Algal blooms force closure of beach at North Jersey's largest lake

The latest heat wave to hit North Jersey may have snapped, but the effects left from the steamy weather has led to the formation of a harmful algal bloom in Lake Hopatcong, forcing the beach area of the state's largest lake to close.

The closure of the popular Hopatcong State Park beach area in Landing comes just over a week after lake officials feared the rising temperatures and oppressive humidity could pose a threat to the nine-mile-long freshwater attraction.

A water sample tested from the beach the morning of July 16 showed concentrations of cyanobacteria, the type of algae in the blooms, at 86,875," according to an interactive map on the New Jersey Department of Environmental Protection's website. The concentrations triggered an "advisory," which goes into effect when counts pass the 80,000 threshold, during which the DEP recommends public beaches close and warns the public to avoid water contact in the area.

The Lake Hopatcong Foundation alerted the public to the findings and announced the beach's closure for swimming in a Facebook post Tuesday afternoon. The notice also indicated HABs were found in the center of Byram Cove further north, an area also placed by the DEP under "advisory."

The state park's fountain, which was turned on Tuesday morning for the first time in 30 years to a large crowd of onlookers, will remain off while the beach is closed "due to possible aerosol conveyance of cyanotoxins," the foundation said.

HABs, or algal blooms, are caused by cyanobacteria that grow out of control and, in the right conditions, can produce toxins that can kill fish, mammals and birds and can cause illnesses to humans.

Exposure to the cyanobacteria cells can cause rashes, allergy-like reactions, flu-like symptoms, gastroenteritis, respiratory and eye irritation, according to the NJDEP. Ingestion of water containing the toxins the blooms produce, called cyanotoxins, can result in headaches, sore throat, nausea and diarrhea, and more serious health effects including liver toxicity and neurological effects.

The water in Lake Hopatcong had been tested several times since May and was negative for HABs on July 10, the DEP map shows. The region's heat wave, which lingered for days before breaking on Friday, proved to be the perfect storm for the creation of the blooms, which often look like spilled paint.

Marty Kane, chair of the Lake Hopatcong Foundation, told NorthJersey.com last week recent readings of water samples in the lake reached 86 degrees. He also raised concerns about the formation of the blooms had the extreme heat not subsided, noting that he believed the lake might hit record water temperatures this summer.

Harmful algal blooms are more likely to grow in still, slow-moving water that is warm and nutrient-rich, all properties exacerbated by prolonged periods of hot, sunny weather.

Updates on the closure of the beach can be found on the NJDEP's Hopatcong State Park Page.

Email: lcomstock@njherald.com; Twitter: @LoriComstockNJH or on Facebook.