Corals are essential to biodiversity in the ocean. They provide food and shelter for a a variety of fish species, serving as a biological anchor for vast marine ecosystems. But corals are under threat. They're on the decline throughout the world thanks to ocean acidification, rising ocean temperatures, and growing pollution.

It was largely these trends and environmental factors that inspired the National Oceanic and Atmospheric Administration (NOAA), on Tuesday, to announce the protection of 20 new coral species. The agency's ruling means there are now 10 times as many coral species on the Endangered Species List than there were previously. Prior to Tuesday's ruling, only the Caribbean's elkhorn and staghorn corals had been offered federal protection.

Because the 20 new corals are currently only listed as "threatened" and not "endangered," the new ruling won't necessarily place any additional restrictions on activities in, around or involving the corals. But it will empower federal regulators to keep a closer watch on how human activities and development affect these vulnerable marine organisms. The NOAA -- in conjunction with other federal and local conservation agencies -- could institute more stringent restrictions in the future.

"We will continue to work with communities to help them understand how the agency's decision may or may not affect them," the NOAA said in a press release. "The tools available under the Endangered Species Act are sufficiently flexible so that they can be used in partnership with coastal jurisdictions, in a manner that will allow activity to move forward in a way that does not jeopardize listed coral."

"We will now work with partners on mitigation measures and recovery strategies for the newly listed corals, building from approaches that have shown success elsewhere," the agency added.

"Most of these species, particularly in the Caribbean, have started to experience some impacts from bleaching and elevated temperatures and disease," David Bernhart, a biologist with NOAA Fisheries Service in St. Petersburg, Fla., told National Geographic. Bleaching is when coral expel the symbiotic algae living inside them -- usually in reaction to rising water temperature. When corals bleach themselves, they are not dead, but they are momentarily much more vulnerable to other environmental stressors.

Bernhart hopes the new ruling will instigate more proactive conservation and recovery programs -- and help keep the corals from ever having to have their designation switched from "threatened" to "endangered."