LAKE HOPATCONG, N.J. (CBSNewYork) — A lake warning continues in the northern part of the Garden State.

Dangerous algae is keeping swimmers out.

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But across the border in New York, lakefronts are open.

The slick green appearance of Lake Hopatcong is ruining what is usually a busy summer season for boat rental companies and others.

“Normally, the lake is packed. It was completely empty and even like weeks after that, like, there was nobody out there. They don’t want to take the risk,” resident Britney Bischoff told CBS2’s Meg Baker on Tuesday.

The owner of one market said he’s only holding on to 25 percent of his business because the folks coming in are all locals. There are no vacationers.

“Nobody on the lake, so there’s no business,” Prashant Patel said.

MORESwimming Advisory Partially Lifted At Lake Hopatcong

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A toxic algae bloom has been fueled by high temperatures and heavy rain storms. The same thing is happening up at Greenwood Lake on the New Jersey side. Yet, the New York side of the lake remains open.

Web Extra: Some NJ Lakes Still Closed Due To Toxic Algae:

Ramapo College professor Dr. Angela Cristini said a number of factors are at play. The two states have different protocols for testing and, “The wind and the currents within the lake push the bloom to the New Jersey side. The New Jersey side has shallower coves,” Cristini said.

The New York side is 40-50 feet deep. The New Jersey side is much shallower, at 10-20 deep feet.

State Sen. Joseph Pennachio questioned how the New Jersey Department of Environmental Protection sets it standards.

“I’m hoping that we have hearings, quite frankly legislative hearings, again, to find out who created this formula, how is this formula created, why our standards are different,” Pennachio said.

The NJDEP said chemical remediation methods that kill bacteria often backfire in large lakes, causing the bloom to come back even stronger. For now, it’s up to Mother Nature. The state said the last sampling did show lower toxin levels.

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Toxic algae can cause skin rashes, digestive issues, eye infections, and can be more harmful to pets.