Using Artificial Reef Systems to Push Recovery of Diadema antillarum and Coral Reefs in the Caribbean

Abstract

In 1983, a water born pathogen spread through the Caribbean ocean severely decreasing the Di-adema antillarum, the Long Spined Sea Urchin, population. Diadema antillarum are herbivores that are responsible for consuming a majority of the macroalgae on coral reefs and therefore are considered a keystone species. Without them, the high growth rate of marcoalgae allow them to grow over coral reefs; blocking sunlight and nutrients from reaching coral. The result is a phase shift from complex coral dominated reefs to flat algae dominated reefs. Diadema antillarum recov-ery is crucial in order to reverse this phase shift. Low complexity reefs provide little to no refuge for juvenile Diadema and juvenile coral recruits from predators. In an attempt to push Diadema recovery, artificial reefs were placed in La Ensenada, a reef off the shore of Tela, Honduras. Each artificial reef consists of 8 breezeblocks and 30 artificial reefs were created. These breezeblocks provide reefs with the complexity needed to reintroduce Diadema and coral. The artificial reefs were first placed during the summer of 2015 and surveyed each year. This was the third year of artificial reef surveying. Surveying consisted of placing 10, 1x1m quadrats, 5 directly around the artificial reef and 5 slightly further, and recording macroinvertebrates, juvenile coral recruits and HAS score within each quadrat. From 2015 to 2016, only small increases in Diadema antillarum were found but along with the small increases in urchins, decreases in algae cover, and increases in coral cover and biodiversity provided some positive feedback from these artificial reefs. From 2016 to 2017, there has been a significant increase in Diadema populations, significant decreases in algae cover, and significant increases in coral cover and biodiversity. With this information, we hope to introduce artificial reefs as a cost effective conservation strategy to help restore Diadema antillarum populations which in turn will restore Caribbean coral reefs to be coral dominated.