A few days after a full moon on a sultry summer evening, a light current and sea water temperature of about 85 degrees created the perfect conditions for coral sex in the Florida Keys.
Orbicella vaveolata, or mountainous star corals, were getting it on at Horseshoe Reef and Elbow Reef off Key Largo, releasing their reproductive cells in the water during an annual spawning event that lasted only a couple of days.
“The corals released the eggs and sperm in little bundles that look like Dippin’ Dots ice cream,” said Liv Williamson, a coral researcher at the University of Miami Rosenstiel School of Marine and Atmospheric Science. She was in Key Largo in August and witnessed the incredible act of synchronicity when all corals in the area ejected millions of little pink balls that floated up to the surface of the water, fertilized and turned into larvae. “It looks like you’re in a snow globe underwater and it’s really, really spectacular to see,” she said. Like most species of coral, the mountainous star is a hermaphrodite: It releases both eggs and sperm when it reproduces.
Williamson, who doesn’t mind being called “coral mama” for her work, scooped up some tiny larvae from the ocean, put them in a bottle filled with seawater and drove back to the Coral Reef Futures Lab at the Rosenstiel School campus on Virginia Key. Her mission: to “vaccinate” the larvae against climate change and hopefully save them from annihilation. The research is part of an ambitious UM-led coral restoration project that just got a $6 million boost from the federal and state governments.
At the lab, under precisely controlled light and water conditions, the babies will be stress-hardened: exposed to heat levels that could almost kill them, in hopes that they might be able to withstand climate change and all its devastating consequences. The goal is for the juveniles to become a new generation of stronger corals that can breathe new life into Florida’s reefs before they are gone forever, which could lead to a collapse in fish populations and marine life.
Williamson and her colleagues at Rosenstiel believe the secret to making corals more resilient to climate change is in the algae that live inside them. They have a mutually beneficial relationship that gives reefs their colors, provides algae with shelter and supplies both organisms with the energy they need to live. If baby corals take up algae species that have a higher tolerance to heat, they will have better chances of survival once they are transplanted back to a warming ocean. She is also working with adult corals, encouraging them to partner with more resilient algae and testing the success of this strategy in the wild.
Breeding corals in labs and stressing them with different heat and light conditions aren’t new techniques in conservation research but efforts to boost coral health have taken on a sense of urgency as threats to reefs around the world intensify. More frequent bleaching events – when corals are hurt by changes in conditions as temperature, light or pollution, and expel their symbiotic algae, causing them to go completely white – and disease outbreaks have decimated reefs.
In the past three decades more than 25% of the world’s coral cover has been lost. The most recent bleaching in 2016 wiped out a third of shallow-water corals in the Great Barrier Reef.
In Florida, more than half of the corals have disappeared over the past 250 years, hammered by development, pollution, boat anchors, frequent bleachings and, recently, a mysterious disease that’s ravaging colony after colony of the only inshore reef tract in the continental United States.
The health of Florida’s coral reefs is crucial for the state. They create habitats that provide shelter and food for hundreds of species, from fish to lobster. The reef also serves as a buffer that protects coastal areas against hurricanes and storm surge. The U.S. Geological Survey estimates that reefs protect more than $675 million worth of coastal infrastructure in Florida. Earlier this year the National Oceanic and Atmospheric Administration said coral reefs in southeast Florida have an asset value of $8.5 billion and generate $4.4 billion in local sales, $2 billion in local income and 70,400 full- and part-time jobs.
Wildlife managers are taking note, and more funding is being granted to restoration. Researchers at the University of Miami last week were awarded $6 million to establish the Southeast Florida Coral Reef Restoration Hub, a research project focused on restoring coral reefs in Miami-Dade and Broward counties. The National Fish and Wildlife Foundation and National Coastal Resilience Fund provided the initial $3 million grant, which was matched by donors including local and federal governments, companies and the University of Miami’s Laboratory of Integrative Knowledge.
The team led by UM Rosenstiel School professors Diego Lirman and Andrew Baker will restore 125 acres of reef habitat by planting over 150,000 coral colonies and larvae from five species.
In addition to increasing the abundance of colonies in South Florida, the project aims to create diversity and build climate resistance into the new coral, Baker said.
“We will be doing pretty aggressive restoration involving not just planting corals that we grow in nurseries, but also planting out tens of thousands of coral recruits onto the reefs to inject more genetic diversity,” he said. Recruits are the coral juveniles that Williamson is working on making stronger at the UM lab, with the help of more heat-tolerant algae.
Simulating the sea
After swimming around for a few days in tanks the size of a large utility sink, the larvae that Williamson collected in Key Largo settled on small pucks placed on the bottom and started growing skeletons, mouths and tentacles. A maze of PVC pipes and electrical wires crisscross the lab, and the constant hiss of filtered saltwater squirting through faucets and tubes dominates the place. Different current and water temperature conditions are simulated in the tanks, and the lights are hooked to an app so that they mimic what the corals would experience if they were 30 feet underwater.
Next to the juveniles, fragments of adult elkhorn and staghorn corals, species that used to dominate the Florida reef tract and have been severely affected by bleaching events, are being exposed to a sub-lethal level of ocean warming. Once they expel their algae and bleach, scientist lower the temperature and introduce the hardier algae, allowing the corals to recover and become stronger.
For a couple of years now, the stress-hardened corals are being used to repopulate reefs in Biscayne Bay, with the help of citizen scientists and corporate sponsors, as part of the Rescue a Reef program.
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