Let’s talk Stony Coral Tissue Loss Disease (SCTLD)

Gross morphology of Stony Coral Tissue Loss Disease (SCTLD) in S. siderea (L) and in O. annularis (R), Photos taken by Dr. Andy Bruckner, FKNMS, Looe Key, August, 2018 (retrieved from https://nmsfloridakeys.blob.core.windows.net/floridakeys-prod/media/docs/20181002-stony-coral-tissue-loss-disease-case-definition.pdf, April 10, 2018)

First, yes, this is important for you to know about and yes, it does affect you even if you live in a snow-covered area and it is April. Why you might ask? Well, coral reefs, and particularly the reef building stony corals (Scleractinia), are extremely important habitat for fish and invertebrates including many of the fish and invert species with great economic value such as lobster, grouper, snapper and squid. Stony coral are economically important not only because of the species they provide shelter and protection for, but also because of their importance to the tourism industry. According to the National Oceanic and Atmospheric Administration, the estimated total economic value of coral reefs in the US is $3.4 billion (2013). Worldwide, the estimate is valued at $29.8 billion (2008) with tourism and recreational activities accounting for $9.6 billion. Even if you have never seen a coral reef, you benefit greatly from its existence in the form of fisheries (delicious fish and lobster!), carbon-sequestration (#climatechangeisreal), coastal protection (hurricanes!), biodiversity (marine organisms are amazing!), and tourism which contributes greatly to the economy.

Second, corals are animals that evolved over 500 million years ago during the Cambrian period. They are made up of thousands of individual polyps which form coral colonies and secrete calcium carbonate to build the skeletal structures we know and love; coral reefs. Our economy, safety, food security and existence as we know it are inextricably linked to these magnificent animals!

Sadly, changes in climate due to high levels of carbon dioxide in our atmosphere, increases in ocean temperatures, pollution, and decreases in pH are severely threatening these important animals. Like any animal, coral is highly susceptible to disease stemming from bacterial or viral infection (they can also experience metabolic dysfunction and are highly sensitive to toxicants which can suppress their immune systems). According to Dr. Andy Bruckner of the Florida Keys National Marine Sanctuary (FKNMS), over 40 diseases have been identified in corals throughout the Caribbean. Those affecting stony (hard) coral include Stony Coral Tissue Loss Disease (SCTLD), White Plague Disease, White Band Disease, Black-Band Disease, Red Band Disease, Yellow Band Disease, Dark Spots Disease, and White Patch Disease, and a host of others which lead to tissue necrosis, bleaching and often, death. Each disease has a unique etiologic agent (bacterial, viral, fungal, etc.) and for many coral diseases the etiologic agents remain unknown.

Reported in 2014 by researchers at the Florida Keys National Marine Sanctuary (Dr. Andy Bruckner and team), the Stony Coral Tissue Loss Disease, a relatively newly discovered disease, is quickly spreading throughout the Caribbean.

Third, what exactly is SCTLD? SCTLD is a disease that primarily impacts stony corals. Its gross morphology has been described: “Tissue loss often appears initially on the edge of the colony and spreads upwards and is characterized by newly exposed white intact skeleton that can become covered with algae within 3–7 days. Tissue-loss lesions can also begin as patches or blotches within intact tissue that can increase in size and fuse together.” (National Marine Sanctuary, Florida Keys Case Definition: Stony Coral Tissue Loss Disease (SCTLD) October 2, 2018, retrieved April 10, 2019).

The etiologic agent of SCTLD is unknown.

Stony corals with the highest susceptibility are: boulder brain coral, pillar coral (endangered, Endangered Species Act (ESA)), elliptical star coral, grooved brain coral, smooth flower coral, maze coral, symmetrical brain coral and knobby brain coral (National Marine Sanctuary, Florida Keys Case Definition: Stony Coral Tissue Loss Disease (SCTLD) October 2, 2018). Coral with intermediate susceptibility include: lobed star coral (endangered, ESA), mountainous star coral (endangered, ESA), boulder star coral (endangered, ESA), large-cup star coral, smooth star coral, blushing star coral and starlet coral (IUCN threatened) (National Marine Sancturay, Florida Keys. Case Definition: Stony Coral Tissue Loss Disease (SCTLD) October 2, 2018).

Coral colonies are highly susceptible to disease due to their low genetic diversity. A coral colony is made up of thousands of identical individual polyps. Therefore, if a colony becomes infected, it is likely that the entire colony will succumb to disease. However, some polyps may survive and keep growing.

Fourth, what is being done to stop this disease from spreading throughout the Caribbean? RESEARCH!

Scientists are out every day doing surveys to better understand SCTLD and how it is spreading. Studies are also being conducted in the laboratory to uncover the etiologic agent of the disease through the application of antibiotics to corals grown in the lab. Marine research is extremely difficult and incredibly time consuming which is why it is important to support marine research. Let’s hope the scientific community can find some answers before SCTLD becomes more wide-spread.

Divers, be sure to clean your gear, especially if you are traveling and as always, never touch coral! For those of you on land, reduce your consumption of products containing dangerous chemicals that are lethal or harmful to coral reefs (see my previous entry on sunscreens).

Finally, what changes will you make today to protect coral reefs? How about changing where you shop (see Droppin’ Knowledge entry on ethically sourced clothing options and put a stop to waste water from denim entering waterways)!

We are more connected to coral reefs than we acknowledge. Let’s hope the scientists leading the way can find a solution for curbing this disease.