With the brassy stutter of a rusty wheel whizzing downhill, an American coot announces itself from the shores of Pinto Lake as Kendra Hayashi scoops water from the side of the dock. Today, the sample in her glass bottle looks mostly clear, as does the liquid buoying the bird. But three weeks earlier, she says, the lake’s surface bloomed with potentially toxic algae. The coots and mallards didn’t seem to notice. … Hayashi manages a lab at UC Santa Cruz that monitors microcystin—a toxin produced by algae in the genus Microcystis—in Watsonville’s Pinto Lake. Though it once had among the highest measured levels of microcystin of any freshwater body on earth, the lake hasn’t had a toxic event in years, thanks to local cleanup efforts.