Caribbean corals have been warming for more than a century

Analysis of historical temperature records in the Greater Caribbean region, which includes the Gulf of Mexico, has detected an upward trend in sea temperature since 1915 that is affecting the region’s coral ecosystem. If this rate continues, the reefs could warm up by 1.5°C by 2100, jeopardizing their survival.

So far, several studies have documented drastic changes in coral reef ecosystems around the world, especially in the Caribbean in particular, due to increased water temperatures as a result of climate change.

One of the reported effects is massive coral bleaching, a process of stress in which they experience the expulsion or death of their symbiotic protozoan algae called zooxanthellae, which give them their color and provide them with food. This ultimately causes the death of the animal.

As bleaching events become more frequent, we are seeing a general decline in coral cover across the ecosystem“, explains Colleen Bove, marine ecophysiologist at the University of North Carolina at Chapel Hill (USA) and first author of a study published in the journal PLoS Climate.

To find out how long this process has been going on, the research team analyzed sea temperature records in the Greater Caribbean region – which includes the Gulf of Mexico – over the past 150 years, and determined that there is an upward trend that has affected the coral ecosystem.

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The researchers created a database of 5,326 coral reefs located in this area, which they divided into eight distinct sub-regions. They then used three historical records of sea surface temperature, collected both by satellite and on the ground, to assess the warming process from 1871 to 2020.

The analysis showed that throughout the study area, Caribbean coral reefs have experienced a temperature increase since 1915 of between 0.5 and 1ºC. In four of the eight regions, warming began even earlier, in the second half of the 19th century.

Recorded data show that the sea temperature increase had a stable phase in the middle of the last century, only to pick up again in the 1980s and 1990s.

On average, Caribbean reef temperatures have changed by 0.18°C per decade since then, suggesting that if this rate continues, ecosystems could warm by 1.5°C by 2100.warns Bové.

more heat waves

On the left, the rate of warming of the area studied over the period 1981-2018. On the right, the frequency of sea heat waves. / Coleen Bove et al.

The team also looked at marine heat waves – short periods of unusually high ocean temperatures – to find that these events are increasing in frequency and duration in the Caribbean.

Reefs now experience an average of five such events a year, down from an average of once a year in the 1980s.

Drastic temperature changes are a stressor that can lead to coral bleaching and death.

The extinction of corals in the Gulf of Mexico and the Caribbean would mean the loss of the ecosystem that uses the reefs as habitat and would have enormous consequences for the hundreds of millions of human beings who depend on these reefs for food. and earn income from fishing.“, concludes Bové.

Reference:

Bove C, Mudge L, et al“A century of warming on Caribbean reefs”. PLoS Climate2022.

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