ROXBURY, NJ – As area residents and businesses wait to see if Lake Hopatcong will be impacted by a harmful algal bloom (HAB) for the second consecutive summer, the state today announced a change in the way it will provide that information.

The state Department of Environmental Protection (DEP) said it will be using a new color-coded health alert index this year “to provide the public with strong and clear guidance on suitable recreational activities” when it comes to HABs.

“The new index will make it clearer to the public that, in some instances, boating and related activities may still be permissible when lower levels of harmful algal blooms are detected,” said the DEP.

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The state was criticized by many last summer for warning people to stay out of the water if cell counts of Cyanobacteria – the microorganisms in HABs – reached 20,000 cells/ml. Many said the level was too low to warrant concern.

First noticed in June - prompting the DEP to order the closure of all public beaches and warn people to stay away from the water - the 2019 Lake Hopatcong HAB produced cell counts of up to about 115,000. However, the levels of toxins (microcystins) in the water never rose to levels deemed dangerous.

The DEP pointed out that the presence of high concentrations of HAB cells can cause health issues even if there are low levels of toxins. But if the HAB cells begin pumping out toxins, contact or ingestion can result in serious illnesses, it said.

“Based on data collected over the past three years, in particular last year, DEP scientists determined that harmful algal blooms become statistically more likely to produce toxins when cell counts exceed 80,000 per milliliter,” said the state. “Consequently, the DEP has developed this cell count level as the benchmark for posting recreational alerts where all primary recreation including swimming is not recommended and local health authorities close beaches.”

The DEP said its new “tiered” alert system will be more nuanced than the one used in 2019.

“DEP scientists carefully reviewed data collected during harmful algal blooms that occurred in New Jersey over the last three years to develop a tiered warning system that will enable lake communities, residents and visitors to make more individualized decisions about what risks they are willing to take and what activities they feel comfortable engaging in at the various levels of HABs,” said DEP Commissioner Catherine McCabe.

Although McCabe said the state “can’t predict with certainty when harmful algal blooms will occur,” she said its new alert system will enable responses to HABs that will be “much more predictable and targeted, which should provide much more certainty as well as flexibility for residents and businesses to make sensible decisions.”

Shades of Danger

The new program uses a color-coded alert index the DEP said will provide “much greater precision on recreational use recommendations for impacted water bodies based on levels of cyanobacteria and/or cyanotoxins present.”

There will be five tiers of HAB advisories - Watch, Alert, Advisory, Warning and Danger

According to the DEP:

  • A Watch will be posted when cell counts exceed 20,000 “to notify the public of potential less serious health effects and allow them to make informed decisions about their recreational activities."
  • The Alert level, for public bathing beaches only, will be issued when an HAB has been confirmed with cell counts between 40,000 and 80,000 and no known toxins above the public health threshold. “At the Alert level, the index suggests that beaches increase monitoring for future toxin production,” the DEP said.
  • An Advisory will be posted when cell counts exceed 80,000 cells or when toxin levels exceed 3 micrograms per milliliter of microcystins.
  • The Warning and Danger tiers “are designed to communicate HABs that are producing very high levels of toxins which justify additional caution,” the DEP said. It noted the state “has experienced approximately a dozen HAB events over the last three years that would trigger a Warning,” but there has never been an HAB event bad enough to reach the new Danger alert level.

The state said exposure to Cyanobacteria cells can cause a range of mild to moderate health effects including rashes, allergy-like reactions, flu-like symptoms, gastroenteritis, respiratory irritation and eye irritation.

But “incidental ingestion of water containing the toxins these bacteria can produce, known as cyanotoxins, can result in more serious health effects such as liver toxicity and neurological effects," said the DEP. "Children and pets are more vulnerable because they ingest more water in relation to their size.”

See some of TAPinto Roxbury's coverage of the 2019 Lake Hopatcong HAB:

Swimming Banned at Hopatcong State Park in Roxbury and Other Public Beaches

Officials: Lake Hopatcong Harmful Algae Bloom Largest in State History

High Levels of Harmful Bacteria in Lake Hopatcong Lurk Below Clear Water, says State

High-Tech Buoys to Monitor Algal Bloom at 'Out of Balance' Lake Hopatcong, says State

Roxbury Mayor Wants More Precision in Lake Hopatcong Swim Advisories

Algae Bloom Powwow Brings Governor to Roxbury

Lake Hopatcong Mayors Don't Forget Algal Bloom as Virus Battle Continues