Coral reefs in the Florida Keys, Hawaii, and Australia’s Great Barrier Reef are showing alarming signs of stress. Where bright, living structures once stretched across the seafloor, many now appear ghostly and drained of color.
The vivid greens, yellows, and blues of the corals have faded. What remains looks more like underwater ruins than living ecosystems. This phenomenon, known as coral bleaching, happens when climate-driven ocean warming disrupts the delicate relationship between coral and the algae that live inside them.
Though the organisms remain alive, bleaching makes them vulnerable – to disease, starvation, and eventually, death.
But recent research out of Michigan State University, in collaboration with Duke University and the Hawaii Institute of Marine Biology, has uncovered something hopeful: certain corals can pass their heat tolerance to their offspring. This finding could help protect reefs around the world.
Corals under climate stress
Coral reefs support nearly a quarter of all marine species. They also protect coastlines and help sustain millions of people globally.
Recently, researchers discovered that resistance to heat isn’t just a fluke of one generation – It can be inherited.
“The Coral Resilience Lab in Hawaii has developed amazing methods to breed and rear corals during natural summer spawning,” said study co-author Rob Quinn.
“This is a true scientific collaboration that can support coral breeding and reproduction to cultivate more resilient corals for the warming oceans of the future.”
The color behind the corals
In exchange for shelter and nutrients, the algae use photosynthesis to produce sugars that feed their host – providing up to 95 percent of the energy it needs. It’s a tight-knit relationship. But when water gets too warm, that partnership breaks down.
Bleached coral has kicked out its algae. It becomes pale. It loses its source of energy. And it starts to struggle.
“Corals are like the trees in an old-growth forest; they build the ecosystems we know as reefs on the energetic foundation between the animal and algae,” said study co-author Crawford Drury.
A lab-to-ocean collaboration
Michigan State University, far from any tropical reef, brings a unique set of tools to the table. Samples collected from spawning events in Hawaii are sent to MSU, where researchers use a method called metabolomics to study them.
This technique lets scientists see what’s happening inside a coral’s cells at a specific moment. The goal is to find the biochemical fingerprints linked to thermal tolerance.
The experts analyzed sperm, eggs, embryos, larvae, and algae. The results showed that heat resistance comes from both the coral and its algae – and that this resistance successfully passes from parent to offspring.
“HIMB and MSU have developed a really amazing partnership. I’m just happy they’ve let me be a part of it. I can’t wait to see what comes out of it next,” said Ty Roach, a visiting faculty at Duke University and lead author of the new study.
Coral eggs carry algae
Rice coral comes in many forms – some branch out like tiny fingers, others spread flat like layered shelves. But they all share a remarkable feature: little grain-like bumps that inspired the name, and a surprising ability to pass thermal tolerance to the next generation.
Unlike many coral species that acquire algae from surrounding seawater, rice coral packages its eggs with algae from the start.
This means that both the coral and its symbiotic algae begin their journey together from the very first moments of life. That early partnership offers a head start in facing warming oceans.
Studying heat in coral babies
Quinn and his team used MSU’s advanced instruments to examine the chemistry of each sample. They set out to investigate whether the molecules linked to heat resistance – such as specific lipids – appeared consistently across generations.
The researchers discovered that even embryos and larvae, the earliest life stages, showed chemical signatures tied to their parents’ heat resilience.
“Corals usually spawn based on the lunar cycle; for our experiment, this means late nights around the summer new moons and months of work rearing coral larvae and juveniles,” Drury said.
Heat traits passed during spawning
One of those long nights left a big impression on MSU graduate student Sarah VanDiepenbos.
“It was such a serene, beautiful experience. The timing is impeccable, as the process only lasts 20 to 30 minutes total,” she said.
The coral bundles slowly float upward, trying to find another gamete to combine with once they get to the surface. This release is gradual, so they can have a maximum chance of finding spawn from a different coral.
“To have this algae’s thermal tolerance remain through an entire generation and all the stages of coral development – that’s surprising, and promising for the future of coral reefs,” Quinn said.
“Coral lipid biochemistry is maintained through all stages of development during reproduction. These lipids come from both the host coral and its algal symbiont, indicating there is crosstalk between them to prepare the next generation to resist bleaching.”
Coral resilience in a changing climate
The results don’t just offer insight. They offer an opportunity for action. Understanding how thermal resistance is passed down gives scientists better tools for restoring reefs. It also gives them a clearer sense of which corals are worth breeding in a changing climate.
“Our metabolomics research at MSU could support reef restoration efforts at places like the Kāneʻohe Bay by identifying corals that are resistant to bleaching,” Quinn said.
The oceans are changing. But thanks to research like this, we might be ready for what comes next.
The full study was published in the journal Nature Communications.
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