White Gorgonian

On gently sloping rocky substrate, light reveals long white branches rising above the sediment. The white gorgonian tolerates well-lit sectors, and shallow colonies can harbor symbiotic microalgae within their tissues.

The association begins very early: its larvae also possess these symbionts, and experiments show that in light their activity helps larvae preserve part of their energy reserves. By slowly approaching the branches, another encounter can hide within the first.

A small white tritonia, Candiella odhneri, can blend with its substrate, consume its polyps, and deposit its spawn there. But the most worrying change is impossible to detect during a dive.

In shallow populations monitored in the northwestern Mediterranean, repeated marine heat waves have been associated with increased mortality, decreased recruitment, and a sharp increase in adult colonies that no longer reproduce. Female reproduction appears particularly affected in the studied populations.

Before the diver, however, some colonies remain, white and upright in the light: nothing in their silhouette necessarily reveals what several summers that were too warm have already changed inside.