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Photo: Valeria Pizarro
The Varadero reef has survived in Colombia’s Cartagena Bay despite toxicity from heavy shipping. The corals grow twice as fast as similar corals elsewhere, but their skeletons are less dense, which may have something to do with their success.

The news about coral reefs has not been good for a long time. Rising temperatures and too much carbon dioxide have been killing off these delicate creatures worldwide, with dire consequences for the marine life that depends on their intricate communities.

But what is going on in Cartagena Bay? Elizabeth Svoboda has a fascinating story at the Christian Science Monitor.

“For the coastal communities that have harvested its bounty for centuries, and for the scientists who officially discovered it five years ago, there is no reef like Varadero. Locals call it ‘the improbable reef,’ and for good reason: It has persevered in the midst of intensive coastal development, streams of toxic runoff from the nearby Canal del Dique (Dike Canal), and waters so warm they’d turn many reefs into lifeless skeletons.

“Scientists like Lizcano-Sandoval and Pennsylvania State University’s Mónica Medina are working to uncover the secrets of Varadero’s striking resilience – secrets they can use to help other threatened reefs around the world.

“But just as Varadero begins to yield its tantalizing scientific bounty, it’s looking as if the reef may be damaged or even destroyed. A group of government officials, port authorities, and businesspeople is planning to dredge a channel so Cartagena’s harbor can accommodate more container ships – a move they say will boost the nation’s economy. However, the researchers who study Varadero, along with local environmental activists, are hoping to stall the dredging project so the reef’s storied legacy can continue – and perhaps contribute to the rescue of other endangered underwater Edens. …

” ‘Corals in Varadero have a very distinct growth pattern,’ says biologist Roberto Iglesias-Prieto, Dr. Medina’s colleague at Pennsylvania State University. Specifically, the corals grow about twice as fast as similar corals elsewhere, but their skeletons are less dense; it’s possible that these traits give them an advantage over their slower-growing coral counterparts.

“Medina thinks certain elements in runoff from the Canal del Dique may be benefiting the corals in surprising ways. ‘Part of the day, [the corals] get these nutrient-rich waters where they’re eating and photosynthesizing,’ Medina says. She notes that fairly recent changes in coral growth coincide with a period when more sediment was being dumped into the bay. …

“Varadero’s corals might also benefit from their location right at the mouth of Cartagena Bay. “They have constant communication with the sea,” [Dr. Valeria Pizarro, who discovered the reef,] says. The fresh inflow of ocean water might lessen the impact of toxic mercury, cadmium, and copper that runs off into the bay from nearby industrial facilities.

“Medina and her colleagues are trying to figure out if other aspects of the reef’s biology contribute to its success – aspects that could ultimately be replicated in reefs elsewhere. … Samples of microbes from Varadero’s corals – the onboard collection of bacteria, viruses, and algae that perform critical metabolic tasks – have revealed that they are totally distinct from those found on other reefs, Medina says. Her lab is conducting a detailed analysis to find out whether the microbes might be performing important functions, such as fighting disease, that help the corals to survive even in less-than-ideal conditions.

“In the future, if conservationists can transport Varadero’s hardy corals to other endangered reefs around the world, or even seed threatened reefs with whatever microbial cocktail helps Varadero’s corals thrive, those reefs might have a better chance of surviving despite ocean warming and pollution. Many of the world’s reefs now hang in a liminal zone between death and survival. By putting Varadero corals’ survival tactics to work on other threatened reefs, scientists like Medina, Lizcano-Sandoval, and Pizarro hope to tilt those reefs a little bit closer to the side of life.”

More at the Christian Science Monitor, here.

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