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Threatened Tropical Coral Reefs Form Complex, Ancient Associations with Bacteria, Researchers Say

By November 29, 2018No Comments

When it comes to the well-being of coral reefs, for many years scientists focused on bleaching, an event that can endanger corals and the diverse marine ecosystems that they support. In bleaching, high temperatures or other stressors cause corals to expel Symbiodinium, the beneficial, brightly colored microbes that would normally share excess energy and nutrients with corals. Bleaching ultimately starves corals and endangers the entire reef ecosystem.

But over the last two decades, scientists have realized that other microbes are also critical for coral health, including communities of bacteria that live on coral surfaces and in their tissues. These bacteria constitute the coral microbiome. High temperatures — even below the threshold for bleaching — can disrupt coral microbiomes, leaving corals vulnerable to disease.

But scientists lack comprehensive data about the bacteria that make up the microbiomes of the more than 1,500 coral species worldwide. That is starting to change thanks to the Global Coral Microbiome Project, a collaboration among researchers at the University of Washington Bothell, Pennsylvania State University and Oregon State University. The team is studying the diversity of bacteria within corals and how it has changed over time.

In their first comprehensive survey of healthy corals, published Nov. 22 in the journal Nature Communications, the team reports that coral bacteria are a surprisingly diverse bunch — and that different sections of the coral body can host unique communities of bacteria.

“This project represents one of the most comprehensive efforts to identify what kinds of bacteria are present in diverse groups of tropical corals, how the types of bacteria can differ over coral anatomy, and how the symbiotic relationships between corals and bacteria have changed over coral evolution,” said senior and corresponding author Jesse Zaneveld, an assistant professor of biological sciences at UW Bothell.