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A new study found that extreme heat and drought turned an Amazon lake into water hotter than a jacuzzi, killing hundreds of dolphins and exposing the growing toll of climate change on tropical ecosystems.

Researchers, led by hydrologist Ayan Fleischmann of Brazil’s Mamiraua Institute for Sustainable Development, reported that in September 2023, water temperatures in Lake Tefe soared to 105.8 °F (41 °C) -- “hotter than most spa baths.”

“You couldn’t put your finger in the water,” Fleischmann said, according to CBS News.

He noted the “psychological impact” of seeing carcasses of pink dolphins and tucuxis, both endangered species.

The findings, published Thursday in Science and reported by CBS News, reveal that five of 10 Amazon lakes studied experienced unprecedented daytime temperatures above 37 °C, with Lake Tefe’s surface area shrinking by 75%.

Modeling showed that strong solar radiation, shallow depths and weak winds combined to trap heat in the stagnant waters.

According to WWF Brazil, 153 dolphins were found dead in one week in September 2023.

“The climate emergency is here, there is no doubt about it,” said Fleischmann, urging long-term lake monitoring and inclusion of Indigenous and riverine communities in climate adaptation efforts.

The research coincides with the opening of the UN COP30 climate summit in Brazil, underscoring how warming waters are already upending the Amazon’s delicate balance.

“Rising river water temperatures can have significant and often detrimental implications for aquatic life,” warned David Hannah of the University of Birmingham, a co-author of a related study.