Mission: Iconic Reefs measures how many coral larvae want to settle in the Florida Keys
By Scott Atwell
Dr. Jenny Mallon inserts a calcification accretion unit on the seafloor under permit from Florida Keys National Marine Sanctuary. Photo: Shane Gallimore/NOAA; Three-month old coral recruits of the species Diploria labyrinthiformis (common name: grooved brain coral) labeled to illustrate the number of millimeter-sized recruits. NOAA.
If coral larvae responded to advertising, Dr. Mark Ladd’s pitch could go something like this:
Pssst. I see you drifting by looking for a place to settle, and boy, do I have a deal for you! It’s a modern one bedroom with a couple of PVC tiles that look just like those hard, rock-like surfaces you favor in the wild, and some shaded over-hangings to protect you from things that want to eat you. It’s a great place to start a colony of your own. You know, build out the whole suburban lifestyle. We have a five-star guest rating online so, what do you say?
Ladd’s B&B is part of a research project for Mission: Iconic Reefs, a large-scale NOAA-led and partner-driven coral restoration initiative in NOAA’s Florida Keys National Marine Sanctuary. The dwelling structures, called calcification accretion units (CAUs), mimic the places larvae settle naturally before growing calcium carbonate structures that become coral reefs. CAUs are left on the seafloor for up to a year, and then retrieved for scientists like Ladd to record the number of coral recruits and the weight of calcified material that accumulated on the tiles.
“We are interested in coral recruitment because this is a fundamental process for the persistence of coral populations on reefs,” said Ladd, a coral research scientist and lead of the Coral Ecology Unit at NOAA’s Southeast Fisheries Science Center in Miami.
Mission: Iconic Reefs is only five years into its 20-year plan to outplant five million corals on seven important reefs in waters many call the fishing and diving capitals of the world. Coral reefs are the foundation for the state’s recreation and tourism industry, which generates over $2 billion and 20,000 jobs annually in the Florida Keys.
Ladd is interested in understanding how these restoration efforts impact coral populations’ ability to be self-sustaining through sexual reproduction. The recent deployment of more than 30 CAUs at Horseshoe Reef and Cheeca Rocks will establish a baseline—a “before” snapshot—for comparison with future measurements taken after outplanted corals mature and spawn on their own.
“This will allow us to measure if and how restoration efforts influence coral recruitment in the future,” Ladd explained. “The experimental design for the tile deployments lets us assess coral recruitment across Mission: Iconic Reefs sites as a whole; across different habitats, like forereef terrace vs. patch reefs; and among reef sites. We are also deploying tiles in control and restored plots at Mission: Iconic Reefs sites, thus allowing us to test if restoration has an effect on coral recruitment at smaller scales.”
Ladd and Dr. Jenny Mallon, a post-doctoral research fellow from Nova Southeastern University, teamed up with Mission: Iconic Reefs field team members to deploy the tiles inside sanctuary waters in the Florida Keys.
“We are looking for relatively clear spaces, free of larger types of algae and soft corals that could physically interfere with the recruitment process on these tiles,” said Shane Gallimore, a marine stewardship and monitoring specialist who took part in the work. Across all seven Mission: Iconic Reef sites, 252 tile units will be established across 63 plots.
“This type of research is important because it helps us quantify coral recruitment and determine what, if any, bottlenecks exist in the process,” said Dr. Katey Lesneski, research and monitoring coordinator for Mission: Iconic Reefs. “For example, if there are low rates of reproduction, there would be little to no recruits found in these tiles. If there is adequate reproduction and we find recruits on the tiles but not on nearby reef structure, either the natural reef structure is not suitable habitat, or another cause of early mortality, like predation, is present. From there, we can consider interventions such as increasing the density of reproductive-sized colonies, or improving the amount of suitable habitat especially around the spawning season.”
The health of coral reefs is a leading indicator for the economic outlook of fishing, diving, and other marine recreational activities. NOAA is investing in Mission: Iconic Reefs through several programs, including its National Marine Fisheries Service, Coral Reef Conservation Program and the Office of National Marine Sanctuaries.