To enhance the survival of rare elkhorn corals in Florida’s waters, 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 suggest placing these corals in shallow areas with strong currents. This recommendation comes from their study titled “Reef site and habitat influence effectiveness of Acropora palmata restoration and its microbiome in the Florida Keys” published on November 11, 2024, in Communications Earth & Environment.
This research provides essential insights for coral restoration initiatives, as elkhorn coral is a vital reef-building species in Florida and the Caribbean. Their intricate, branch-like structure is crucial for supporting reef ecosystems and providing habitats for various marine species.
A NOAA assessment released in 2024 revealed that the Florida Coral Reef experienced a 75% loss of its restored elkhorn coral populations during the marine heat wave in the summer of 2023. The decline of elkhorn corals negatively impacts the overall health of the ecosystem, often leading to the encroachment of other species like sponges, macroalgae, and non-reef-building organisms.
One significant conclusion from the study is that outplanting elkhorn coral colonies should focus on shallower depths with faster currents in low-nutrient settings to foster a healthier microbial community.
Additional key findings include:
- Variations in environmental conditions across different reef habitats are linked to differences in coral survivorship. Specifically, higher survivorship is associated with increased current velocity and shallower depths.
- Certain bacteria are linked to the survival of corals.
- Increased levels of nitrate, nitrite, and temperature, especially during the summer, can harm elkhorn corals at the microbial level, potentially leading to a decline in beneficial bacteria and an increase in harmful pathogens.
“Understanding how coral genetics and the surrounding environment affect restoration success can help guide conservation efforts worldwide,” said 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 the survival rates of four genets across three actively restored reefs in the upper Florida Keys. (Genets refer to a genetically unique colony or a group of colonies originating from a single reproductive event.)
The scientists gathered various habitat data, including measurements of dissolved inorganic nutrient levels, ocean current patterns, satellite-derived sea surface temperatures, and chlorophyll-a concentrations obtained from ocean color assessments, along with coral outplant survival rates and microbiome information. They analyzed these data sets to explore the interactions among these factors.
Coral reefs are vital ecosystems that support a rich diversity of life, providing habitats for approximately 25% of all marine species. They also play a crucial role in protecting coastlines from erosion, supporting fisheries, and boosting tourism economies. Unfortunately, these reefs face significant threats from rising ocean temperatures, acidification, pollution, and overfishing.
The effectiveness of coral restoration projects, such as the outplanting of elkhorn coral, can help counteract reef degradation and safeguard these essential ecosystems. By understanding the impact of genet survivorship, environmental conditions, and the coral microbiome on restoration success, coral managers can make better-informed decisions about the most effective strategies for reef restoration.
“Local governments, environmental groups, and coastal managers can apply this knowledge to make better decisions about where to focus restoration projects and how to care for existing coral populations, ultimately helping with fisheries and coastline protections,” said Rosales.
“It is important to highlight that this study was conducted during a year of minimal bleaching in the Florida Keys. Understanding how bacteria, along with environmental factors such as currents and depth, interact during periods of severe temperature stress and influence coral survivorship remains a critical area for further investigation,” added Rosales.
