Scientists discover cause of sea urchin die-offs in the Caribbean: a protozoan parasite

Researcher swims in the ocean with scuba gear to study long-spined sea urchins.
Dr. Don Behringer studies long-spined sea urchins to understand why they began quickly dying in large numbers.

The long-spined sea urchin Diadema antillarum is a keystone species. Coral reefs rely on healthy sea urchins to eat algae so coral can thrive. Healthy coral means healthy fish, and their positive impacts continue up the food chain.

In early 2022, long-spined sea urchins in St. Thomas began to quickly die in large numbers. Scientists rushed in to find the cause and have discovered that a microscopic parasite swarms the body and spines of the urchins, eating them alive.

The culprit, a microscopic organism called a scuticociliate, appears most similar to Philaster apodigitiformis, a type of protozoan parasite. It began decimating sea urchin populations around the Caribbean, and within days of being symptomatic, urchins were dying. In a matter of months, losses were reported in nine more locations across the Caribbean, including off the Florida coast.

“The research team was still processing samples from the last site where a die-off occurred when we would get calls about a new location with dying urchins,” said Don Behringer, UF/IFAS professor of marine disease ecology and lead on a National Science Foundation RAPID grant that made the work possible. Behringer is also a member of the UF Emerging Pathogens Institute. “It only took a couple weeks for the majority of the long-spined urchins to be wiped out at a specific site. Rapid-response funding like this allows us to go to locations to sample and assess environmental conditions quickly and learn from it.”

This article was originally written by Tory Moore for UF/IFAS. To read the full article, visit the blog.