SILENT KILLER SPREADS - Deadly Coral Disease Out of Sight, Out of Mind for Many

Tue, Mar 16th 2021, 10:44 AM

First verified in The Bahamas a year ago, the deadly Stony Coral Tissue Loss Disease (SCTLD) continues to plague Bahamian waters, traveling up to 50 meters (55 yards) per day, killing hundreds of corals in its wake.

Specifically, scientists from the Perry Institute for Marine Science (PIMS) have confirmed the presence of SCTLD on reefs off Grand Bahama, New Providence and North Eleuthera. Early assessments done by PIMS suggest that some species are more susceptible than others; brain corals, for example, are particularly susceptible to infection and often die within weeks.

“The reality is, the disease is spreading and it’s spreading very fast,” said Dr Valeria Pizarro, a coral reef specialist and senior scientist at PIMS. “If we lose those species which build up coral reefs, we might lose coral reefs in the long term with profound ecological impacts,” she said.

The lethal reign of SCTLD
Although evidence suggests the outbreak of SCTLD began off the coast of Florida in 2014, the first case of the disease was not confirmed in The Bahamas until March 2020. That’s when PIMS scientists discovered SCTLD had already killed a wide range of corals off Grand Bahama, including some species listed as endangered by the International Union for the Conservation of Nature (IUCN).

Less than three months later, PIMS confirmed the presence of SCTLD in coral colonies off New Providence. There, many corals harbored the tell-tale signs of white, exposed, skeleton patches associated with the novel disease.

SCTLD has also been reported but not verified in Abaco and the Exumas, said Dr Pizarro who in 2019, worked in Eleuthera as a partner in The Bahamas Coral Innovation Hub, a project that aims to expand and improve coral restoration in The Bahamas. Worse still, the disease affects more than 20 hard coral species in the Caribbean.

“I’ve been diving since I was a teenager and I’m now in my 30s, and I’ve never seen so much coral death,” said Dr. Krista Sherman, a fellow senior scientist at PIMS. “It’s depressing.”

Glimmers of hope
The recent discovery of an underwater treatment for SCTLD, however, gives hope to ocean conservationists like Dr. Pizarro. In Florida, coral researchers are already administering life-saving antibiotics onto struggling corals, with high rates of success.

Once PIMS receives approval from the Bahamian government, Dr. Pizarro will train local partners and begin the same treatment here in The Bahamas. Currently, there are enough doses to treat 1,000 infected corals, but time is quickly running out.

“Our supply of treatment is about to expire, so we really can’t wait much longer,” Dr. Pizarro said.

The team also has another challenge – deciding which corals will receive treatment. “The only limitation is that we can only treat so many corals. We cannot say that we are going to treat every single coral because not only does it get expensive, but it’s also labor intensive. There are hundreds of thousands of corals and we can only treat so many. A team of six trained persons could treat “a couple hundred” corals per day. So, we will have to prioritize where we are going to deliver treatment and which species we are going to target. This is being discussed within the SCTLD Task Force.”

While coral diseases are not uncommon in the tropics, SCTLD is in a league of its own because it spreads rapidly, kills quickly, and many coral species are susceptible to it. According to the Reef Resilience Network, it has spread to nine countries and territories in the Caribbean region.

Coral reefs are home to 25 percent of the ocean’s fish and provide essential coastal protection from hurricanes and storms. Aside from antibiotic treatments, some regions are racing to outplant thousands of low susceptibility corals onto local reefs to thwart the negative impacts of SCTLD.

“Another strategy that has been effective in other places, especially in Florida, is to create lab-based nurseries or use biosecure facilities where you can rescue and safely house hundreds or even thousands of corals that you can use to later repopulate coral reefs.”

How can you help?
In the meantime, Dr Pizarro urges “everyone that’s getting into the water to get involved.” To prevent further contamination, ships should discharge ballast or bilge water where they picked it up or far away from shore to avoid reef contamination. Other preventative measures include treating bilge water to kill all microbes and decontaminating fishing, diving and snorkeling equipment to avoid the spread of SCTLD by humans.

“We need as many people as possible sending us photos and information so we can prioritize which places we need to visit. We have to stop the spread.” To report SCTLD in The Bahamas, visit PIMS’ website at http://www.perryinstitute.org/reportsctld/

The symmetrical brain coral, Pseudodiploria strigosa in New Providence, healthy (left) and affected by Stony Coral Tissue Loss Disease (right). The white area of the coral is already dead as the disease advances throughout. The time lapse between the first and second photo is approximately one month.

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