Why are Atlantic corals so endangered?

While the vast majority of reefs are found in the Indian and Pacific Oceansabout 10% are in the Atlantic. These corals are very distinct from their parents, having been separated from other corals by the joining of North and South America more than three million years ago.

A total of 85 species of shallow-water corals live in the Atlantic, with the most important hotspots found in the Caribbean and off the coast of Brazil. As co-author of the study Dr Nadia Santodomingo explains that the limited ability of these species to respond to the threats they face means these reefs are more vulnerable to collapse.

“Atlantic corals have been hit hardest by reef decline,” says Nadia, curator of cnidarian fossils at the Natural History Museum. “They face a perfect storm of threats, of which climate change is just one part. »

“These corals are significantly affected by overfishing, pollution and coral diseases which are more prevalent in the Atlantic than in other regions. As a result, I was not surprised to see the results of the IUCN assessment.

The disease has perhaps had the most dramatic impact on Atlantic corals, devastating not only the corals of the region but also the animals on which they depend. An unknown disease is suspected to have killed up to 98% of the Caribbean’s long-spined sea urchins in the 1980s, meaning these grazers were unable to stop the algae from dominating many reefs.

New diseases continue to emerge, with stony coral tissue loss disease first detected in 2014. The disease spread rapidly across the Caribbean, killing up to 94% of all infected corals.

Rising temperatures also pose a growing threat, with bleaching just the tip of the iceberg. Higher levels of carbon dioxide make the ocean more acidic, making it harder for corals to grow their calcium carbonate skeletons. Climate change is also linked to an increase in the number of hurricanes in the region, which wipe out centuries-old reefs within hours.

While the PLOS One study raises many reasons for concern, it also notes some reasons for hope. After the devastating decline of the 1970s and 1980s, researchers found that the decline in coral cover in the Atlantic appears to be decreasing.

To support these green shoots of recovery, additional research must be conducted to understand how corals can adapt to the challenges they face. As Dr Beth Polidoro, co-lead author of the paper, explains, this must go hand in hand with urgent action to combat climate change and other threats to corals.

“We need to drastically reduce greenhouse gas emissions while taking steps to address local threats if we want to give coral reefs a chance of surviving,” he says. Dr. Beth Polidoroco-senior author of the article. “By acting now, we can slow the rate of ocean warming and expanding the window of opportunity for corals to potentially adapt and survive in the long term.