Diadema Response Network: Concerns for Diadema – your help is needed

Newsletter published: March 29, 2022. (Para texto en español – haga clic aquí)

The Caribbean may be facing another widespread die-off of sea urchins. Diadema antillarum, also known as the long-spined sea urchin, is one of the most important herbivores on Caribbean coral reefs, removing algae and maintaining open space for coral growth.

In mid-February 2022, we first learned of extensive Diadema die-offs close to Charlotte Amalie Harbor in St. Thomas, U.S. Virgin Islands (USVI). Within a month, additional mortality events had been independently observed elsewhere in St. Thomas plus nearby St. John, as well as Saba, St. Eustatius, Dominica, Jamaica, St. Vincent, and perhaps other islands. See map below.

Diadema previously experienced a massive die-off throughout the Caribbean in the early 1980s. Sampling at the time was inadequate to determine the cause of their demise. Few Diadema populations have since fully recovered, resulting in algal-dominated states on many of the region’s reefs.

While we do not know what is causing these dispersed die-offs, the speed at which large numbers of sick urchins are now dying on affected reefs resembles the mass mortality event of four decades ago. We worry that a real crisis is developing in the Caribbean, where stony coral tissue loss disease (SCTLD) has already caused widespread coral losses affecting about 34 coral species in 20 countries/territories.

Signs of sick and dying urchins include detaching from substrate through loss of control of their tube feet, followed by loss of spines, tissue loss and rapid death.

Healthy urchin
Photo credit: K. Marks
Sick, dying urchin
Photo credit: Kimani Kitson-Walters

Diadema Response Network

A region-wide collaboration–the Diadema Response Network–has quickly formed to track and try to understand the cause of this recent die-off of Diadema (and possibly other sea urchins). We need your help in reporting healthy, sick or dead urchins and in collecting samples to search for the causation of the die-off.

To find out how to help, read the full newsletter here: https://mailchi.mp/agrra/new-diadema-die-offs-in-caribbean , and visit the Diadema Response Network page: https://www.agrra.org/sea-urchin-die-off/

Contact us on Diadema@agrra.org for questions and more information related to Diadema.