The Florida Reef Tract is the third-largest barrier reef ecosystem in the world and is home to a rich assortment of over 6000 marine species, including a wide variety of over 65 species of stony corals. The high level of biodiversity associated with the reef makes it one of the most productive marine ecosystems, and many people depend on them for food and other resources, while others simply enjoy recreational activities that they offer, such as boating, fishing, snorkeling, and SCUBA diving. In Florida, particularly, the reefs are a significant contributor to the economy, generating an estimated $6.3 billion per year, as they attract more than 30 million visitors annually.
However, coral reefs are becoming increasingly endangered and face a number of threats, including climate change, pollution and increasing prevalence of diseases. The stability and health of the Florida Reef Tract is of particular concern, as the system is experiencing significant losses in coral species and associated organisms. One of the major contributors to coral die-off is diseases, especially tissue loss diseases, such as the black-band disease, white-band disease, acropoid serratiosis, dark spot syndrome and white plague. One of the most recently identified and damaging diseases to infect the Caribbean waters is the stony coral tissue loss disease (SCTLD), which affects over half of Florida’s coral reef ecosystem.
Stony Coral Tissue Loss Disease:
SCTLD is a deadly disease found in over 20 scleractinian coral species in the Caribbean. It was first identified in corals inhabiting the Virginia Key, off the coast of Florida, in late 2014. Since then, the disease has spread throughout the wider Caribbean Region, affecting reefs along the coastlines of Mexico, Jamaica, the U.S. and the British Virgin Islands, Sint Maarten, the Turks and Caicos Islands, the Dominican Republic, Belize, Sint Eustatius, Puerto Rico, the Bahamas, the Cayman Islands, Honduras, and most recently it has been detected in St Lucia and Guadeloupe.
The multi-year outbreak of this tissue loss disease has caused significant damage to some of the slowest-growing and longest-lived corals within the Florida Reef Tract and other infected reefs. Although diseases are fairly common in reefs, usually affecting around 1-2% of corals, this disease is particularly concerning due to its rapid progression, extended duration, unusually high mortality rates, the high number of species susceptible to infection and the large geographic range over which it has spread. Although the transmission agent has not been confirmed, it is thought to be transmitted through bacterial pathogens, either through direct contact or through water movement.
How You Can Help:
It is vital to track the spread of the disease, and if you are a keen SCUBA diver or snorkeler and you observe the disease infecting corals at previously unknown locations, take a photo of the infected coral and note the dive site, coral location and date, and report your sighting to the Atlantic and Gulf Rapid Reef Assessment website.
How To Identify SCTLD:
SCTLD can easily be confused with other diseases, coral bleaching or fish bites. In order to distinguish SCTLD from these, it is important to note which types of corals are affected and the pattern of the spread of the damaged tissue.
Susceptibility to SCTLD varies among coral species, but the most affected taxa within the reef ecosystem are the pillar, star and brain corals. Soft and branching corals are not susceptible to this disease. Staghorn corals and elkhorn corals, for instance, which are critically endangered, appear to be immune to the disease.
Affected species include:
· Lettuce coral (Agaricia agaricites)
· Fragile saucer coral (Agaricia fragilis)
· Boulder brain coral (Colpophyllia natans)
· Elliptical star coral (Dichocoenia stokesii)
· Grooved brain coral (Diploria labyrinthiformis)
· Smooth flower coral (Eusmilia fastigiata)
· Maze coral (Meandrina meandrites)
· Great star coral (Montastraea cavernosa)
· Ten-ray star coral (Madracis auretenra)
· Mustard hill coral (Porites astreoides)
· Clubtip Finger Coral (Porites porites)
· Symmetrical brain coral (Pseudodiploria strigosa)
· Knobby brain coral (Pseudodiploria clivosa)
· Lesser starlet coral (Siderastrea radians)
· Massive starlet coral (Siderastrea siderea)
· Smooth star coral (Solenastrea bournoni)
· Blushing star coral (Stephanocoenia intersepta)
In addition, the following endangered species are also susceptible:
· Pillar coral (Dendrogyra cylindrus)
· Cactus coral (Mycetophyllia spp.)
· Lobed star coral (Orbicella annularis)
· Mountainous star coral (Orbicella faveolata)
· Boulder star coral (Orbicella franksi)
Infected corals are characterized by a distinctive lesion of dead tissue that typically starts from the base of the coral and spreads over the entire colony, leaving behind just the hard white exoskeleton. The lesions may also first appear as an irregular series of blotches that coalesce over time and impact the entire colony. The survival of coral also varies, but small colonies typically die over a number of weeks or months, whereas larger colonies may survive over a number of years.
Loss Of Iconic Mountainous Star Coral, “Big Momma”
“Big Momma”, a 330-year old mountainous star coral found in Southeast Florida, was the largest known colony of Orbicella faveolate. Despite having survived numerous hurricanes, the industrial revolution and the rapid urbanization of the Florida coastline, this iconic coral structure died within only three to four months of contracting this tissue loss disease.
If you would like more information on identifying infected corals, check out this presentation by Andy Bruckner from NOAA, September 2020.
How To Prevent The Spread Of The Disease For Recreational Divers:
In addition to identifying diseased corals, it is also important for divers to be aware that they may act as vessels of transmission, as the pathogen is able to survive on diving gear, such as wetsuits and snorkels.
- Never touch the coral reefs – as the disease can be spread through contact, it is important to prevent the transfer of disease causing pathogens between different corals.
- Try rent gear locally – this will help to prevent the transfer of pathogens between different reefs.
- Dive on healthy reefs before diving on infected reefs – this lowers the risk of transferring pathogens between dive sites. If you’re unsure about which dive sites are infected, try asking the local dive club or go check out the SCTLD Tracking map on the Atlantic and Gulf Rapid Reef Assessment website.
- Rinse your equipment in a 1% bleach solution, then water, and it allows it to dry fully after diving at an infected reef, as this will kill any bacteria on the equipment.
Another important way to help out is to spread awareness of the disease to your local dive community, and also to your family and friends. By raising awareness of the disease, the more people are likely to get involved, and the bigger the overall impact will be. Coral reefs are indeed highly threatened, but it is not too late to save our reefs and all the creatures that depend on them.