Binational Partnership Studies Pollution in Missisquoi Bay

Posted on Thursday, October 1st, 2020 | Posted in News

NEIWPCC and the LCBP partner with Québec organization to address phosphorus  impacts

The increasing persistence of algal blooms in the Missisquoi Bay led to NEIWPCC’s involvement in a binational water quality report on the Lake Champlain Basin, which was finalized in April.

picture of harmful algal bloom in Missisquoi Bay

A harmful algal bloom in Missisquoi Bay. Credit Pierre Leduc.

Missisquoi Bay, the northern-most sub-basin of the Lake Champlain basin, is shared between the Province of Québec (42%) and the State of Vermont (58%).

The bay has been chronically afflicted by excessive phosphorus loads and has one of the highest in-lake phosphorus concentrations of any segment of Lake Champlain, according to the Lake Champlain Basin Program (LCBP).

By request from the International Joint Commission (IJC), NEIWPCC and the LCBP partnered with the Québec watershed group Organisme de basin versant de la baie Missisquoi (OBVBM) to conduct a comprehensive review of the bay’s nutrient problems.

Those recommendations from this collaborative effort were incorporated into a final report the IJC provided to the United States and Canadian governments, “Nutrient Loading and Impacts in Lakes Champlain and Memphramagog,” to inform the countries’ management of these binational waters that provides an overview of scientific knowledge related to regional nutrient loading and recommendations for restoring the bay..

The Phosphorus Problem

The largest source of phosphorus loading to the Missisquoi Bay is from agricultural activities, which has resulted in the accumulation of phosphorus-rich sediments in the bay over many decades.

“That large external phosphorus input, plus the fact that this is a small, shallow bay with a narrow connection to the rest of Lake Champlain, means that there is a lot of phosphorus staying in the bay and causing problems,” says Dr. Christina Stringer, NEIWPCC program manager.

With climate change, the problem is exacerbated. “The temperature of the lake is getting warmer, and warmer deeper, which causes phosphorus in the sediments at the bottom of the lake to re-suspend,” Stringer says.

“So even if we had no external phosphorus inputs, we would still have this internal loading from historical sediments.”

Restoring water quality in the bay will be no easy feat. The EPA estimates that a 64.3% reduction in phosphorus pollution is needed to meet the 2016 Total Maximum Daily Load allocation for the Missisquoi Bay segment of the Lake Champlain basin.


NEIWPCC, the LCBP, and the OBVBM worked together to assess the phosphorus problem in Missisquoi Bay with guidance from a group of experts serving on the IJC’s Champlain Study Advisory Group that was established for this study. They conducted a comprehensive literature review and interviewed state employees, subject matter experts, and other stakeholders who have a longstanding history working in the basin on these issues.

The advisory group recommended that the United States and Canada:

  • establish a permanent binational Missisquoi Bay Phosphorus Reduction Task Force as a standing subcommittee of the Lake Champlain Steering Committee;
  • develop a binational mass balance for phosphorus imports and exports in the Missisquoi Bay watershed;
  • reduce the use of phosphorus on the lands of the Missisquoi Bay watershed;
  • increase the proportion of crop systems that contribute less phosphorus to the system;
  • increase the protection and enhancement of river corridors and buffers, floodplains, wetlands, and forest lands and ensure their reconnection for nutrient storage; and
  • engage with public stakeholders to commit to clean water and healthy ecosystem goals.

“While it is difficult to predict how long the recovery [of the bay] will take, especially with the uncertainties posed by climate change and extreme events, the Champlain Study Advisory Group believes that the actions recommended in this report will accelerate the pace of recovery and increase the likelihood of successful restoration,” the report states.

The IJC incorporated these recommendations into their full report on “Nutrient Loading and Impacts in Lakes Champlain and Memphremagog,” which was provided to the United States and Canada in April 2020.