What is the concern with cyanobacteria
blooms in Lake Champlain?
Harmful algae blooms occasionally occur in Lake Champlain during warm, calm summer weather. The cyanobacteria that cause these blooms sometimes release toxins into the water that are harmful to humans and other animals. Some sections of the Lake are more susceptible to these blooms than others.
Harmful algae blooms first attracted attention in Lake Champlain in 1999, when two dogs died after exposure to the toxins created under bloom conditions. In response to that event, LCBP funded and has maintained a monitoring program to detect and report harmful algae bloom conditions in the Lake. The monitoring program, which identifies three levels of algae conditions, has served as a model for other water bodies in the US and globally. By 2014, the program had transitioned largely toward a reporting program, a lakewide system of trained volunteers operated by the Lake Champlain Committee. Testing is done by the Vermont Department of Environmental Conservation, and risk assessment by the Vermont Department of Health. Certified harmful algae bloom observations from around the Lake are posted on an interactive webpage maintained by the VT Department of Health. The current program is designed to inform the public with reliable and timely information.
Harmful algae blooms most frequently occur in Lake Champlain from mid-July through August. They are typically found in the shallower, warmer bays of Lake Champlain, including Missisquoi and St. Albans bays, although they occasionally are observed in other Lake areas (Figure 9). The cyanobacteria monitoring program on Lake Champlain identifies lake conditions as one of three categories: Generally Safe, where normal levels of blue-green algae may be present, but not in bloom conditions that might create toxins; Low Alert (Alert Level 1), where algae have been observed at moderate densities; or High Alert (Alert Level 2), where algae scums have been observed in the water or toxins are present at high levels.