The EPA’s largest research vessel, Lake Guardian, on Aug. 3 launched its annual summer water quality and food-web survey of all five Great Lakes, the primary source of long-term monitoring data for an ecosystem that supplies drinking water to more than 30 million Americans.
The month-long survey will cover Lake Superior, Michigan, Huron, Erie and Ontario, collecting data on water chemistry, plankton populations, fish populations and contaminant levels.
The Great Lakes contain 21% of the world’s surface fresh water and support a regional economy worth hundreds of billions of dollars annually, including commercial fishing, shipping, tourism and manufacturing.
The Lake Guardian survey has been conducted annually for decades, providing the scientific baseline that tracks whether the lakes are improving or degrading over time. Results feed into EPA’s Great Lakes monitoring reports and binational management plans with Canada.
Specific threats the survey monitors include invasive species, nutrient pollution that causes harmful algal blooms and emerging contaminants such as PFAS chemicals. Lake Erie has experienced particularly severe algal blooms in recent years, threatening drinking water supplies for cities including Toledo, Ohio.
The Great Lakes National Program Office, based in Chicago, manages the EPA’s monitoring and restoration efforts for the five-lake system. The survey data supports federal, state and tribal management decisions and is shared with Canada through the International Joint Commission.
The survey also tracks the food web from microscopic plankton to fish populations, providing an integrated picture of ecosystem health that cannot be obtained from shoreline monitoring alone.