The Vanishing Diadema: A Parasite-Driven Reef Crisis Unfolds

Marine columnist Gary Rose details the long-spined black sea urchin (Diadema antillarum) collapse seen starting in 1983—linked to Saharan dust, pollutants and massive coral bleaching—and the more recent 2023 dies-off caused by a ciliates parasite, Philaster apodigitiformis, which decimated Caribbean urchin populations and left reefs vulnerable to algae overgrowth; scientists have confirmed the parasite’s role and are pursuing ways to protect and restore urchin numbers to revive reef health.