Lake George algal bloom: harmful but not too toxic

By Ry Rivard

The harmful bacteria that bloomed a week ago in parts Lake George was not a major danger to drinking water supplies, according lab work by the state.

Last week, Lake George had an outbreak of cyanobacteria, commonly referred to as a harmful algal bloom. While cyanobacteria had appeared beneath the surface in recent years, this outbreak was the first confirmed bloom to foul the surface of the lake, which is renowned for clarity that attracts homeowners and tourists from around the country.

The bacteria are not simply unsightly but can also produce toxins that attack the kidneys, liver or nervous system.

Recent tests did not find such toxins in the lake.

“We thank DEC for their assistance in getting this test performed and for providing these results, and for helping us to keep the lake community informed,” said Walt Lender, the head of the Lake George Association.

According to the terminology around cyanobacteria and algae, a bloom can be labeled harmful without being toxic. Likewise, there can be toxins in the water that are not discovered or labeled as a harmful bloom. While a bloom is happening, people are advised to avoid swimming in or drinking from the water. Boiling cyanobacteria-filled water doesn’t remove the toxins. 

The bloom spread out around Assembly Point and moved through several bays on the south end of the lake near the Village of Lake George, then dissipated within several days. Thousands of people get their water from the lake, though typically they filter it somehow before drinking.

Lake watchdogs have warned for years that rising pollution levels in the lake — fueled in part by leaking lakeside septics — would help cause such a bloom.

In 2018, Gov. Andrew Cuomo released a series of plans to protect lakes across the state from toxic blooms. Lake George’s plan called for mandatory septic tank inspections by 2021. There’s no sign of that happening, though.

Correction: Recent water quality measurements by the state did not find toxins in Lake George. A previous version of this story said toxins were found at a low level.