ROXBURY, NJ – Several Lake Hopatcong beaches that have been closed to swimming since late June due to an ongoing harmful algal bloom (HAB) might re-open early next week, according to the state.

But Hopatcong State Park in Roxbury doesn’t appear to be one of them.

The state Department of Environmental Protection (DEP) said it sampled several bathing beach sites on Aug. 8 and found that concentrations of the bacteria involved in the HAB were below the level that prompts the state to issue no-swimming advisories.

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Of the nine beaches were water samples were taken, six were found to have bacteria levels below the DEP’s 20,000 cells per milliliter “health advisory guidance threshold,” said the state. It said it planned to sample the water at the beaches again on Monday.

It Takes Two

“As per the DEP/DOH (state Department of Health) Harmful Algal Bloom (HAB) Freshwater Recreational Response Strategy, two subsequent samples below the health advisory guidance thresholds are required for reopening of a regulated Public Recreational Bathing facility,” the DEP said.

The Aug. 8 tests found below-threshold levels of HAB at Pebble Beach, Sand Harbor, Bass Rock Beach, Sparry Springs Beach, Beck Lane Beach and CAPP Beach, said the state. It said it found HAB levels slightly above the threshold at Clearwater Beach, Hopatcong State Park and Byram Bay Community Beach.

Additionally, the DEP’s Aug. 8 tests showed that bacteria levels declined in other sampling sites when compared to tests taken Aug. 6.

  • Wood Port Bay had 40,000 cells/mL, a decline of 14,750 cells/mL
  • Crescent Cove River Styx had 50,625 cells/mL, a decline of 30,125 cells/mL
  • Mid-Lake East of Davis Cove had 22,500 cells/mL, a decline of 15,750 cells/mL
  • Water southeast of Hopatcong State Park Beach had 24,250 cells/mL, a decline of 17,250 cells/mL
  • Prospect Point had 28,000 cells/mL, a decline of 2,000 cells/mL
  • The middle of the lake had 37,750 cells/mL, a decline of 18,375 cells/mL

Upward Creep

On the other hand, the cell counts for Henderson Cover, Byram Cove and Indian Harbor – although still below the advisory threshold, increased between Aug. 6 and Aug. 8.

All three sites had slightly more than 17,000 cells/mL, said the DEP. The state recently lifted its water contact advisory for those three sites when HAB levels remained below the 20,000 cells/mL level in two consecutive tests.

No sites on the lake have produced water tests indicating the bacteria are generating unhealthy levels of dangerous cyanotoxins called microcystins, according to the DEP.

The state continues to use aerial surveillance of the lake to get a sense of the ebb and flow of the HAB. It does this with a sensor that “is used to pick up wavelengths of light specific to the cyanobacteria pigment phycocyanin” in the water.

The Aug. 9 aerial survey showed that “phycocyanin levels seem to have remained at the same intensity but the spatial coverage seems to be diminishing,” said the DEP. “The bloom is still present in pockets with higher levels in the south.”

The state said its advisory – warning people to not come in contact with lake water, or let their pets do so – remains in effect for all areas other than Henderson Cover, Indian Harbor and Byram Cove.

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