Written by Sofia Perez

Edited by Matthew Tietbohl

Most people associate sea urchins with two things: sushi and painful puncture wounds. In sushi, they are referred to as uni and boast a buttery sweet taste. On the contrary lies their less-sweet reputation as one of the things in the ocean you don’t want to step on. If you are one of the unfortunate individuals who has experienced this, you will know that their spines contain irritant toxins and leave behind an unwanted black tattoo on your skin. Naturally, this is quite unpleasant. Yet besides these two encounters, what are urchins and do they amount to more than just sushi and surprise tattoos?

The answer? Yes. In fact, sea urchin are more important than they look. Mostly encountered on rocky shores, beaches, and coral reefs, these slow-moving spiky black creatures are hugely valuable to their ecosystems. In fact, they can be key organisms in determining their community’s composition and appearance. Why? They provide an extremely important service: eating a lot. In fact, if you invited all the species present in a coral reef to a marine Thanksgiving dinner, urchins would eat the majority of all macroalgae served. Not only this, but they would eat it faster than anyone else. This is important because it prevents macroalgae from overtaking corals and depleting reefs. That is definitely something to be grateful for!

It is this insatiable appetite that makes urchins so powerful in determining the health of reef ecosystems. By eating the algae growing surfaces and the decaying matter in sediments, these unassuming marine janitors are creating a more suitable environment for other animals who could inhabit the reef when it’s healthier. On the other hand, the ravenous appetite of urchins can also endanger ecosystems like kelp forests, but that won’t be discussed here at length. 

So now let’s imagine what would happen if we introduced these urchins to a reef. Recently, researchers at the Florida Aquarium, University of Florida, and Florida Fish & Wildlife Conservation Commission did just this. They successfully raised and released about 200 long-spined sea urchins(Diadema antillarum) off the coast of Florida. The idea is that they will play a role in saving degraded reefs by eating invasive algae. With a diameter of about 50cm, they move slowly, inching along with only their spines. Nonetheless, they are ready for action. They don’t know it, but their presence is the first step toward repopulating abandoned reefs. Now let’s take a step back. Once upon a time, Diadema antillarum was common throughout tropical areas of the Indian & Atlantic Oceans. They inhabited ecosystems from the shoreline to depths of 70m and deeper in Australia. Not only this, but as a proud member of the echinoderm family, which includes starfish, sand dollars, and sea cucumbers, they are also dear to those of us who appreciate radial symmetry. They lived a simple symmetrical life, with a central mouth on their underside and an anus on the upper surface.

Then came the 1980s. At this time in the Caribbean, long-spined urchins were almost completely wiped out due to an unknown disease. After this, only about 7% of the population was left. This was, and still is a tragedy. Long-spined sea urchins still haven’t fully recovered. Yet the impacts of such an event stretch beyond just sea urchins. They also hurt reefs, and when reefs lose such an important helper, all the animals relying on them suffer too. 

It is for this reason that researchers at the Florida Aquarium and University of Florida have been looking into ways of raising urchins and other grazers in order to help reefs recover. In addition to this, they research and breed dozens of coral species found along the 360-mile stretch from Dry Tortugas to Port St. Lucie. The goal is to restore coral populations with diverse and resilient offspring that can handle stressors like climate change, disease, etc. 

As part of this mission, the group raised 200 urchins over six and a half months then released them at various sites in the Florida Keys. The project is considered the largest restocking effort in the last twenty years and aims to understand better how to successfully transport, outplant, and monitor sea urchins. 

All in all, the battle to defend coral reefs is an ongoing struggle. At times it might even feel hopeless. Nonetheless, at times like these we can all be grateful to have such helpful marine custodians on our side. 

Bibliography

“Florida Aquarium Researchers Succeed in Largest Release of Hatchery-Raised Long-Spined Sea Urchins.” The Florida Aquarium, 15 Dec. 2021, http://www.flaquarium.org/press-room/florida-aquarium-researchers-succeed-in-largest-release-of-hatchery-raised-long-spined-sea-urchins/. Accessed 9 Jan. 2022.

“Florida Relies on Sea Urchins to Restore Coral Reefs – La Prensa Latina Media.” La Prensa Latina Media, 17 Dec. 2021, http://www.laprensalatina.com/florida-relies-on-sea-urchins-to-restore-coral-reefs/. Accessed 9 Jan. 2022.

“Long-Spined Sea Urchin, Diadema Antillarum.” Www.thecephalopodpage.org, http://www.thecephalopodpage.org/MarineInvertebrateZoology/Diademaantillarum.html. Accessed 9 Jan. 2022.Montgomery, Ben. “Florida Sea Urchins to the Reefs’ Rescue.” Axios, Axios Tampa Bay, 5 Jan. 2022, http://www.axios.com/local/tampa-bay/2022/01/05/florida-sea-urchins-to-the-reefs-rescue. Accessed 9 Jan. 2022.

News, Opening Hours 10am-5pmFree General EntryClosed Christmas Day Address 1 William StreetSydney NSW 2010 Australia Phone +61 2 9320 6000 www australian museum Copyright © 2022 The Australian Museum ABN 85 407 224 698 View Museum. “Long-Spined Sea Urchin.” The Australian Museum, 18 Dec. 2020, australian.museum/learn/animals/sea-stars/invertebrates-collection-long-spined-sea-urchin/. Accessed 9 Jan. 2022.

Upham, Valeska. “The Importance of Sea Urchins.” Oceanbites, 6 Apr. 2016, oceanbites.org/the-importance-of-sea-urchins/. Accessed 6 Dec. 2019.