Caribbean Sea-urchin Die-off

The long-spine black sea urchin (Diadema antillarum) used to be known to every Caribbean beach-walker, snorkeler, and scuba diver. It is ecologically significant: consuming bottom-growing algae contributes to the balance between stony corals and algae. Night divers see them graze more actively at night.

In 1983, the Caribbean saw a severe die-off of Diadema. There was some recovery, but to only a fraction of the previous population. Another die-off event began off St. Thomas, USVI, in January 2022, and by June, had spread to most of the Caribbean. The spread suggested an infectious cause. The loss of Diadema led to the marked degradation of several coral reefs.

A large multinational scientific team headed by Ian Hewson of Cornell identified the causative agent. It is a single-cell "scuticociliate" organism, about one four-hundredths of an inch long. No prevention or treatment is envisioned.

- Jeffrey D. Hubbard, M.D.

Hewson et al., Sci. Adv. 9, eadg3200 (2023) 19 April 2023 [https://www.science.org/doi/10.1126/sciadv.adg3200]