In 2024, scientists dyed Peter Lake blue with Aquashade to starve algae of light, but the water still turned green, and the team suspects repeated rain kept flushing the pigment out.

The lake is Peter Lake, a long-serving subject of one of ecology’s most patient experiments, and the person tipping pigment over the gunwale was Danny Szydlowski, a PhD candidate and CASC graduate fellow at the University of Wisconsin–Madison Center for Limnology, working with a colleague, Dat Ha. Their account of the season, published on the Midwest Climate Adaptation Science Center blog on 22 January 2025, reads less like a triumph than a puzzle: the dye went in, the fertiliser followed, and the water still bloomed.