Hope for the Great Elkhorn Coral

Hope for the Great Elkhorn CoralPart 3 in The Nature Conservancy Series
by Kemit-Amon Lewis, Coral Conservation Manager
Coral reefs are vital to our Caribbean way of life! They provide shoreline protection to coastal communities, create opportunities for recreation, and are critical developmental habitat for many important food fishes. Caribbean coral reefs are also valued for a wide range of cultural and historical uses as well as their contributions to modern medicine.
Since the 1970s, however, some natural and man-made threats have lead to population declines of corals throughout the Caribbean including climate change, overfishing and harmful practices, and point and non-point sources of pollution. Coral reefs are further stressed by mass bleaching events, hurricanes, and diseases. As a result, many Caribbean reefs have undergone a coral-to-algae-dominated phase shift and no longer provide the ecological function that they once did. As these reefs erode, the economic, cultural, and medicinal values once provided will also be lost.
Throughout the Caribbean, Elkhorn and Staghorn corals were historically the most important reef builders. They are the fastest growing and their natural strategy of asexual fragmentation (where branches break, fall, and reattach to the seafloor) helped to create vast thickets.
The wide-scale decline of Caribbean Elkhorn and Staghorn corals has resulted in disconnected populations with low genetic diversity and poor mixing of genetic material during sexual reproduction. As a result, reef sites are now more vulnerable to population collapses. With some population levels lower than 10%, it is critical that pro-active interventions occur now if these corals are to survive the many impacts that threaten them today.
The Nature Conservancy has been involved in the conservation of Caribbean coral reefs since the 1990’s. Projects to reduce threats and larger efforts to conserve coral reefs and other marine life, through effectively managed Marine Protected Areas, have helped to improve the quality of coral reefs. In the case of these Caribbean Acroporid corals, however, those strategies alone will be slow to affect change.
In 2009, our team began our restoration efforts in the USVI using in-water coral nurseries to grow Elkhorn and Staghorn corals. The act of fragmenting one colony into many smaller colonies allowed us to create thousands of coral fragments in a short period of time. We were then able to transplant nursery-grown corals to carefully selected reefs that are considered relatively healthy, giving transplants the best opportunity to survive.
To date, 25,000 Elkhorn and Staghorn corals have been transplanted onto reefs around St. Croix and St. Thomas. We have observed our transplanted Staghorn corals grow into thickets and our Elkhorn corals mature into large adult colonies. Most recently, for the first time, our Elkhorn corals spawned (reproduce sexually) in a show that we will never forget.
Every year, after the full moon in August, Elkhorn corals spawn. Gamete bundles (carrying eggs and sperm) are released by the corals and float to the surface, where they break apart and mix with those from other colonies. Over the next few days, the fertilized eggs develop into free-swimming larvae and search for space on the sea floor to settle, attach, and build a new colony.
Observing our transplanted corals spawn has given us a renewed sense of hope for Caribbean coral reefs. As we continue to learn, expand, and share our work across the region and now across the world, we remain motivated by our results and our belief that, by working to protect nature, we are also working to preserve life.
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