ROXBURY, NJ – The state’s advisory to steer clear of the water in Lake Hopatcong was lifted today for Henderson Cove as concentrations of potentially harmful bacteria in that area remained below the level considered risky.

The announcement by the state Department of Environmental Protection (DEP) related to results of water samples taken July 30. The DEP said it found 11,250 cells per milliliter of HAB cyanobacteria in the cove.

The state warns people to not come in contact with water that contains 20,000 cells per milliliter or more of cyanobacteria.

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Henderson Cove was found to have 17,250 cells/mL on July 25 and 40,000 on July 23.

Henderson Cove is the second place in the lake to be released by the DEP from the water contact advisory. The state on July 26 lifted the advisory for Indian Harbor. The latest samples showed that section to have 17,750 cells mL.

Good News, Bad News

Cell counts decreased in a number of other testing sites, but not in all. For example, the state said it found 59,500 cells mL in Woodport Bay on July 30, a place that had only 19,750 cells mL in the prior test but had 78,000 in the one before that.

Swimming at Hopatcong State Park remains banned. The July 30 sample found 35,000 cells mL, about half the concentration recorded July 25. Byram Cove, which had 50,050 cells mL on July 25 showed improvement, registering 25,500 cells mL on July 30.

"New Jersey’s protocol for issuing harmful algal bloom advisories and beach closures are based on its 2017 Harmful Algal Bloom Response Guidelines," the state said today. "These guidelines incorporate scientific and public health recommendations published by the World Health Organization and others ...That guideline is set at 20,000 cyanobacteria cells per milliliter of a water sample. When this level of bacteria is exceeded, the science shows that we can expect 3 in 10 people who have contact with the water to develop skin rashes or other allergy-like responses, or to experience gastro-intestinal distress."

Although the cyanobacteria can cause skin rashes and gastrointestinal issues, none of the HAB plumes on the lake have been found to be producing dangerous levels of poison known as microcystins. These toxins can cause more severe illnesses, according to the DEP.

Remember Lake Okeechobee

This topic was addressed in a TAPinto Roxbury guest column by Monmouth University Biology Department and Urban Coast Institute professor Jason Adolph, who runs the Phytoplankton and Harmful Algal Bloom research lab at the university.

“The latest measurements … show that HABs are occurring without high toxin levels,” wrote Adolph. “However, this can change and it is worth noting that the public health crisis presented by a lake full of toxin-producing HABs is far greater than what we are currently seeing, as evidenced by the highly toxic HABs that occurred in Florida’s Lake Okeechobee in the summer of 2018.”

The state issues health advisories when HAB toxin levels reach 3 parts per billion (ppb). No sites in Lake Hopatcong have come close to that level, but the same can’t be said for Greenwood Lake, which is also suffering from an HAB outbreak. Microcystins levels of 4.84 ppb were found recently in one sample site at that lake, according to the DEP.

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