Coral diseases, particularly in the Caribbean, have caused major declines in coral populations, especially affecting staghorn (Acropora cervicornis) and Elkhorn (A. palmata) corals, which play a crucial role in reef ecosystems. Despite efforts to identify the pathogens that cause diseases like White Band Disease (WBD), and Stony Coral Tissue Loss Disease (SCTLD), the specific agents remain largely unknown. Coral restoration programs aim to restore these once abundant coral species, but the effectiveness is threatened by multiple stressors, including increases in disease frequency and nutrient pollution caused from runoff from land-based activities.
A recent study by scientists at the University of Miami NOAA Cooperative Institute for Marine and Atmospheric Studies (CIMAS), and the Atlantic Oceanographic and Meteorological Laboratory (AOML), which examined threatened Staghorn coral species (Acropora cervicornis), has uncovered important insights into how different coral genotypes respond to environmental stressors. The findings indicate that while some coral genotypes displayed resistance to either high nutrient levels or disease, none were resistant to both stressors simultaneously.
The scientists tested 10 genotypes commonly used in coral restoration in South Florida. Coral samples were collected from different offshore nurseries from (Coral Restoration Foundation, Florida Fish and Wildlife, and Rosenstiel’s Rescue a Reef Program) and transported to the NOAA CIMAS Experimental Reef Lab where they were exposed to two nutrient conditions: normal (ambient) or high ammonium levels for about 1.5 months. After this period, each coral was either exposed to a coral diseased tissue slurry or a healthy tissue slurry (i.e., placebo), creating four treatment groups: normal nutrients + placebo, normal nutrients + disease, high nutrients + placebo, and high nutrients + disease.
Key findings include:
• Coral genotypes that previously showed disease resistance did not necessarily maintain that resistance in this experiment, suggesting disease susceptibility may change based on disease cause, environment, or route of infection.
• Elevated dissolved inorganic nitrogen, in the form of ammonium, reduced coral survival—even in the absence of disease—highlighting poor water quality as a significant threat.
• When exposed to disease under normal conditions, four genotypes suffered complete mortality, while others showed varying degrees of resilience.
• When both stressors were combined, all genotypes experienced mortality rates ranging from 30 to 100 percent.
The researchers reinforce the urgent need for improving water quality by limiting runoff to support coral conservation efforts. Since coral disease outbreaks often coincide with pollution-related stress, reducing nutrient pollution is critical to enhancing coral resilience and increasing the success of restoration projects.
"If water quality issues are not addressed, it will be difficult for both wild and restored coral colonies in Florida to survive." said Ana Palacio, the lead author of the study and a research scientist at CIMAS. "Our findings highlight the importance of selecting coral genotypes that are resilient to local stressors and ensuring improved water conditions before restoration efforts."
Coral reefs provide essential ecosystem services, including coastal protection, marine biodiversity, and economic benefits to fisheries and tourism. This study underscores the importance of science-driven policymaking and conservation strategies to safeguard these vital ecosystems for the future.
The study titled: “Genotypes of Acropora cervicornis in Florida show resistance to either elevated nutrients or disease, but not both in combination” was published in the journal PLOS One on March 26, 2025. The authors include Ana M. Palacio-Castro1,2, *, Danielle Kroesche3-4, Ian Enochs2, Chris Kelble2, Ian Smith1,2, Andrew C. Baker3, Stephanie M. Rosales1,2
Funding for the study was provided to Ana M Palacio-Castro, through the National Academy of Sciences’ National Research Council (NRC) Postdoctoral Fellowship and the Coral Reef Conservation Program (Grant 31250)
1 Cooperative Institute for Marine and Atmospheric Studies, University of Miami, Miami, Florida, USA, 2 Atlantic Oceanographic and Meteorological Laboratory, NOAA, Miami, Florida, USA, 3 Department of Marine Biology and Ecology, University of Miami, Miami, Florida, USA,4 NOVA Southeastern University, Davie, Florida, USA
