Authorities have detected elevated levels of a dangerous algal bloom in a New Hampshire lake, prompting them to warn people not to go near it. Samples collected from Lake Monomonac on July 17 have exceeded the threshold of 70,000 cells per milliliter or greater of blue-green algae, also called cyanobacteria.

The heaviest of the blooms were found near the shore, and the cyanobacteria was identified as Aphanocapsa, Woronichinia, and Anabaena. While such bacteria is a natural occurence in bodies of water around the world, a sudden bloom happens when excessphosphorus is found in the water, and it can result in health hazards for humans.

The negative effects from exposure to cyanobacteria include skin irritation and liver damage.

“An elevated cyanobacteria cell concentration has been measured in Long Pond, Pelham, NH,” according to a statement from the statement from the New Hampshire Department of Health and Human Services. “Samples collected at the Pelham Town Beach on July 17, 2017 revealed that the state threshold of 70,000 cells/ml or greater of cyanobacteria was exceeded. The cyanobacteria were identified as Anabaena, Microcystis and Woronichinia. As a result, the New Hampshire Department of Environmental Services (NHDES) has issued a cyanobacteria warning for those who recreate on Long Pond. The current bloom is variable with some lake portions free of scum sightings, while other areas have accumulations of cyanobacteria along the shorelines or beaches.”