MARSEILLE: In the temperate shallows of the Mediterranean, once-vibrant red and purple coral forests that provide a crucial haven for biodiversity now stand bleached and brittle, transformed into skeletons by record summer temperatures, scientists say.

Holding naked branches of gorgonian coral, Tristan Estaque of marine conservation group Septentrion Environnement is returning despondent from an exploratory dive off the coast of Marseille in southern France. “It is heartbreaking, the deterioration is so fast,” he said. Dive surveys just two months earlier found an intact landscape, lush with violet-fringed fans of gorgonian coral.

Now it is a “ghost forest”, says Estaque, with the majestic fans largely bare of living tissue.

“You have to imagine a tree where there are no more leaves, no more bark.”

Fragile forests

Gorgonian corals, which have flexible skeletons encrusted with polyps, are found across the planet. Those found in the Mediterranean are said to create “forests”, sheltering a huge array of species. But they are acutely vulnerable to human activities.

Fishing nets, anchors and careless divers can rip their delicate structures, while exposure to continuous and intense heat can be lethal. Marine heatwaves are becoming more common, according to a report this year by UN climate experts.

This summer a major marine heatwave hit the western Mediterranean, with water up to five degrees Celsius (41 degrees Fahrenheit) hotter than normal, according to Mercator Ocean International, the organisation that runs the European ocean monitoring service. In some places water reached 30C.

Recent Septentrion Environnement surveys have shown that between 70 and 90 percent of the red gorgonian population in the 10 to 20-metre zone off Marseille have since died.

Published in Dawn, September 28th, 2022