One large New Jersey lake reopened Wednesday but another remained closed because of a potentially poisonous bacteria.

Lake Hopatcong at Hopatcong State Park reopened to swimming and recreational activity on Wednesday after water passed all quality tests, according to a notice on the park's Facebook page. The was closed on Monday due to high levels of bacteria.

Deal Lake in Monmouth County, meanwhile, remained off limits because of high levels of algae bloom that can produce toxins that are poisonous to humans and animals that ingest, breathe in or come into contact with the blue-green scum. The advisory was first issued by the the Monmouth County Health Department on July 26.

The county will re-test the water on Thursday and lift the advisory once bacteria levels are lower and the water is considered safe.

According to the NJ Department of Environmental Protection, algal bloom is a rapid increase or accumulation in the population of algae and algae-like bacteria in a body of water. The "blooms" often result in a thick coating on the surface of the water, which can also result in lowering the dissolved oxygen in the water column.

The blooms do not always produce toxins but if they do, rashes can occur when cells come in contact with the skin and ingestion can result in gastrointestinal issues.

Deal Lake is a 158-acre man-made lake that stretches through seven towns. It is mainly used for recreational activity such as boating and fishing and contains both fresh and salt water.