A cyanobacteria bloom.

Cyanobacteria blooms have been reported in Island Pond and Highland Lake in Stoddard, according to the N.H. Department of Environmental Services.

However, in a Friday news release, DES said that the blooms observed in Island Pond had begun to dissipate by the time they were reported on May 27. While the bacteria had been reported on Highland Lake, it was not observed from public beaches on Friday when samples were taken, according to a DES spokeswoman.

“We informed the town and the association about [Island] Pond but did not have any more details on Highland,” spokeswoman Amanda McQuaid said in an email Monday morning. “I think these were quick and isolated events.”

According to the news release, cyanobacteria are naturally found in bodies of water across the world, but some of these bacteria can release toxins that can have both acute and chronic impacts on human health. Acute reactions can include skin irritation, numbness, vomiting, seizures and diarrhea, while chronic effects can include liver or central nervous system damage, the release said.

People who use these bodies of water for fishing, swimming, boating or other purposes are urged to avoid these areas when blooms are observed. This applies to pets as well, according to the release.

DES has asked people to continue to monitor conditions in their local bodies of water. The bacteria may appear as green streaks or blue-green flecks along the shore, the release says.

“It is best to avoid areas where you can see it,” McQuaid said. “Anything that appears cloudy or discolored, even if you think it is just pollen, is best to avoid direct contact with.”

Both physical and chemical factors contribute to the formation of cyanobacterial blooms in fresh water, according to the federal Environmental Protection Agency, including light availability, water temperature, alteration of water flow, pH changes and nutrient loading.

McQuaid said the @NHDES — beaches Twitter page has photos of what cyanobacteria blooms look like, and that photos can be sent to 848-8094 if anyone thinks they may have seen a bloom.

Mia Summerson can be reached at 352-1234, extension 1435, or Follow her on Twitter @MiaSummerson.