Wetter, cooler summer meant lower levels of blue-green algae in Allegheny Reservoir

A cooler, wetter summer may be part of the reason for lower concentrations of blue-green algae blooms in the Allegheny Reservoir in New York and just south of the line into Pennsylvania.

That’s the assessment of Eric Wohlers, director of the Cattaraugus County Health Department’s Environmental Health Division, after reviewing data on the most recent round of samplings by the U.S. Army Corps of Engineers.

Three areas of the reservoir — Quaker Bay shoreline, Sawmill Bay shoreline, and Willow Bay — continue to operate under a World Health Organization (WHO) advisory due to levels of blue-green algae exceeding 20,000 parts per milliliter (ml).

Quaker Bay, which showed a high of 457,336 parts per ml in samples from Aug. 18, dropped to 59,438 parts per ml in samples collected Aug. 25. This is still above the 20,000 parts per ml that requires warning for boaters and swimmers, and warning signs remain up at all three sites.

“The numbers are still low compared to the last couple of years at this time,” Mr. Wohlers said. The warning signs will remain up as long as the tests show samples above 20,000.

“This summer has been cooler and we’ve had quite a bit of rain,” Mr. Wohlers said.

The Health Department hasn’t received any reports of people or animals getting sick from contact with blue-green algae.

It can look like the color of pea soup, and be slightly luminous.

“The Army Corps of Engineers is doing a fantastic job of posting signs at access points and boat launching sites,” Mr. Wohlers said.

The blue-green algae blooms have occurred in the upper part of the Allegheny Reservoir and bays, he said. This is where the heavy load of nutrients from the Allegheny River and its tributaries enters the reservoir. Further south, the Allegheny National Forest offers fewer nutrients because of the lack of agricultural land.

“The Corps expects to sample in September and into October until the bloom ends, or drops below cautionary or advisory levels” Mr. Wohlers said.

The 475,366 parts per ml level near the Friends Boat Launch  in Quaker Bay on Aug. 18 was the highest blue-green algae bloom reported on the reservoir this summer. The WHO caution level is 100,000 parts per ml. On July 28, the level was 158,752, and on Aug. 4 it rose to 247,661 before dropping to 40,820 on Aug. 11.

The bloom in Sawmill Bay, where the Onoville Marina Park is located, showed a cautionary 255,437 level on Aug. 4, after recording a 34,013 level the week before. It dropped to 37,626 on Aug. 11, and dropped below the advisory level to 12,256 on Aug. 14, before rising to 25,681 on Aug. 18, and 43,446 on Aug. 25.

Pennsylvania’s Willow Bay results hit a high of 28,760 parts per ml on Aug. 25, and another advisory level of 25,213 parts per ml on Aug. 11. Four other samples from Willow Bay were all below the 20,000 parts per ml level.

Advisory level signs will remain in place at Sawmill and Willow bays, and the caution level sign at Quaker Bay — until blue-green algae counts remain below action levels for at least two weeks.

A blue-green algae bloom was reported at Lime Lake in Machias in June, but was found to have ended by the time the lake water was sampled on July 1.


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