Threatened Elkhorn coral

New research from the UM Rosenstiel School shows that threatened Elkhorn coral (Acropora palmata) faces an additional challenge in rebuilding its once thriving reefs. Published in the current issue of Molecular Ecology, the article finds that populations of Elkhorn coral are genetically distinct between eastern and western areas of the Caribbean, implying that exchange of larvae (i.e. immigration) is negligible between the two areas. This isolation may limit Elkhorn coral’s ability to re-colonize reefs where it has died off and suggests the need for local protections to facilitate new growth.

As recently as March 3rd, the NOAA-Fisheries Service proposed to protect elkhorn coral – one of two coral species native to Florida and the Caribbean that the Fisheries Service considered to be threatened under the federal Endangered Species Act (ESA). Both Elkhorn and its relative, Staghorn coral (A. cervicornis), have had 80-98 percent declines in their populations throughout Florida and Caribbean waters. These would be the first listings of any coral species as threatened or endangered under the ESA. The results of the study, which was sponsored by NOAA through its Coral Reef Conservation Program and by the Environmental Protection Agency through the National Center for Caribbean Coral Reef Research (NCORE) at the Rosenstiel School, will be considered in the upcoming design of regulatory protections under the ESA.

"Our findings indicate it may be more difficult than we originally thought to rebuild the Caribbean coral reefs that have declined so rapidly in the recent past," said Dr.Iliana B. Baums, lead author and postdoctoral associate at the Rosenstiel School. "The elkhorn coral releases larvae into the water column where they develop for several days to two weeks. During this time, they could be transported long distances by ocean currents and so connecting distant populations. However, we found that the corals' genetic material didn't travel very far. This limits its ability to cross breed and isolates certain areas. The Elkhorn coral is split into two populations that are so isolated they require protection and management on a more local scale to ensure their recovery."

Dr. Baums and Drs. Margaret W. Miller and Michael E. Hellberg, respectively from the NOAA-Fisheries Service and Louisiana State University developed five molecular markers to analyze the Elkhorn coral's immigration and isolation patterns – at a genetic level. Using these markers and mathematical analyses, they saw that populations of the imperiled reef-building Elkhorn coral were not interacting between the western and eastern Caribbean region. Also, some reefs received lots of immigrants from other reefs within their own region, while other reefs were primarily self-recruiting. This suggests that certain reefs play a more important role in connecting populations than others.

While coral reefs may seem like merely beautiful oceanic landscape, they are actually a world in themselves– providing food and shelter and sustaining an ecosystem of countless species that thrive on the coral-built structures. Additionally, coral reefs act as buffers, protecting coasts from significant storm activity, and it's their beauty that facilitates much of the tourism that sustains the Florida and Caribbean economies.

Unfortunately, both man-made and natural factors have played into coral reef destruction. Facing threats from El Nino, heat stress, disease, and hurricane wave forces to ship groundings, sediment runoff, and dynamite and chemical fishing, it’s not easy to be a coral reef. It has been reported that 20 percent of the world’s coral reefs have been effectively, and possibly permanently destroyed. Dr. Baums' research indicates the challenges to recovery may be more numerous than originally thought, highlighting the need for human intervention and protection.

Rosenstiel School is part of the University of Miami and, since its founding in the 1940s, has grown into one of the world’s premier marine and atmospheric research institutions.