Coral Disease Represents Ecological Crisis Greater Than 1988 Yellowstone Fires

By Caroline Rogers, Ph.D., U.S. Geological Survey

This article appeared in National Parks Traveler in September 2021.

A disease that threatens an entire ecosystem lies below the surface of the sea – out of sight and out of mind.

The disease, which is rapidly killing corals in Virgin Islands National Park, is a crisis at least on the scale of the 1988 fires that roared across Yellowstone National Park and the continuing infestations of hemlocks and other old growth trees in Blue Ridge Parkway and Great Smoky Mountains and Shenandoah national parks.

But unlike the forest challenges, this malady is hidden where it can’t always be seen and it is killing corals, which are particularly slow growing; recovery, if it even occurs, can take a particularly long time.

In January, National Parks Traveler called attention to endangered and threatened parks and noted the emergence in 2014 of stony coral tissue loss disease (SCTLD) in Florida and its spread to the Caribbean where it was first observed in 2017.

This deadly disease is still killing over 20 species of corals. Stony coral tissue loss disease is now present in national parks in Florida and the Virgin Islands, including Biscayne National Park, Buck Island Reef National Monument, Salt River Bay National Historical Park and Ecological Preserve, Virgin Islands National Park, Virgin Islands Coral Reef National Monument, and found most recently, in May, in Dry Tortugas National Park.

In the past, most coral reefs have declined from a combination of injuries from hurricanes, excessive sediments and nutrients, high seawater temperatures, vessel groundings, and other factors leading to a decrease in living coral and an increase in algae.

Many corals in the national parks are still recovering from damage from powerful hurricanes in September 2017.  But SCTLD is particularly destructive because it is further reducing already low numbers of coral and has the potential to drive some coral species, including Pillar Coral (Dendrogyra cylindrus), to extirpation.

Corals are architects of the reefs, just as large trees create forest structure. They are solar-powered animals that create a complex physical framework, a rocky structure. In a symbiotic relationship between the corals and the microscopic algae in their tissues, the coral animal receives nutrition from the algae (zooxanthellae), and the algae photosynthesize within the protection of the coral tissues, using carbon dioxide and nutrients from the coral animal. This symbiosis is the basis of all coral reefs as it results in the secretion of limestone rock (calcium carbonate) in a process called calcification.

Coral reefs are not only beautiful, a reason in itself to do all we can to protect them, but also economically valuable. They protect shorelines, including white sand beaches, from erosion during storms and support tourism based on snorkeling and diving. Fish and other reef animals are important as food. And we are just beginning to learn about the numerous drugs that can be derived from reef animals to combat cancer and other diseases.

Sadly, there has been a failure to acknowledge the contributions that reefs make to the well-being of the planet, and reefs around the world have deteriorated, particularly in the last 30 years, from natural and human-related stresses. Warming sea water temperatures that lead to coral bleaching with loss of the zooxanthellae is of the greatest concern. Disease outbreaks, sometimes but not always following coral bleaching, are responsible for the largest declines in coral on western Atlantic and Caribbean reefs.