Phosphorus threatens a key bay in Lake Champlain. WAMC’s North Country Bureau Chief Pat Bradley reports on the Lake Champlain Basin program and other stakeholder’s efforts to stem the pollution.
Missisquoi Bay is a 30-square-mile shallow arm in the northern part Lake Champlain. It stretches across the border into Canada, and in 2002 the U.S. and Canada agreed to share responsibility to reduce pollution entering the bay. The agreement was renewed in 2021 with a focus on targeting phosphorus pollution.
To that end, stakeholders, including representatives from the Vermont Agency of Natural Resources, held a hybrid meeting in Quebec Tuesday to discuss ongoing mitigation efforts. Lake Champlain Basin Program Chief Scientist Matthew Vaughan presented copious data on phosphorus loading from rivers and noted the chemical is the key driver of water quality in the bay.
“We have too much phosphorus. That's why we need to limit it and reduce the amount of phosphorus going to Missisquoi Bay to ultimately reduce what's in the bay and to reduce the problems we have with cyanobacteria blooms, for example,” Vaughan explained.
Vaughan traced the entry of phosphorus into the lake and bay through rivers and efforts to reduce runoff from those streams. He went on to discuss legacy phosphorus, a key challenge that caught the attention of stakeholders.
“Legacy phosphorus is phosphorus that's been deposited through today and it remains there at the lake bottom. That can release phosphorus from the sediments into the water column. So that is a major contributor to our water quality problem, not just phosphorus coming from the rivers or from the watershed, but also phosphorus that's been deposited decades in the past. So it's a very important piece of the puzzle. There's a lot of phosphorus there that is contributing to our water quality challenges,” Vaughan said.
Vaughan was asked if there are potential controls of legacy phosphorus that would prevent its release into the water column.
“A study was funded recently to look at different options for Missisquoi Bay. These include things like aerating the water so that it does not provide conditions that can release phosphorus. You can dredge and physically remove the phosphorus and then you can add chemicals to the water and not let it be released. For Missisquoi Bay the study concluded that the only really path forward was Alum treatment. It would be unusual to use Alum on water body this size, but it is the option to consider,” Noted Vaughan.
Quebec stakeholders also provided reports, mostly in French, on the province’s efforts to reduce phosphorus and improve water quality in Missisquoi Bay.
