WILLEMSTAD – Scientists are increasingly using herbivorous invertebrates such as sea urchins and crabs to combat algae overgrowth on coral reefs. These animals consume the algae that suffocate coral and, under the right conditions, have proven to be a valuable addition to existing reef restoration strategies. This innovative approach could also hold promise for the Dutch Caribbean islands—though significant challenges remain.
According to a new study published in the journal Restoration Ecology, many Caribbean reefs have shifted from vibrant coral ecosystems to algae-dominated environments over the past few decades. This transition is largely due to the mass die-offs of the sea urchin species Diadema antillarum in the 1980s and again in 2022, as well as the overfishing of parrotfish, which play a key role in keeping algae in check.
The research, conducted by scientists from Antigua, the Netherlands, Mexico, and the United States, focused on four types of algae-eating invertebrates: three sea urchin species and one large crab species (Maguimithrax spinosissimus). The crab stood out for its effectiveness, consuming types of algae that other species avoid and contributing to an increase in young corals and reef fish.
Scaling Up Remains a Challenge
While the results are promising, the study notes that scaling up this method is difficult. Rearing larvae and growing young animals is technically demanding and expensive. Additionally, many of the animals released into the wild either die early or leave the reef, limiting the ecological impact. Current monitoring methods such as tagging and underwater cameras are not yet reliable enough to fully measure success.
For islands like Curaçao, Bonaire, and Saba—where active coral restoration programs are underway—the use of native sea urchins and crabs offers new possibilities. However, researchers emphasize that investment in local breeding programs, genetic research, and long-term monitoring is crucial to making this approach both effective and sustainable.