ot far off the shores of coastal parks like Biscayne, Dry Tortugas, and Virgin Islands National Parks are the ancient skeletons of dozens of shipwreck victims. These aren’t the remains of pirates from the 18th century who sailed too close to the shore, but rather coral reefs—living creatures known for their hulking skeletons. For centuries, the biggest hazard facing a coral reef was the hull of a wayward ship, but a recent report issued by NPCA’s Center for the State of the Parks reveals that factors like pollution, global warming, and overfishing have become common culprits. But before getting into a detailed description of the prognosis facing coral reefs, let’s learn a little bit more about the nature of the patient.
“Coral are colonial animals that get their vibrant colors from zooxanthellae, algae cells that live in coral tissue,” says Richard Curry, science coordinator at Biscayne National Park. The millions of zooxanthellae (zoh-zan-THELL-ee) cells conduct photosynthesis, generating energy sources that coral can use, while also altering the coral’s chemistry, allowing it to more easily secrete calcium carbonate and build its exoskeleton.
Strap on a snorkel and get a close-up look at a massive boulder coral or a brain coral—so named for obvious reasons—and you’re looking at a skeleton that’s been secreted over the last year or so, building on the mass generated over centuries. Some reefs are older than old-growth redwood forests, and still growing. In boulder and brain corals, a veneer of living tissue coats the outer surface of the skeleton. The branching corals—staghorn and elkhorn—are the two most important reef-building species in the Caribbean, and both are candidates for listing under the Endangered Species Act. Branching corals dominated the shallow areas of most Caribbean reefs until the early to mid-1980s when white band disease decimated populations in Virgin Islands National Park and Buck Island Reef National Monument. Twenty years later, their numbers are still recovering.
Although the outbreak of disease is hard to control and difficult to attribute to a single cause, researchers believe it’s more likely when reefs are exposed to numerous stressors, such as rising water temperatures; boat groundings; fluctuating salinity; and pesticides and other contaminants from power plants and wastewater treatment plants. When such factors conspire against the symbiotic relationship between zooxanthellae and the coral, the zooxanthellae often leave or are expelled, taking with them the coral’s distinctive color—thus the term “bleaching.” Coral can live in this tenuous condition for a short time and could eventually return to health, but as more corals are bleached, death rates generally climb while reproduction rates plummet.
“As marine managers we talk about ameliorating stresses, but some of the major stresses are out of our control,” says Brian Keller, science coordinator with the Florida Keys National Marine Sanctuary. “The population of Florida is expected to double in two generations, which means those human impacts are just going to get worse. So one thing we’re attempting in the Florida Keys is the concept of a national marine sanctuary—a fully protected area that aims to return these waters to an ‘unfished’ state, to get back the large top predators, the reef fish populations, and lobsters in the hopes that a restored ecosystem will improve the whole system, including the corals.”
Unless you own SCUBA gear and a time-share in the Caribbean, you might be asking yourself: What’s so important about coral reefs, anyway?
“Coral reefs account for less than 1 percent of the Earth’s surface, but they house 70 percent of the Earth’s marine organisms, so you can imagine the consequences of losing them,” says Curry. Indeed, more species of fish alone exist in Biscayne National Park than all the fish, amphibians, reptiles, birds, and mammals in Yellow-stone. Coral reefs have plenty to offer land lubbers as well, as potential sources of new medicines to cure cancer, arthritis, bacterial infections, heart disease, and viruses. Coral reefs even buffer shore-lines against waves, storms, and floods; without them, parts of Florida would be underwater.
If it’s a challenge to prevent damage to coral reefs, it’s equally difficult to repair the damage once it’s been done.
“When a vessel has destroyed an extensive area, coral reef biologists will often collect living coral colonies from surrounding reefs, then transplant those colonies to the restored area,” says Curry. “But in reality, they’re simply causing damage in one area to repair damage in another, which doesn’t make much sense. So the Park Service started a coral nursery: We go to grounding sites and rescue all the coral fragments that are too small to be reattached, bring them into a controlled environment—like a typical plant nursery—and grow them until they can be returned to a natural reef, so we can restore the damaged area without sacrificing surrounding reefs.”
Because many Caribbean corals grow about as fast as continents move, it could take as long as ten to 15 years to return rescued corals to the marine environment. The hope is that the search for a cure will outpace the causes of mortality. Otherwise cold, lifeless skeletons at the bottom of the ocean may be all that’s left behind.
Scott Kirkwood is senior editor for National Parks magazine.
Not far off the shores of coastal parks like Biscayne, Dry Tortugas, and Virgin Islands National Parks are the ancient skeletons of dozens of shipwreck victims. These aren’t the remains of pirates from the 18th century who sailed too close to the shore, but rather coral reefs—living creatures known for their hulking skeletons. For centuries, the biggest hazard facing a coral reef was the hull of a wayward ship, but a recent report issued by NPCA’s Center for the State of the Parks reveals that factors like pollution, global warming, and overfishing have become common culprits. But before getting into a detailed description of the prognosis facing coral reefs, let’s learn a little bit more about the nature of the patient.
