Guest column

Blue-green algae found in Lake Iroquois

Oct, 27, 2011

By W.C. Wright


September brought a bloom of blue-green algae (aka cyanobacteria) back to Lake Iroquois for the second consecutive year. These blooms are caused by excessive nutrients entering the lake from stream erosion, shoreline erosion, poor management procedures during construction of buildings and roads, road erosion, wastewater disposal systems (septic systems) and stormwater runoff.

The “pea soup” appearance of the water and the blue-green-yellow sheen (looking like spilled paint) on the water surface are characteristic of cyanobacteria blooms. The toxin that is sometimes produced by this algae is known to have caused illness and death of dogs that drank the water.

Upon seeing the new bloom, we notified the Water Quality Division of the Vermont Department of Environmental Conservation and health officials in the towns of Hinesburg and Williston.

Rocky Martin of the Hinesburg health office responded by contacting the Vermont State Health Department and — with the help of Lake Iroquois Association Board member Dan Sharpe — collected samples from the southwest corner of the lake, where the bloom was most apparent. Signs were also placed at the fishing access and beach area warning people to avoid the algae and to keep their dogs out of the bloom.

Sample water tests confirmed the presence of blue-green algae toxins, but thankfully in lower concentrations than those known to cause disease in humans or animals.  Because tests were done at a single location and time, it is likely that toxin levels could have been higher or lower if tested earlier or in a different location.

This bloom of toxin-producing algae is a concern to all of us who use and enjoy Lake Iroquois. We have read reports of blooms in Lake Champlain, especially in Missisquoi Bay, that limit swimming and the use of the water for cooking and other domestic purposes.

The Lake Iroquois Association is committed to attacking these problems. Studies have been done to identify some of the major sources of nutrient loading, and plans are underway to remedy some of them.

It is essential that all who enjoy the lake become involved to protect and improve it. Boaters, fishermen, beach users, those who have properties in the watershed, and the towns of Hinesburg, Williston, Richmond and St. George all need to contribute their efforts, time and money to make this lake a viable, enjoyable and safe place for us all in the future.

Hopefully, together we can make Lake Iroquois a model for others of how interested, dedicated individuals, organizations and towns can improve the quality of a lake — now and for future generations.

For more information on this and other lake issues go to the Lake Iroquois Association web site:

W.C. Wright is a board member of the Lake Iroquois Association.