Coral disease represents an ecological crisis comparable to the 1988 Yellowstone fires
Coral disease represents an ecological crisis greater than the 1988 Yellowstone fires
By Caroline Rogers, Ph.D., US Geological Survey
A disease that threatens an entire ecosystem lies beneath 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 at the scale of the 1988 fires that roared in Yellowstone National Park and continued infestations of hemlock and other ancient trees at Blue Ridge Parkway and Great Smoky Mountains and Shenandoah National Parks.
But unlike forest challenges, this disease is hidden where it cannot always be seen and it kills corals, which grow particularly slowly; recovery, if it even occurs, can take a particularly long time.
In January, National parks traveler drew attention to endangered and threatened parks and noted the emergence in 2014 of hard coral tissue loss disease (SCTLD) in Florida and its spread to the Caribbean where it was first observed times in 2017.
This deadly disease still kills more than 20 species of coral. The 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 Historic Park and Ecological Preserve , Virgin Islands National Park, Virgin Islands Coral Reef National Monument, and most recently found in May in Dry Tortugas National Park.
In the past, most coral reefs have shrunk due to a combination of hurricane injury, excessive sediment and nutrients, high seawater temperatures, shipwrecks and d ‘other factors leading to a decrease in living coral and an increase in algae.
Many corals in national parks are still recovering from the damage caused by the powerful hurricanes of September 2017. But the SCTLD is particularly destructive as it further reduces an already low number of corals and has the potential to hunt certain species of corals, notably Pillar Coral (Dendrogyra cylindrus), on extirpation.
Corals are the architects of reefs, just as tall trees create the structure of the forest. They are solar powered animals that create a complex physical frame, a rock structure. In a symbiotic relationship between corals and the microscopic algae in their tissues, the coral animal feeds on algae (zooxanthellae) and the algae photosynthesize as part of the protection of coral tissue, using carbon dioxide and nutrients of the coral animal. This symbiosis is the basis of all coral reefs because it results in the secretion of limestone (calcium carbonate) in a process called calcification.
Coral reefs are not only beautiful, which is in itself a reason to do everything in our power to protect them, but they also have economic value. 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 discover the many drugs that can be derived from reef animals to fight cancer and other diseases.
Unfortunately, there has been no recognition of the contribution of reefs to the well-being of the planet, and reefs around the world have deteriorated, especially over the past 30 years, due to natural and human stresses. . Of most concern is the warming of the seawater temperature which results in coral bleaching with the loss of zooxanthellae. Epidemics, sometimes but not always after coral bleaching, are responsible for the greatest coral declines on reefs in the West Atlantic and Caribbean.
Here’s a closer look at the effects of the disease in Virgin Islands National Park after it emerged in early 2020, and a look at recent research efforts to learn more about it.
What does it look like?
When portions of corals die from SCTLD and other diseases, their white limestone skeleton is revealed. The crisp white corals are clearly visible and easily seen for anyone snorkeling in the Virgin Islands National Park. Maho Bay and Trunk Bay, the two most popular snorkeling spots in the park, are currently home to highly visible diseased corals in shallow water. Most of the corals near Waterlemon Cay, another very popular site, are dead, including the pillar corals towering over 6 feet.
What is happening?
Scientists believe that SCTLD strikes at the base of all coral reefs — the symbiotic relationship between coral animals and algae (zooxanthellae) inside their tissues. This relationship results in calcification which results in the physical structure of the reef. Scientists from the US Geological Survey and other agencies have found microscopic lesions in diseased corals in Florida that indicate a possible disruption of this fundamental relationship.
More Recent Coral Investigations with SCTLD by Dr Thierry Work with the USGS National Wildlife Health Center-Honolulu Field Station using electron microscopy revealed abnormalities in zooxanthellae associated with viral particles, suggesting that SCTLD could be caused by a virus that kills zooxanthellae, resulting in the death of coral host cells and subsequent tissue loss. Further work is underway to try to confirm this.
In July, Dr Work collaborated with National Park Service scientists Jeff Miller and Thomas Kelley to collect samples of diseased and apparently healthy corals in the Virgin Islands National Park to determine if corals affected by SCTLD displayed the same lesions. at the coarsely visible and microscopic level. like in Florida. Corals from 13 species were sampled for examination by microscopy and molecular biology for virus identification. Some samples have been taken from corals present at long-term monitoring sites maintained by the NPS and USGS for the past 30 years, a period in which the park has developed a history of coral disease.
The NPS South Florida and Caribbean Network’s inventory and monitoring program has documented a decline in coral cover at its sites over the long term. Corals covered about 25 percent of the monitored areas 25 years ago, have fallen to about 12 percent in 2007, and now scientists are predicting a decline to less than 5 percent due to SCTLD. The disease is now widespread among star corals (Orbicelle sp.) which account for most of the remaining coral cover on the reefs.
The only direct response attempted to date is the treatment of already diseased corals with an antibiotic paste which is not 100% effective. Frank Cummings, director of the nonprofit Caribbean Oceanic Restoration and Education Foundation, leads treatment efforts in the U.S. Virgin Islands with staff from the University of the Virgin Islands and scientists from the Mote Marine Laboratory.
Many marine national parks have been designated, at least in part, to protect and conserve the precious coral reefs found there. Resources are limited to respond to this new crisis affecting coral reefs. While the waters of the Virgin Islands National Park are still clear and beautiful, and the beaches attract more visitors than ever before, the significant loss of corals could have adverse effects on the entire marine ecosystem, including the colorful fish, octopus and sea. turtles.
Caroline rogers is a Marine Ecologist at the Wetland and Aquatic Research Center based at USGS Caribbean Field Station in St. John, US Virgin Islands. Previously, she was a research biologist at the National Park Service in the Virgin Islands National Park (1984 – 1993). She has over 30 years of experience in coral reef research and has published articles on coral diseases, effects of sedimentation, effects of hurricanes, damage from boat anchors, surveillance at long term, reef productivity, recruitment of corals and endangered coral species. Acropora palmata.