Scientists Study Great Lakes Health Aboard Lake Guardian

Inside the EPA’s 24/7 Great Lakes Research Vessel Operations

Life aboard the Lake Guardian runs in continuous shifts to maximize data collection across vast freshwater bodies that rival oceans in scale. According to Anne Scofield, a physical scientist at the EPA’s Great Lakes National Program Office, researchers work from 4:00 p.m. to 4:00 a.m. or vice versa. The vessel’s annual summer surveys take roughly a month to traverse all five lakes, while separate springtime monitoring occurs when water temperatures hit their lowest points.

Since April, the Lake Guardian has logged more than 12,500 nautical miles—equivalent to roughly 23,150 kilometers—and sampled 282 locations, according to EPA data. The multiagency-funded vessel relies on support from the Great Lakes Restoration Initiative, a fund launched in 2010 to protect the world’s largest surface freshwater ecosystem. Beyond EPA personnel, the ship regularly hosts researchers from institutions such as Cornell University, the University of Michigan, and the University of Minnesota-Duluth.

Tracking Lower Food Web Shifts and Invasive Species

During nightly sampling operations, crew members deploy specialized nets to capture mysids, which are the Great Lakes’ largest zooplankton and a vital food source for local fish populations. According to Scofield, recent summer surveys in Lake Michigan revealed unusually low concentrations of mysids, particularly within the southern basin. This observation mirrors a broader downward trend in mysid populations since the early 2000s, likely driven by falling phytoplankton levels and clearer water limiting habitat for light-sensitive organisms.

The onboard scientific team also collects water samples to track nutrient concentrations, algae, and phytoplankton, alongside physical metrics like turbidity, pH, and clarity. By drilling sediment cores, researchers reconstruct how chemical contaminants have shifted over decades. In addition, the vessel conducts targeted lake bed invertebrate studies utilizing underwater video cameras and sediment grabs to map the spread of invasive quagga mussels. Ongoing 2026 surveys in Lake Superior focus heavily on mapping the distribution of organisms like Diporeia, a crucial crustacean food source for fish.

How Resource Managers Use Lake Guardian Data

Data gathered by the Lake Guardian feed directly into the triennial State of the Great Lakes reports, published jointly by the EPA and the Canada Water Agency under the 1972 Great Lakes Water Quality Agreement. State and federal resource managers rely on these foundational datasets to make decisions. For instance, Vic Santucci, Lake Michigan program manager in the Division of Fisheries at the Illinois Department of Natural Resources, utilized historical report data regarding declining lake productivity and invasive mussel expansion to adjust salmon and trout stocking rates.

“Long-term datasets are crucial for managing lakes the size of the Great Lakes,” Santucci wrote in an email reported by Eos staff writer Grace van Deelen. Fisheries managers continually consult these biological metrics to understand fluctuations in the lower food web and adjust harvest or stocking policies accordingly.

Frequently Asked Questions

What is the primary mission of the research vessel Lake Guardian?

The Lake Guardian conducts 24/7 water quality and food-web monitoring across all five Great Lakes to assess ecosystem stressors, track invasive species, and support regional fisheries management.

How long has the EPA run these Great Lakes surveys?

According to the EPA, the agency has conducted biannual sampling surveys in the spring and summer since 1983, creating the longest-running extensive monitoring dataset for the region.

Who funds the operations of the Lake Guardian?

The vessel’s annual monitoring surveys are funded by the Great Lakes Restoration Initiative, a multiagency fund established in 2010.

How do state agencies use the data collected on board?

State natural resource managers use data from the EPA’s State of the Great Lakes reports to make decisions regarding fish stocking, water quality protection, and ecosystem restoration.