die off

The Diadema RAAK Project is a collaborative effort between University of Applied Sciences Van Hall Larenstein, Wageningen Marine Research and Wageningen University, STENAPA, Saba Conservation Foundation, Caribbean Netherlands Science Institute, University of Applied Sciences HZ, ISER Caribe, Wortel Product Design en Golden Rock Dive Center and is funded by Dutch Research Council (NWO). 

This project is working to improve local populations of long-spined sea urchins around Saba and St. Eustatius by collecting larva from the reef and allowing specimens to mature in a lab before being returned to the wild. Culturing Diadema can provide a number of benefits, including the ability to restock reefs which don’t have a natural larvae supply yet and allowing scientists to study the larval development and settlement cues. The results can consequently be used to develop new and more effective restoration methods.

In april 2022, the Dutch Caribbean Nature Alliance (DCNA), together with the University of Applied Sciences Van Hall Larenstein, hosted a sea urchin (Diadema Antillarum) restoration workshop on Saba. During the workshop experts and representatives from the Dutch Caribbean and Jamaica came together to join forces towards coral reef restoration. This workshop helped 21 coral experts from the Caribbean region and more than 65 online attendants, to obtain a comprehensive view of the overall situation of the Diadema sea urchin in the Caribbean, including the current die-off events and restoration techniques. Throughout the workshop important discussions took place to determine the next steps needed to mitigate the loss of Diadema sea urchins on a regional scale.

Presentation Overviews

2022 Diadema Die-off

Presenter: Alwin Hylkema (Van Hall Larenstein)

The first session covers the current status of Diadema populations within the Dutch Caribbean as well as an update on the current Diadema die-off events, scale, symptoms, treatments and update.  Put in the context of restoration, this presentation stressed the importance of RAAK Pro Diadema project and how it can assist in natural recoveries within Caribbean populations.

Introduction on Diadema Restoration

Presenter: Alwin Hylkema (Van Hall Larenstein)

This portion of the workshop introduced Diadema restoration and the various approaches to restore this important herbivore within the Caribbean.

Diadema Cultivation

Presenter: Tom Wijers (Van Hall Larenstein)

There are several restoration methods, most of which are dependent on natural larvae supply within the water (translocation, settler collection and assisted natural recovery).  However, for locations lacking adequate natural larvae supply, its possible to cultivate Diadema larvae from gametes to juveniles.  This presentation covers this process and explores its potential within the Caribbean.

The Diadema workshop was funded by the Ministry of Agriculture, Nature and Food Quality (LNV) as a support to the Nature and Environmental Policy Plan for the BES-islands, the Dutch Postcode Lottery and SIA, part of the Dutch Research Council (NWO).

Special Diadema BioNews Edition Navigation

• Introduction
• Background and Current State
• Restoration Efforts
• What you can do to help

As previously mentioned, a new wave of long-spiced sea urchins (Diadema antillarum) die-offs are happening throughout the Caribbean, including reports from the northern three islands of the Dutch Caribbean.

In mid-February 2022, the first reports of extensive Diadema die-offs came in from St. Thomas of the U.S. Virgin Islands. Within a month, additional mortality events had been independently observed on Saba, St. Eustatius, Dominica, Jamaica, St. Vincent. On St Maarten, Diadema loss has been recorded on the dive sites Little Bay (fort Amsterdam), Frenchman’s Reef and Cowboy Reef (Indigo Bay). In Curaçao, the first sightings of diseased sea urchins were reported in early June.  Two weeks later, more than 90% of the surveyed populations had disappeared.

On March 14th, 2022, St. Eustatius’ STENAPA was alerted by dive shops of a significant number of dead long-spined sea urchins in the artificial harbor area.  After conducting a survey, it was determined that 44% of the urchins were dead and 6% appeared to be sick, leaving only half the population in a healthy state.  The sick urchins were unable to stay attached to the substrate and had very minimal spine movement.

The video below was taken on St. Eustatius in March of 2022 by Kitmani Kitson-Walters (CNSI) and shows a number of sick and dying urchins across the seafloor.

A collaborative region-wide effort – 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).

Special Diadema BioNews Edition Navigation

• Introduction
• Background and Current State
• Restoration Efforts
• What you can do to help