It’s that time of year again: the EPA’s floating science lab, the R/V Lake Guardian set sail for its annual summer tour of the Great Lakes. The vessel will spend a month cruising all five lakes — but don’t expect a beach playlist or sunbathing. This mission is strictly science.

According to the U.S. Environmental Protection Agency, the Lake Guardian’s summer survey is all about taking the pulse of the lakes when they’re at their warm-weather peak. That means collecting water samples and tiny aquatic organisms like plankton — “critical species in the lower food web,” as the EPA puts it.

Why the plankton obsession? Because these microscopic creatures help scientists track the health of the lakes’ ecosystems — especially when it comes to understanding how algal blooms and invasive species are shaking things up.

“Data gathered on the annual surveys enables EPA and partner agencies to assess how invasive species and algal blooms affect fisheries and water quality to better protect the Great Lakes for drinking water, fishing and recreation,” said the agency in a statement.

The summer is a strategic time to sample, as it’s when “warmer surface water overlays colder bottom water,” a layering that influences everything from oxygen levels to fish habitats. Scientists aboard will also gather data to improve satellite-based monitoring tools — a high-tech assist to this boots-on-deck (or rather, lifejacket-on-deck) operation.

Joining the EPA scientists are researchers from across the Great Lakes region, including Cornell University, University of Minnesota Duluth, Michigan Technological University, SUNY Buffalo State, and the Oak Ridge Institute for Science and Education.

The EPA has been running these sampling surveys since 1983, building what’s now the longest-running and most comprehensive data set on Great Lakes health. The R/V Lake Guardian itself is funded by the Great Lakes Restoration Initiative, a 2010 program aimed at protecting and restoring the world’s largest surface freshwater system.

So next time you’re gazing out at Lake Michigan or casting a line in Lake Erie, remember there’s a ship out there quietly working to keep your water clean, your fish plentiful, and your summer algae-free.