2016: Don’t go in the water when the paint-like algae are present.
Steve Orr/Angie Nassar
A very small bloom of potentially toxic blue-green algae was discovered last week in Hemlock Lake, the primary source of Rochester drinking water, but city officials say water quality was not affected.
The bloom was found Wednesday by a city employee who works at Hemlock, one of two largely undeveloped Finger Lakes and the source of city drinking water for the last 141 years.
The bloom, toward the northern end of the lake but still several thousand feet from the spot where the city draws lake water into its treatment plant, reportedly dissipated the following day.
There was no public announcement of the occurrence, and city and state officials described it as insignificant.
“I can only stress that due to its location and limited size and duration, the bloom didn’t appear to have any impact whatsoever on water plant operations or on water quality,” said city spokesman James Smith.
Water-system operators throughout upstate New York have been on alert for algal blooms this summer, however, because of woeful experience last year at Owasco Lake in Cayuga County.
Significant algal blooms released toxin in the water of that Finger Lake, and some of the toxin later was found in treated drinking water being piped to customers of two municipal systems.
It was the first time such a thing had ever happened in New York, though concentrations were low enough that no one was sickened.
Two samples were gathered at Hemlock to test for algal toxin but results are not available yet, the state Department of Environment Conservation said Tuesday.
Under the right circumstances, blue-green algae — actually, the organism is an algae-like form of photosynthetic bacteria — can proliferate quickly, or bloom. Certain forms of cyanobacteria can release toxins that attack the liver or nervous system, causing symptoms both minor and serious.
Some had predicted that this summer would be a bad one for blue-green algae blooms in New York state. Midway through July, the DEC had noted algal blooms on 55 different lakes, ponds and reservoirs this year.
At about the same time last year, 48 water bodies had made .
The latest DEC list included small localized blooms at Conesus Lake in Livingston County and Honeoye Lake in Ontario County. The bloom at Honeoye forced the closure of Sandy Bottom Beach there, officials said.
Small, semi-private Lake Lacoma in Perinton was added to the list for a second time this summer, triggering the first-ever public notice from the Monroe County Department of Public Health.
After being criticized last year for failing to warn the public of several local algal blooms, the county said recently it would begin using Twitter to alert people.
The Monroe County health department, which has oversight of Hemlock Lake because it supplies drinking water to tens of thousands of Monroe residents, made no public notice of the small bloom there.
The event also was omitted from the weekly update of harmful algal blooms released by the DEC on Friday. The agency did include the Hemlock bloom on a more obscure archive page, where the Democrat and Chronicle noticed it Tuesday.
The state agency said it didn’t note the Hemlock bloom on the more conspicuous list because city officials told the DEC the bloom had dissipated before the list was put together last Friday.
Smith said Hemlock Lake, like nearly every other lake and pond, is home to various kinds of blue-green algae. But algal blooms there and in neighboring Canadice Lake, which also supplies drinking water to the city, are quite rare and low impact.
“Typically the blue-green algae blooms in Hemlock have not presented a challenge in terms of water quality,” he said.
This bloom, which Smith described as no more than 100 square feet in size, involved a type of cyanobacteria, Dolichospermum, that can release a potent neurotoxin.
Smith said city employees have stepped up their inspections of the lake shore to watch for further blooms and are in ongoing contact with DEC officials about the situation.
A man kayaking records a black bear swimming next to him in Hemlock Lake.
Video provided by Matthew Garrity.
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