Two areas of Lake Hopatcong are demonstrating an accumulation of cyanobacteria in the DEP’s “blue range,” the Lake Forest Yacht Club and Mount Arlington beach.

The state Department of Environmental Protection instituted a new sliding scale to keep lake residents apprised of the presence of cyanobacteria in the lake this summer. This was in response to Harmful Algal Blooms (HABs) resulting in controversial beach closings during the 2019 season.

The blue range is the “watch” status, just above the green, which means no cyanobacteria present, according to the DEP chart. In that range, there may be visual evidence and water testing reveals between 20,000 and 40,000 parts per million of the bacteria.

Fred Lubnow, environmental consultant to the Lake Hopatcong Commission, said on Tuesday, July 28, that no known toxins were found among the bacteria, so public bathing beaches can remain open.

He advised dogs not be allowed in the water because they are very sensitive to bacteria and will drink the water or lick it off their fur.

“Regardless of the alert level, don’t let your dog in the water,” he said, noting any time the water looks green dogs should be kept on the shore.

The count at Lake Forest was 26,375 and at Mount Arlington at 26,000.

Six other areas were tested, including Crescent Cove, where a new aeration system was turned on Friday, July 24 just after samples were taken. The aeration system is designed to increase the movement of water, making it less likely cyanobacteria will accumulate in near shore and shallow areas, Lubnow said.

Three other areas will be aerated, two of which will be equipped with nano-bubblers, which use tiny bubbles to break up the algal cells. One of these will use just a nano-bubbler and one will inject ozone, which is designed to work against the cyanotoxins. The two affected beaches will have bubblers, Lubnow said, a decision made in January. The third area will be a beach in Roxbury.

Nano-bubblers are a new technology, he noted.

The bubblers are funded through the HABS grant from the state.

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