Geneva lakefront HABs

Blue-green algae toxic blooms found in north end of Seneca Lake

GENEVA — The fifth week of sampling for harmful algal blooms in Seneca Lake has resulted in a major spike, consistent with last year’s time line.

Seneca Lake Pure Waters Association volunteers took 46 samples from the shoreline Sept. 2-8. Thirty-seven of those — and possibly more when testing is completed — were found to exceed the 25 micrograms-per-liter criteria to be toxic.

“For the last four weeks our volunteers and Seneca Lake residents have been wondering if the lake would ever be hit with a major outbreak of HABs like many other Finger Lakes,” said Frank D’Orio, the HABs director for Pure Waters. “No one needs to wonder any longer.”

The 120 Pure Waters volunteers collected 20 samples on Sept. 5, 17 on Sept. 6, and eight on Sept. 8. D’Orio said the samples came from all areas of the lake.

The Finger Lakes Institute in Geneva conducted the initial testing. The Upstate Freshwaters Institute in Syracuse will look for additional toxins in many of those samples.

As of Monday night, 37 samples were confirmed as blooms, while two were below the criteria.

“This year’s pattern is roughly consistent with last year,” D’Orio explained. “In 2018, the first big bloom day was Sept. 4. Then blooms periodically sprang up from Sept. 9-27, with the most intense blooms coming in Sept. 11-13. Expect more blooms and the bloom season to peak in the next two weeks and then taper off the last week of September.”

D’Orio suggested people treat all blooms as toxic.

“Chances are the bloom you see is toxic,” he noted.

Pure Waters volunteers will continue sampling until Oct. 6.

For up-to-date information on Seneca Lake HABs, go to and to view the map and associated instructions.

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