The new RAAK PRO Diadema project aims to restore the population of the long-spined sea urchin populations (Diadem antillanim) on the coral reefs around Saba and St. Eustatius. This particular urchin was once the most important herbivore on Caribbean coral reefs until more than 95 per cent of the sea urchins died in 1983 due to an unknown disease.
Without their grazing the algae flourished, which then smothered the corals as well as prevented baby corals from finding clear surfaces to start growing on. This changed the coral reefs to algal beds.
More than 35 years later, these long-spined sea urchins are still very rare and only sometimes abundant in shallow waters such as harbours.
They are seldom seen on the deeper coral reef. Worldwide, coral reefs face many threats that are difficult to tackle locally, such as global warming and ocean water becoming more and more acidic due to absorption of carbon dioxide. This makes it even more urgent to remove as many local threats as possible.
Increasing the number of sea urchins to numbers that existed before the die-off will successfully remove the overgrowing algae and will make the reefs more resilient to the other threats they face.
To do this, University of Applied Sciences Van Hall Larenstein, St. Eustatius National Parks STENAPA Foundation, Saba Conservation Foundation, Wageningen Marine Research, Wageningen University, Caribbean Netherlands Science Institute (CNSI), University of Applied Sciences HZ, Institute for Socio-Ecological Research ISER Caribe, Wortel Product Design and Golden Rock Dive Center are working together in the new RAAK PRO Diadema project. The project is partly funded by the Dutch Organization for Scientific Research NWO and will run for four years starting this month.
The first step to be taken by this team will be to find out why the populations on most reefs have not recovered. Initial tests have found a high abundance of very small juvenile sea urchins. Adult longspined sea urchins were, however, absent on the reefs.
The presence of these juveniles makes one thing clear — that there is potential for the population to recover as needed. Therefore, the research will focus on the early stages in the lifecycle of these sea urchins.
The ultimate goal is to develop a new method to maximize settlement and survival of larvae and juveniles and, by doing this, restore the populations of this important herbivore, so that the sea urchins will, once more, graze away the algae and aid in the recovery of Saba’s and Statia’s coral reefs.
The Daily Herald.