To assist rare elkhorn corals in thriving within Florida’s waters, experts recommend placing them in shallow ocean areas with strong currents, as highlighted by researchers from the University of Miami NOAA Cooperative Institute for Marine and Atmospheric Studies and the University of Miami Rosenstiel School of Marine, Atmospheric, and Earth Science in a recent study.
This new information is crucial for coral restoration efforts because elkhorn coral colonies play an essential role as a reef-building species in Florida and the Caribbean. Their intricate branch-like structure provides vital support for reefs and serves as a habitat for numerous reef species.
A NOAA report from 2024 revealed that the Florida Coral Reef suffered a 75% decline in its restored elkhorn coral populations during the marine heat wave in summer 2023. This decline negatively impacts the overall health of the ecosystem and often leads to the emergence of other species, like sponges and macroalgae, which do not contribute to reef building.
One major finding of this study is that outplanting elkhorn coral colonies should focus on shallower depths with rapid currents in environments low in nutrients to foster a healthier microbial community.
Additional findings include:
- Subtle variations in environmental conditions across reef habitats relate to differences in coral survivorship. Specifically, higher elkhorn survivorship is linked to factors like faster current speeds and shallower reef depths.
- Certain types of bacteria are associated with better survival rates in corals.
- Higher concentrations of nitrate, nitrite, and temperatures—especially in the summer—harm elkhorn corals at the microbial level, potentially reducing beneficial bacteria and increasing harmful pathogens.
“Comprehending how coral genetics and their environment influence restoration success can guide global conservation initiatives,” stated Stephanie Rosales, the lead author of the study and an associate scientist at the Rosenstiel School’s Cooperative Institute for Marine and Atmospheric Studies.
In 2019, the research team tracked survivorship rates of four genetically distinct groups, known as genets, across three coral reefs in the upper Florida Keys that are part of ongoing restoration efforts. (Genets are unique coral colonies that trace back to a single reproductive event.) The scientists gathered various habitat data, assessing nutrient concentrations, ocean current dynamics, satellite sea surface temperatures, and chlorophyll-a levels. They also collected information on coral outplant survivorship and microbiome data, establishing correlations to understand the interplay of these factors.
Coral reefs are vital ecosystems supporting biodiversity and habitat for about 25% of all marine species. They shield coastlines from erosion, bolster fisheries, and enhance tourism economies. Nevertheless, these reefs face significant threats from rising ocean temperatures, acidification, pollution, and overfishing.
The success of restoration initiatives, such as replanting elkhorn coral, can play a key role in counteracting reef degradation and preserving these ecosystems. Recognizing the importance of genet survivorship, environmental factors, and the coral microbiome enables coral managers to effectively strategize restoration efforts.
“By leveraging this insight, local governments, environmental organizations, and coastal managers can make more informed decisions regarding the focus of restoration initiatives and the care of existing coral communities, ultimately aiding fisheries and coastal protection,” Rosales noted.
“It’s crucial to point out that this study was conducted during a year with minimal coral bleaching in the Florida Keys. Further investigation is needed to understand how bacteria, combined with environmental stressors like currents and depth, affect coral survival during extreme temperature conditions,” Rosales added.
The research, titled “Reef site and habitat influence effectiveness of Acropora palmata restoration and its microbiome in the Florida Keys,” was published on November 11, 2024, in the journal Nature Earth & Environment.
The research team features Stephanie M. Rosales, Benjamin D. Young, Allan J. Bright, Enrique Montes from the University of Miami Cooperative Institute for Marine and Atmospheric Studies, the Atlantic Oceanographic and Meteorological Laboratory, NOAA, Jia-Zhong Zhang from the same lab, Nikki Traylor-Knowles of the Rosenstiel School, and Dana E. Williams from the Southeast Fisheries Science Center of NOAA.
Funding for the study came from NOAA’s ‘Omics OAR grant # NO_0019 and NOAA’s Coral Reef Conservation Program.
