The Mystery of Fish Deaths in a Foul Chartreuse Sea

This story originally appeared on Hakai and is part of the Climate Desk collaboration.

Dead fish were everywhere, speckling the beach near town and extending onto the surrounding coastline. The sheer magnitude of the October 2021 die-off, when hundreds, possibly thousands, of herring washed up, is what sticks in the minds of the residents of Kotzebue, Alaska. Fish were “literally all over the beaches,” says Bob Schaeffer, a fisherman and elder from the Qikiqtaġruŋmiut tribe.

Despite the dramatic deaths, there was no apparent culprit. “We have no idea what caused it,” says Alex Whiting, the environmental program director for the Native Village of Kotzebue. He wonders if the die-off was a symptom of a problem he’s had his eye on for the past 15 years: blooms of toxic cyanobacteria, sometimes called blue-green algae, that have become increasingly noticeable in the waters around this remote Alaska town.

Kotzebue sits about 40 kilometers north of the Arctic Circle, on Alaska’s western coastline. Before the Russian explorer Otto von Kotzebue had his name attached to the…