Florida’s devastating coral disease has spread to Caribbean: scientist

Coral Tissue Loss Disease - white-plague disease coral disease FWC - stony coral tissue loss disease

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A white-plague disease infected coral. By William F. Precht.

A devastating coral disease that started in the Miami area has spread to nearly all of the Florida reef tract and the infection known as stony coral tissue loss disease can now even be found as far away in the Caribbean as Mexico, Jamaica, the Dominican Republic, the U.S. Virgin Islands and St. Maarten.

In 2018 coral disease researcher Greta Aeby told WMNF that this is one of the most extensive coral disease outbreaks ever.

Also in 2018 another scientist, William Precht, warned that nearly all individuals of certain coral species have died from the disease and that “in some areas, this is essentially equivalent to local extinction, an ecological extirpation of those species.”

When WMNF reported on this coral disease outbreak in 2016, it had spread from nearby a dredging project at PortMiami to Martin County in the north and to the northern part of the Florida Keys National Marine Sanctuary in the south. But now it has spread all the way to Key West and beyond.

Our guest on WMNF is a scientist in St. Petersburg, Rob Ruzicka. He is the Coral Reef Research Program manager at the Fish and Wildlife Research Institute (FWRI), which is a branch of the Florida Fish & Wildlife Conservation Commission (FWC).

Listen to the interview here:


“We refer to this disease as the stony coral tissue loss disease, as you introduced. And it’s a necrotic condition that some of the laboratory diagnosis shows that it begins from the inside out of the corals. So it actually begins underneath the skeleton, the initial lesions, where they occur, and then it begins to work its way on the outside of the skeleton. And what can happen is when the lesion moves to the outside of the coral, you begin to see either a banding pattern, or a blotchy white pattern, and this will spread across the coral in a relatively quick amount of time. And if that banding pattern progresses across the coral colony, it actually kills the living tissue as it moves across. And the tissue begins to either slough off — or come off the coral — as it’s being killed by the coral. So what will happen, is you will then see the white bare skeleton that is left behind, that won’t actually have any of the living tissue of the coral left.”

When the coral dies from this disease, what does that do to the reef?

“Well, the problem with it is, in terms of the stony coral tissue loss disease event — just taking one step back in the bigger picture. Coral epidemics and coral diseases have occurred before. We’ve been seeing them occur since the 1980s, and we have seen Caribbean-wide disease events happen. But in the past, they’ve generally targeted one or two species of coral at that time. And the disease event or the epidemic occurs maybe for several months or a year. What’s been different about the stony coral tissue loss disease event is we’ve observed lesions on more than 20 different species of coral. So that’s nearly half of the coral species that actually live on the Florida Reef Tract, and that’s what’s so devastating about this. Now, within those 20 species of coral that are affected by this, many of them are the primary architects and principal reef builders that have created our reefs over thousands of years. And, so, when these corals get these lesions, and the entire colony is actually killed or destroyed, we’re going to lose that framework and that habitat that provides homes and places for all the other fishes, many of the other invertebrates that occur on the reef, so we’re going to lose that habitat complexity and those homes for all the other organisms on the reef.”

How and where did this coral disease begin?

“This disease was first observed and documented by colleagues of ours in 2014 in South Florida, specifically in the Miami-Dade and Broward County area where the first corals with lesions that were documented. And then since then it’s persisted. It’s now a five-year event, and it has moved to about 75% of the Florida Reef Tract.

“So, there’s no smoking gun that we have identified in terms of what the origin or the exact cause of this outbreak was. At the time, in 2014, there was a mass (coral) bleaching event that was just beginning at that time. And that would become a global event in 2014 and 2015 with the conditions there. So we did begin to see a lot of bleaching. Corals in Florida, in general, are in a perpetual state of stress and have been for decades. There was also some extensive coastal construction activities that were going on at that time. The Port of Miami was performing its dredging to deepen its port for Panamax vessels. So there could have been a confluence of stressors that were occurring either because the water quality conditions, coastal construction activities, thermal stress that was occurring in the water. And it could be a confluence of all these different stresses that could have created the start of this event.

“Now where we are five years later is that the disease has spread northward and encompassed all of the northern portion of the Florida Reef Tract going up to Martin County and our most recent observations and reports have found it off of Key West. That’s why I say that it has encompassed about 75% of the Florida Reef Tract at this time.”

And for people who might not be familiar, there are reefs in the Florida Reef Tract even beyond Key West.

“Yes, yes that is correct. So we’re keeping a close eye because it has been slowly progressing westward over the course of the last five years and we would still have reefs in the Marquesas Islands, and then, of course, to the west of that, you would also have the Dry Tortugas.”

A guest on my show last year, coral disease researcher Greta Aeby, said that this is one of the most extensive coral disease outbreaks ever. How do you feel about that strong of a statement?

“That is 100% accurate statement by Greta. For one of the reasons that I mentioned, we’ve never seen a disease outbreak affect this many species at one time. And, nearly half of the species in Florida have developed lesions and died with it. Another characteristic of this disease event that’s very unfortunate is how rapid the lesions occur. So when you have massive bleaching events and some other stressors that have affected corals, you can have survivorship or partial mortality on that individual coral when it’s exposed to the stressor and it either bleaches or it has disease. What we found with this disease event is that it is extremely lethal.

“So the most susceptible species that succumb to this pathogen, they endure complete mortality.  There’s very, very few survivors that get the disease and then recover from it. So that’s also made this extremely devastating.

“I oversee one of the long-term monitoring projects for the coral reef evaluation monitoring project here at FWC and in collaboration with our partners at Nova Southeastern and the Southeastern Coral Reef Monitoring Project. These are two of the longest tenured monitored projects in Florida, and we have over 60 sites throughout the Florida Reef Tract. And for those most susceptible species, we’ve seen reductions in their populations on the order of 90 to 95%. So for some of these species, it’s so devastating because they’re being removed from the reef tract. We’ve found a few small surviving colonies, but at this level, some of those species will go ecologically extinct along the Florida Reef Tract if something is not done.  And therefore, that’s why we agree that this is probably  the most devastating event that we have observed.”

A scientist that I have talked to about this coral disease over the last few years, William Precht, warned us that nearly all individuals — as you were saying — of certain coral species, have died from this disease. And he says that is some areas this is essentially equivalent to ‘local extinction of species and ecological extirpation of those species.’

“Yes, that is correct. What we have found through our research programs is that many of the larger, older colonies that are those principal framework builders and architects of the reef, they have been the ones that are the most vulnerable to this event. So, we are losing these very, very large colonies. The ones that survive are very small, and what that means is that you’re removing all the parental colonies across the reef tract. So the recovery is going to be very limited because, number one, you have very few corals that are mature and have the ability to be able to reproduce and provide larvae to help the [reef] recover. And then number two, these smaller colonies, they’re going to take time to become sexually mature and be able to reproduce. And, they’re going to be so spread out far across the reef. Corals, when they broadcast spawn, they’re mixing their eggs and their sperm in the water column. But they might be so far apart that that recombination and those processes that take place in the water column might be unsuccessful. So the ability for them to be able to repopulate themselves and recover naturally, because of those consequences, is going to be very, very difficult. So that there needs to be other actions that are going to need to be taken to help those corals recover.”

These corals you are talking about, these large ones that have been devastated, and the small ones that will take a while to recover, how old were those old coral colonies, the giant coral colonies that are dying? How long has it taken to build those up?

“Well, we know from some of our colleagues from NOAA that have done cores and actually  tried to age those corals, that larger ones that — say, could be the equivalent of like a small Volkswagen Beetle — those corals can be 300 to 400 years old.  Corals are extremely slow-growing organisms that take hundreds of years to be able to build their skeletons and get to the size that they are.  On the other end of this, when we see the lesions develop on these corals, then spread across the individual colonies, this pathogen can kill a large coral like that within a matter of months.  So that’s why we’re so concerned about the future because of the amount of time that it’s going to take for these corals to be able to grow to a size that they can actually reproduce.”

And based on what you said, that’s not just a couple of years. That might be decades and decades.

“That’s right.  That’s correct.”

So, if I’m sitting here listening to my radio.  I’m driving around the Tampa Bay area.  I’m in Lakeland, or Brooksville, or Sarasota.  I don’t have a coral reef outside my door. I don’t run a dive shop.  Why should I care, as someone living in the Tampa Bay area, that there are coral species, lots of coral species, that are possibly going locally extinct in the Florida Keys?

“Well, there are lots of people in Florida that love to visit South Florida or the Florida Keys for their recreational activities.  And whether that is going SCUBA diving, or to go observe the magnificent reefs in South Florida, and go see all the corals and the fishes and the lobsters that live on that reef, for consumptive or non-consumptive activities.  There are millions of jobs that are dependent upon those coral reefs.  And we have millions of citizens that love to visit those locations for a variety of reasons.  And so those environments, those habitats, are going to fundamentally change. Without the living reef structure, we could see changes to the associated populations, whether that would be fishes, or whether that would be lobsters.  So it would have a downstream effect that would be analogous to if you lose all your old-growth trees in a mature forest.  That’s going to have dramatic effects to the bird populations that live within that forest.  There are people all around the United States that love to visit the Florida Keys, and go to Miami and Broward, and experience those reefs.  We know this will also potentially effect what you like to order at restaurants, because those reefs provide a supply of food, and a variety of food for things that people enjoy.  Those are some of the direct and indirect impacts of the loss of some of these corals.”

I want to ask you about the cause of this [stony coral tissue loss disease].  Has the cause or the pathogen that causes it been determined?

“As of this time, no, it’s not conclusively determined.  We have some ideas and beliefs that it could microbial or bacterial in nature.  Both laboratory experiments and in the water, in the field experiments, have shown that the corals respond to antibiotic treatments that have been applied.  So that would provide some evidence that it could be bacterial in nature.  But other laboratory diagnosis have also suggested that it is a consortium of different pathogens that could be taking place on these lesions.  So you could have bacteria, you could have viruses, you could have other organisms within that consortium.  And so, we don’t necessarily know if the primary or secondary infections that take place on these animals is viral in nature or is bacterial in nature. We do know that it is some consortium of that. There are still many scientists that are actually working to try to finalize, and hopefully be able to identify what the exact pathogen is.  But it’s been very difficult to date, to say the least.”

Thanks to Blannie Whelan for help with interview transcription.

At the beginning of the show we talked about bills moving through the Florida Legislature and we heard from people commenting about Thursday’s show.

Listen to the full show here.

Here are three stories WMNF News has done on this coral disease outbreak over the last few years:

Historic coral disease outbreak spreading in Florida

Several coral species could go locally extinct in Florida from white-plague disease

Florida’s coral disease outbreak is most “extensive” ever: scientist