What are coral reefs?
References
Coral Reef Alliance. “CORAL POLYPS — TINY BUILDERS.” Coral Reef Alliance, coral.org/coral-reefs-101/coral-reef-ecology/coral-polyps/.
NOAA. “Coral Reef Ecosystems.” Coral Reef Ecosystems | National Oceanic and Atmospheric Administration, www.noaa.gov/education/resource-collections/marine-life/coral-reef-ecosystems.
Ross, Rachel. “What Are Coral Reefs?” LiveScience, Purch, 24 Sept. 2018, www.livescience.com/40276-coral-reefs.html.