Researcher Tom Wijers with a sea urchin.
ROTTERDAM--The sea urchin Diadema antillarum has been cultivated at Van Hall Larenstein University of Applied Sciences HVHL in Leeuwarden in the Netherlands to help restore the coral reefs around Saba and St. Eustatius. The first young urchins bred in the Frisian capital Leeuwarden were released on Wednesday, March 24, to the Rotterdam Diergaarde Blijdorp zoo. The ultimate goal is to also breed this species in Saba to give the sea urchin populations there a helping hand.
The sea urchins keep algae growth under control, giving corals more room to grow. During this project, researchers worked closely with students of the Coastal and Marine Management programme.
Diadema antillarum sea urchins were the main grazers of Caribbean coral reefs until over 95 per cent were killed by an unknown disease in 1983. Without sea urchins grazing, algae became the dominant group on the coral reef, outcompeting coral.
Today, nearly 40 years after their mass death, sea urchins have still not recovered. HVHL is working with the RAAK PRO Diadema 2019-2023 project, along with project partners for the restoration of this species in Saba and Statia.
For the past 40 years, researchers have been trying to breed diadema urchins in captivity, but unfortunately have only had limited success.
Breeding has been found to be very difficult. Larvae of this type of sea urchin float along sea currents for the first 50 days of their life and are sensitive to water quality and nutrient availability. However, in 2020 researchers and students from HVHL managed to develop a method for stable and consistent breeding of young diadema.
As it is difficult to transport these animals on a large scale to Saba or Statia, the first group of young urchins found a nice new home in the Rotterdam Zoo. The next step will be to breed urchins in Saba so that they can be released into the wild, strengthening the populations and helping to restore the coral reef.
