The mystery of fish deaths in a filthy Chartreuse sea -Dlight News

The mystery of fish deaths in a filthy Chartreuse sea

This story originally appeared in Hakai and is part of climatic table collaboration.

Dead fish were everywhere, dotting the beach near the town and spilling out onto the surrounding shoreline. The sheer magnitude of the October 2021 die-off, when hundreds, possibly thousands, of herring washed away, is what remains on the minds of residents of Kotzebue, Alaska. The fish were “literally all over the beaches,” says Bob Schaeffer, a fisherman and Qikiqtaġruŋmiut tribal elder.

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

Kotzebue is located about 40 kilometers north of the Arctic Circle, on the western coast of Alaska. Before Russian explorer Otto von Kotzebue named the place after him in the 19th century, the region was called Qikiqtaġruk, meaning “place that is almost an island.” One side of the 2-kilometer-long settlement is bordered by Kotzebue Sound, a branch of the Chukchi Sea, and the other by a lagoon. Planes, ships and four-wheeled vehicles are the main means of transportation. The only road out of town simply goes around the lagoon before re-entering.

Downtown, the Alaska Commercial Company sells foods that are popular in the lower 48, from cereal to apples to two-bite brownies, but the ocean is the real grocery store for many people in town. Alaska Natives, who make up about three-quarters of Kotzebue’s population, harvest hundreds of kilograms of food from the sea each year.

“We are ocean people,” Schaeffer tells me. The two of us are crammed into the small cabin of Schaeffer’s fishing boat in the daylight hours of a rainy September morning in 2022. We head toward a water monitoring device that has been moored in Kotzebue Sound all summer. At the bow, Ajit Subramaniam, a microbial oceanographer at Columbia University, New York, Whiting and Schaeffer’s son Vince have their noses tucked into turn-up collars to keep out the cold rain. We’re all there to collect a summer’s worth of information about the cyanobacteria that could be poisoning the fish that Schaeffer and many others depend on.

huge colonies of algae is nothing new and often beneficial. In the spring, for example, increased light and nutrient levels cause phytoplankton to flourish, creating a microbial soup that feeds fish and invertebrates. But unlike many forms of algae, cyanobacteria can be dangerous. Some species can produce cyanotoxins that cause liver or neurological damage, and perhaps even cancer, in humans and other animals.

Many communities have fallen out of favor with cyanobacteria. Although many cyanobacteria can survive in the marine environment, freshwater blooms tend to attract more attention, and their effects can spill over into brackish environments when streams and rivers carry them out to sea. In East Africa, for example, blooms in Lake Victoria are blamed for massive fish kills. People can suffer, too: In one extreme case in 1996, 26 patients died after receiving treatment at a Brazilian hemodialysis center, and an investigation found cyanotoxins in the clinic’s water supply. More often, people who are exposed experience fever, headaches, or vomiting.

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