers for the boats to go 5 mph, or about a half mile from Kershaw Beach.

“The second sample was also collected in the middle of the lake just north of the Yacht Club in another surface streak of algae and the results were more concerning,” according to the notice. These samples are undergoing additional analysis to determine whether the algae is producing a harmful toxin.

“It is important to point out that concentrations of algae can vary significantly across the lake based on wind conditions and other variables. The samples were purposely collected in the areas that had higher concentrations to get a sense of plausible worst case scenario conditions where people would be in contact with the water,” according to the notice.

Visual observations by the watershed manager and inspector along both sides of the lakeshore showed that the southern half of the lakeshore was much clearer than the northern half of the lake.

 “The northeastern half of the lake seems to have the highest concentrations based on the prevailing southwesterly wind patterns," the notice reads. "However, this can change rapidly. Additional samples were collected Wednesday along the east side of the lake based on higher concentrations visually observed.”

Watershed groups are working closely with the state Department of Health and Department of Environmental Conservation to document the algae levels and determine if the algae is considered to be harmful to humans and animals.

“Many lakes are dealing with this issue and they have concentrations much higher than our lake,” the notice stated. “However, the surface streaking and the high blue green concentrations are not a common occurrence on this lake and needs to be taken seriously. At the same time, there are large sections of Canandaigua Lake that are in good shape. It is recommended that you use caution and common sense when entering the water. Be on the lookout for larger concentrations of algae and avoid contact with water that has streaks of algae ... water that has a surface scum, looks like pea soup or green paint.”

People are asked to report observations regarding algae to Olvany at (585) 747-8719 or

Questions? Symptoms?

Ontario County Public Health: (585) 396-4343;

About blue-green algae advisory: Canandaigua Lake Watershed Association —

About blue-green algae notices: New York State Department of Environmental Conservation —