Elkhorn CoralThe National Oceanic and Atmospheric Administration (NOAA) Fisheries Service announced in November a proposal to list 66 coral species, such as the elkhorn coral (Acropora palmata) pictured above, as either endangered or threatened under the Endangered Species Act of 1973 (ESA). Fifty-nine of the coral species are found in the Pacific while seven are found in the Caribbean.

Climate change and ocean acidification are the leading threats to coral species, according to a biological review team convened by NOAA to assess the status of coral species in U.S. waters.

Elkhorn coral is already listed as threatened under the ESA. But disease, bleaching events—when corals lose the symbiotic algae that gives them their color—and low genetic diversity are pushing this species into further declines, prompting the proposal to bump its status to endangered. (See related photos of corals.)

Photograph by Luis Javier Sandoval, Oxford Scientific/Getty Images