The historic drought and heat wave that hit the Amazon in 2023 caused extreme warming and unprecedented in its waters, with devastating consequences that we are seeing today. A new study published in Science details how water temperatures in key lakes reached lethal levels, causing high mortality in fish and especially river dolphins.
Very high temperatures. A priori we may think that heat waves just as they come will go away without leaving any consequences. But the reality is very different, since in the Amazon, of the ten lakes that were monitored, five exceeded 37ºC during the day and there was one that reached 41ºC as if it were a spa pool.
This extreme heat wasn’t just skin deep; It penetrated the entire water column, approximately 2 meters deep, eliminating any fresh refuge for aquatic life. It was literally left uninhabited.
Epicenter of the tragedy. Lake Tefé, which is normally more than 7 km wide, became the focus of national and international attention after its surface area will be reduced by 75% between September and October 2023. It is literally a consumption never seen before that surprised the inhabitants of the area and also the animals.
This drastic reduction in water coincided with a “massive and unprecedented mortality” of river dolphins. In a short interval, 209 dolphin carcasses were found (both from the Amazon River and Tucuxi). And precisely, the study points out that only on September 28, 2023, when temperatures reached 39.5 °C for the first timeseventy dolphin carcasses were found.
The researchers also observed extreme daily temperature variation of up to 13.3°C, meaning the water went from hot tub-like heat during the day to drastically cooling at night. completely altering the conditions of the system. And living there becomes really complicated.
What caused this extreme heat. The study used models to identify the culprits behind this warming. It was a “perfect storm” of factors that coincided such as high solar radiation due to completely clear skies that could not stop the sun. But the reduced depth of the water or the low wind speed also intervened, which generated less cooling due to evaporation.
A long term problem. While the 2023 event was extreme, it is not an isolated incident. Study reveals worrying long-term warming trend in region, Based on satellite estimates, between 1990 and 2023, the lakes in the Amazon region have experienced a temperature increase of 0.6 degrees per decade.
A great ecological crisis. The impact was not limited to the dolphins. The study also documents significant fish mortality. All because of the fact that they have a fairly narrow temperature tolerance range, meaning that the moment there is an increase, even a slight one, in temperature, they are finished off.
For human populations, the consequences were equally serious. The drought and extreme heat managed to isolate thousands of people in riverside communities, leaving them without adequate access to food, drinking water and medicine because maritime transport is also severely affected.
Images | Natalia Pedraza
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