Coral diseases and water quality play a key role for coral restoration and survival efforts
Coral restoration programs are expanding to revive coral populations and ecosystem services, but local and global stressors such as coral disease and water pollution still threaten coral survival
University of Miami Rosenstiel School of Marine, Atmospheric, and Earth Science
image:
A healthy staghorn coral fragment donated by the coral nurseries – representative of a healthy coral fragment
view moreCredit: Diana Udel, University of Miami
Coral restoration programs are expanding to revive coral populations and ecosystem services, but local and global stressors such as coral disease and water pollution still threaten coral survival.
Miami, FL – 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 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
Stephanie Rosales (left) and Ana Palacio (right) evaluating staghorn coral genotypes during their exposure to elevated nutrients
Diseased corals collected to use for disease slurry
An experimental fragment that developed a disease lesion after exposure to disease slurry
Credit
Stephanie Rosales, University of Miami
Stephanie Rosales (left) and Ana Palacio, lead author of the study (right), evaluating diseased corals
Tissue samples collected from a fragment that developed disease signs
Credit
Diana Udel, University of Miami
Journal
PLOS One
Method of Research
Experimental study
Subject of Research
Not applicable
Article Title
Genotypes of Acropora cervicornis in Florida show resistance to either elevated nutrients or disease, but not both in combination
Article Publication Date
26-Mar-2025
By AFP
March 26, 2025
A months-long marine heatwave had "cooked" the sprawling Ningaloo Reef, according to scientists - Copyright Minderoo Foundation/AFP Violeta J Brosig
Steven TRASK
An “unprecedented” mass bleaching event has been recorded off Australia’s western coast, scientists said Wednesday, turning huge chunks of a celebrated reef system a sickly dull white.
A months-long marine heatwave had “cooked” the sprawling Ningaloo Reef, ocean scientist Kate Quigley said, part of a world heritage-listed marine park renowned for vibrant corals and migrating whale sharks.
Although environment officials were still verifying the scale of damage, data collected by Quigley and a team of scientists found it was on track to be the reef’s worst mass-bleaching event in years.
“Warm oceans have just cooked the corals this year,” Quigley told AFP.
“It wouldn’t be amiss to throw in the word ‘unprecedented’.
“It has gone deep, it’s not just the top of the reef that is bleaching. Many different species of coral are bleaching.”
Branching through shallow waters along Australia’s western coast, the 300-kilometre (185-mile) Ningaloo Reef is one of the largest “fringing reefs” in the world.
The unfolding mass bleaching looked to be the worst since 2011, Quigley said.
Ocean waters lapping Western Australia have been as much as three degrees warmer than average over recent summer months, the government weather bureau said.
Rising temperatures shot past the “bleaching threshold” sometime in mid-January, according to monitoring by the US National Oceanic and Atmospheric Administration.
Bleaching occurs when warm waters trigger a biological response forcing coral to expel the colourful algae embedded in their tissues.
“Bleaching is a sickness, but it does not mean outright death,” said Quigley, a research scientist with environment-focused charity Minderoo Foundation.
“But if it is bad enough, the corals will die.”
– ‘Just shocking’ –
Government data showed smaller patches of coral bleaching had also been spotted at the northern tip of the more famous Great Barrier Reef on Australia’s east coast.
Quigley said the Ningaloo Reef and the Great Barrier Reef were shaped by different weather patterns — and it was rare to see bleaching on both at the same time.
“What we’re seeing is the level of ocean warming is so great, it’s overriding the local conditions in some places.
“It’s just shocking. When we take a national snapshot, it’s extremely concerning.”
The Great Barrier Reef, a popular tourist drawcard, has suffered five mass bleachings over the past eight years.
Quigley said the extent of damage on the Great Barrier Reef was not currently widespread enough to be considered “mass bleaching”.
Global average temperatures were the hottest on record in 2024, with prolonged heatwaves in many of the planet’s oceans causing alarm.
A prolonged global episode of heat-related bleaching impacted almost 80 percent of the world’s coral reefs between 2023 and 2024, a leading US science agency found in October.
Warming seas, overfishing and pollution are threatening coral reef systems the world over, warned a major UN report in December.
The average sea surface temperature around Australia was the “highest on record” in 2024, an Australian National University study reported last week.
Australia sits on bulging deposits of coal, gas, metals and minerals, with mining and fossil fuels stoking decades of near-unbroken economic growth.
But it is increasingly suffering from more intense heatwaves, bushfires and drought, which scientists have linked to climate change.
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