May 20th, 2021, 6:00AM / BY Emily Leclerc Coral reef health is an important indicator of the ocean’s well-being. Scientists can study corals to learn more about how climate change is affecting the oceans. (Wise Hok Wai Lum, CC-BY-SA-4.0) Coral reefs house roughly a quarter of all known marine species, making them some of the most biodiverse ecosystems on the planet. But as their environments have become less friendly from climate change in recent decades, corals are struggling to stay healthy and support the life that relies on them. Now, thanks to an emerging technique called environmental DNA (eDNA), researchers at the Smithsonian’s National Museum of Natural History can support worldwide efforts to understand how corals and the communities that depend on them are responding to global ocean change. What they find could help scientists understand and anticipate the threats coral reefs face.