What is the concern with cyanobacteria
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.

algae bloom on Lake Champlain beach

Photo: Mary Watzin

blue-green algae alerts graphic

Figure 9 | Blue-green algae alerts, 2012-2014

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.

What causes cyanobacteria blooms graphic

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.

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Not just a Lake Champlain Problem!

Lake Erie blue-green algae bloom

Other regions also face significant challenges from cyanobacteria. This October 2011 satellite image of Lake Erie with the outline of Lake Champlain superimposed illustrates the relative size of these challenges.

Cyanobacteria (blue-green algae or BGA) blooms are not unique to Lake Champlain. According to the US EPA, the Northeast has among the lowest number of reported BGA blooms in the country (Carmichael 2006). The Interagency Working Group on Harmful Algal Blooms, Hypoxia, and Human Health states that BGA blooms have been documented in at least 35 states, and at least 18 states now have BGA research or response programs (Lopez et al. 2008). According to the US National Office of Harmful Algal Blooms, harmful inland and freshwater BGA blooms are most widespread in the Great Lakes Region. BGA blooms have been increasing in Lake Erie since the 1990s—in 1995 a bloom covered the western third of Lake Erie (US EPA Large Lakes and Rivers Forecasting Research Branch 2011).

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