Last June, I received a note from the co-administrator of Tela’s Marine Protected Area, Antal Borcsok, saying something horrible was happening to Tela’s reef. “The reef is dying,” he wrote.
My heart collapsed because this reef, one so rare and beautiful and poorly understood, had seemed resilient to so much that we’ve thrown at reefs. I could barely conceive of its loss. But, a few days later Antal wrote again. The death was limited to a particular swath of reef. Much of Tela was still as vibrant as ever.
Still, what had happened?
Our first fear was an outbreak of a horrible disease that’s sweeping the Caribbean called Stony Coral Tissue Loss Disease, SCTLD. This disease eats away at the tissue of coral, killing decades old colonies in a matter of weeks. We also speculated that the death could have been bleaching, the condition in which symbiotic algae leave a coral, usually stressed by heat, to starve to death.
But, this death didn’t fit either epidemiology.
Disease seemed unlikely. Pathogens usually are only capable of attacking certain species, although in the case of SCTLD that number is nearly two dozen. But this death was wholesale, not confined to a few or even dozens of species. It was also not not contagious. Once the swath of reef died, no other reefs were affected. The death didn’t spread.
Bleaching also seemed doubtful. The death was confined to a contained swath of the reef. The death was also abrupt in time, occurring over just five days. Bleaching usually takes weeks or months. Satellite imagery did not show changes in temperature coincident with the die off. And it seemed impossible warm water would be confined to just a section of reef.
That made the culprit more-likely something environmental. In 2016 at East Flower Garden Bank in the Gulf of Mexico, a localized death occurred that reminded me of what happened in Tela. Over a swath of reef, corals died in a matter of days. Photos afterward showed colonies covered in thick white mats of bacteria. Divers in Tela reported that the dying and dead reef were also covered in a layer of milky whiteness.
It took nearly four years for scientists to figure out what happened in the Flower Gardens. The answer was a complex interaction of two processes that depleted the water of oxygen, smothering the life that lived there. The first event was heavy river flow from spring rains, which swept a turbid lens over the surface of the reef, shading the sunlight and slowing photosynthesis, which produces oxygen. Coincidentally, there was an upwelling of deep, low-oxygen water, which further depleted the oxygen, choking anything that couldn’t run away. The white mats were bacteria feasting on the suffocated tissue.
It’s possible that there was some sort of upwelling in Tela. The bay is not far from the deepest canyon in the Caribbean, the Cayman Trench, where it’s imaginable that deep oxygen-depleted water surged upward and was swept toward Tela. But without oceanography for the region, we don’t know anything about the deep currents and where they flow. The Ulúa river, which empties near the bay, could have created a lens of turbid water, but there were no rains before or during the episode when the coral died. It seems unlikely that the same unusual environmental conditions that affected the Flower Gardens affected Tela.
The last day of the ACT expedition in October, non-profit board members Tiffany Duong, Heather Kuhlken, and I had the chance to swim over the damaged section of reef. Antal hadn’t been back since the death had struck and he warned us, “It looks like someone poured weed killer on the reef.” He was right. The swath where the coral died looked like it had been doused in poison. It was all tissue-less and brown. Everything was dead. It felt like swimming through a massacre.
The region where the death occurred was where many of Tela’s massive Orbicella faveolata corals grow. These are an endangered species, nearly extinct in other parts of the Caribbean. But in Tela, colonies grow to the size of shed, and we’d taken to calling the largest, Casita. Its girth was about 80 feet and its height over 25 feet. Its age was likely at least two centuries. Had Casita died as well? We followed Antal through the wrecked reef toward the location of the massive colony. Along the way we noticed many large colonies of Orbicella that had been killed, and our hopes for Casita grew dim. And then, in the distance, we saw the familiar silhouette, a cascade of plates that look like Bo Peep’s petticoats.
Tiff, Heather, and I slowed to let Antal investigate first. He approached from the bottom of the skirts, and rose slowly over their top. His shoulders did not slump and he did not drop his head. He reached out as if to pet the giant. Amid the ruin, this ancient had survived.
So what happened? We don’t know. And that’s a tragedy. We don’t know what killed some of the most vibrant corals in the Caribbean. We don’t know how much life and promise was lost in that five day period in June. We don’t know what the consequences will be for the future. Unlike the Flower Gardens, there’s no scientific infrastructure in place in Tela to muster an emergency team to quickly assess any damage–although that is exactly why ACT was formed and what we are working hard to change! When we return to Tela this spring, one of our goals is to take sediment samples to see if there are any markers of contaminants that might offer clues.
Returning to the surface following the dive through the swath of death, we all felt profound sadness and loss. It took a while to process the destruction below, destruction that felt so immense and so invisible. But one of the wisest sayings I’ve heard is this: it’s how you respond. And despite it all, the reef will respond, and so should we.
Within the nooks and crannies of the dead colonies we could see that animals had already moved back in. Jewel urchins and long-spined urchins hunkered down waiting for night to fall so they could cruise the reef. Here and there were sponges, soft coral, and the pink of coralline algae, a precursor to hard coral settlement. Fish still darted among the now-dead architecture.
This death will become an inopportune experiment, one we must take seriously. We will follow its trajectory and monitor what happens next. Will it recover? If so, how? Which species will be the first to arrive, which will be out-competed? Will algae overgrow this reef as it does so many reefs in sickened locations? Or will the nearby healthy reef support its recovery? Will the herds of urchins hold back the onslaught of seaweed, leaving space for coral to take hold? What lessons can we learn from this tragedy? Our job is to wait, watch, and witness. We must ensure that this unforeseen opportunity to learn about resilience does not remain unseen.