Amazon Lakes Reached 105 Degrees, Killing Dolphins and Fish in Extreme Heat Wave

A new study reveals that during the 2023 heat wave and drought in the Amazon, some lakes reached temperatures hotter than those recommended for hot tubs — exceeding 105 degrees Fahrenheit. The extreme conditions turned the lakes into what researchers called “shallow, simmering basins,” causing mass die-offs of endangered dolphins and fish.

Scientists in Brazil analyzed satellite data from 10 Amazon lakes during the record-breaking heat and drought in September and October 2023. They found that daytime temperatures in half the lakes rose above 98 degrees Fahrenheit, far beyond the normal range of about 86 degrees.

At Lake Tefé, in northwestern Brazil, temperatures climbed to 105.8 degrees Fahrenheit — surpassing the U.S. Centers for Disease Control and Prevention’s recommended maximum for hot tubs. The heat extended more than six feet below the surface, leaving no cool refuge for aquatic life.

Ayan Fleischmann, a hydrologist at the Mamirauá Institute for Sustainable Development and one of the study’s authors, said such extreme temperatures are likely unprecedented. Lake Tefé’s surface area shrank by 75%, and Lake Badajós shrunk by 92%. The resulting oxygen loss and heat exposure proved fatal for hundreds of Amazon river and tucuxi dolphins, as well as thousands of fish.

More than 200 dolphin carcasses were found in Lake Tefé during the peak of the heat wave. Researchers believe the heat may have affected the animals’ brains, preventing them from escaping to cooler waters.

The impact also devastated local communities that rely on the lakes for food, water, and transportation. “When aquatic ecosystems are disrupted, Amazonian communities are disrupted,” Fleischmann said.

The study attributes the extreme heating to a combination of factors: record drought, murky waters absorbing more sunlight, intense solar radiation, and weak winds that limited cooling.

Researchers also examined 30 years of data from 24 lakes and found that surface water temperatures have increased by about 1 degree Fahrenheit per decade. “Amazon lakes are facing a long-term warming process, likely associated with climate change and global warming,” Fleischmann said.

Credit: CNN Newsource

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