Black coral

Photo: Hexacorallians of the World · CC BY-NC-SA

Black corals are not true reef-building corals but rather colonial cnidarians related to sea anemones. Their skeleton — which is actually dark brown or black — was historically harvested for jewelry, driving populations on shallow Caribbean walls to near-extinction. At Basse-Terre the wall's exposure to upwelling and cooler temperatures allows black coral to grow at unusually shallow depths compared to most Caribbean sites. Individual colonies grow extremely slowly — decades for a colony of modest size — making them sensitive to any physical disturbance.