Mote Marine Laboratory

Science to the Rescue: Focusing on coral's future

By: Rebecca Evanhoe

Five thousand years ago, a single coral found its home on a naked ridge of undersea rock near the Florida Keys. New corals of all shapes and sizes — from branched to bulbous — joined the party and gradually the reef developed into a complex, interconnected ecosystem waving with color and life.

Today, the home the corals created is populated by an argyle-like array of fish, giant lobsters, snails, anemones, eels, crabs, shrimp, sea cucumbers, urchins, sea stars and octopus. The reef — the only living bank barrier reef in North America — is visited annually by 3 million divers, snorkelers, anglers, boaters and scientists who come to the Florida Keys National Marine Sanctuary to see or study the brilliant patches of underwater life.

But between the underwater “islands” of life, there are graveyards of dead corals, and the reef’s healthy patches are getting fewer and farther in-between. “People that see the coral reefs in the Keys today, if that’s their first impression, they see the color and they see the fish and it looks absolutely fantastic,” says Billy Causey, the marine sanctuary’s superintendent. “But the reefs I saw the first time in 1957 were considerably different than what we have today. Back then, I saw more coral diversity, more healthy corals, more living coral cover and more marine life.”

While managers and scientists have spent decades focusing on coral disease and destruction, new work looks at healthy coral for innovative ways to stem declines. They’re also considering new methods to restore the reefs themselves. Mote’s Summerland Key Tropical Research Laboratory is a microcosm of new reef research that focuses on the entire reef in order to understand how the system works and to determine how to restore its health, says Dr. David Vaughan, director of Mote’s Center for Coral Reef Research.

This ecosystem-based approach looks not only at individual reef inhabitants, but at the interactions between plants, animals, physical conditions like temperature and chemical conditions like water quality with an eye toward restoring an important marine resource.
But reef restoration is complex. “Notorious for its difficulty,” Vaughan says. “No one’s really done it before.”

Race against time

The reef-building process, which takes thousands of years, is being undone in a fraction of that time. In the last 10 years, 25 percent of the world’s corals have disappeared after being harassed by disease, poor water quality, commercial harvesting and global climate change, according to a U.S. Coral Task Force report from the National Oceanic and Atmospheric Administration. “We’re losing them faster than we can study them,” says Vaughan.

The increasing threats against corals are most likely human-induced. “Coral reefs have existed for 400 million years. It’s the human impact that’s changing the structure of our reefs today,” says Causey.

Like a snail crawling along a backward-moving conveyor belt, corals try to repair themselves in the face of many setbacks. The four big threats to coral reefs are changes in water quality, habitat destruction, overfishing and climate change. The reef’s general health suffers from man-made pollution, particularly excess nutrients from run-off. As the quality of the water — the corals’ lifeblood — degrades, the corals become “stressed.”

“When corals become stressed, the next thing that happens is outbreaks of various diseases,” says Causey. A stressed coral has more difficulty protecting itself from disease because energy goes into maintaining status quo instead of growth.

Boat groundings and dragging anchors can also crash into the reefs — as can hurricanes — shattering reef structures and breaking off hundreds of tiny pieces of coral. “One of the greatest impacts there is the loss of framework — the three-dimensional aspect of the reef itself that is so important to the reef community. Fish and other organisms are attracted to a reef habitat with little nooks and crannies,” says Causey. Fewer nooks and crannies means fewer critters.

Reefs are also overfished and overharvested — commercial industries seek fish and corals for food and saltwater aquariums. Although some corals grow faster than others, most of them grow in terms of millimeters a month — about as fast as human fingernails.

New approach to old problems

Since the 1970s, scientists and reef enthusiasts have decried the need for reef protection. Scientific, technological and governmental advances have made the idea a more realistic possibility. At Mote, scientists from different disciplines work together on different aspects of the coral reef problem.

Dr. Kim Ritchie studies coral bacteria in an effort to learn what it takes for healthy corals to thrive and Erich Bartels and Cory Walter watch the living reef for signs of distress. Dr. Kenneth Leber and Dr. Vaughan consider the balance of the animals living on the reef and what role they might play in restoration and Dave Lackland coaxes delicate corals into growing under artificial conditions, in the hopes that someday they may be used to repair man-made or nature-damaged reefs.

Microscopic helpers

Though the interactions between corals and bacteria aren’t well understood, they may be an essential piece of the reef ecosystem. Dr. Kim Ritchie wants to figure out how corals help themselves through symbiotic relationships — intimate collaborations between two or more different organisms of different species. For example, corals themselves are built of symbiotic relationships between the coral polyp and tiny plant-like organisms that use light to make food. The coral polyp is a very simple animal similar in appearance to a sea anemone. Within the coral polyp live the algae, called zooxanthellae. Although the coral polyp gets its meals by grabbing edible particles that float by, the zooxanthellae provide additional energy.

Corals secrete mucus — a transparent, amber-colored goo — that coats them. The mucus protects the coral by preventing it from drying out and it also prevents ultraviolet light damage from the sun — like sunscreen for corals.

Ritchie’s main focus is the hundreds of species of bacteria that cohabitate in coral mucus and form symbiotic relationships among each other and with the corals. She’s also looking for antibiotics that the bacteria may produce that could protect the coral from disease — or even from other corals.

Ritchie’s non-invasive methods involve snorkel gear and a needleless syringe. She dives to a coral, agitates it to urge it to produce excess mucus, and then slurps the mucus up with the syringe. Back at the lab, Ritchie grows all of the different bacteria on petri dishes to watch their behavior.

“The first thing I look for is whether the bacteria are happy growing in the coral mucus,” Ritchie explains, since many bacteria in the mucus aren’t there on purpose but are actually trapped. Then Ritchie looks for evidence of antibiotic effects; if she finds a bacterium that prevents the growth of another, then she knows the first bacteria produced some kind of antibiotic compound.

She has found bacteria that won’t grow unless they’re neighboring another specific colony — a good indicator that the two have symbiotic or chemical interactions. Ritchie also has found some relationships between pigments and antibiotics; often the pigment — bold orange, or black like India ink — is itself an antibiotic. Such bacterial and chemical clues, once fully understood, will bring another aspect of coral life into focus that can be applied toward the reef’s salvation.

Picking up the pieces

Staff scientist Dave Lackland repairs what’s broken. He takes bits of coral that are orphaned — snapped off by boats or divers — and coaxes them to grow under artificial conditions. It’s no easy task with very picky corals. To heal such slow-growing, fragile creatures, Lackland must perfect technologies for growing coral in aquariums.

The long-term vision for Lackland’s work is to “aid restoration work on areas impacted by man-made or natural disaster,” says Dr. Kevan Main, director of Mote’s Center for Aquaculture Research and Development. “The goal of the coral aquaculture program is to produce fragments of coral that could be put back on the reef.”

“Artificial conditions” does not mean unnatural conditions; Lackland tries to reproduce an environment as close to nature as possible. His persnickety patients are housed in a series of raceways outdoors and in a more complex system of indoor tanks that serve as refuges for battered corals. Tanks are designed to mimic the ocean as precisely as possible in terms of salinity, water quality and light.

Carefully monitored water chemistry isn’t enough to give the corals a true ocean-like environment; corals need waves, too. Attempting to imitate the randomness of wave currents has led Lackland to invent his own hi-tech system. In addition to a standard wave-making pump, he’s got a computer hooked up to mimic random wave patterns. He also has an electronic “eye,” or sensor, posted outside of his laboratory that triggers waves inside the tanks so the random passing by of a scientist at the lab will cause a sudden random waves in the tanks — similar to a big fish swimming by a coral in the ocean.

Lackland grows 23 coral species to help safeguard the assortment of reef life. “What I worry about is some of these rare corals that provide the diversity,” Main says. “There are maybe 10 species that can reestablish themselves after disaster. But what about the other 40 that are more sensitive or grow slower? It took 1,000 years for that coral to find its spot on the reef. If it wasn’t for aquaculture, we might lose those species all together.”
 

A unique system

The Keys reef tract runs in a ridge line for 220 miles alongside the dotted line of the Florida Keys. Their location makes them a most unusual system.

The corals inhabit the intersecting waters of Florida Bay, the Gulf of Mexico and the Atlantic Ocean, which creates one-of-a-kind ocean currents, weather patterns and water conditions.

The Keys reefs have 107 species of corals — that’s 80 percent of the known coral common to the tropical Atlantic — and more than 500 species of tropical fish. These reefs are not only a rich, valuable bank of species; they also contribute to the surrounding ecosystems of mangroves and seagrasses.

Coral reefs also serve as nursery grounds for baby fish as well as being breeding grounds for adults. Their disappearance would have devastating effects on sea life in the Gulf of Mexico and tropical Atlantic. The tourism economy — a $1.2 billion dollar industry in the Keys that contributes to the state’s tax base — and the commercial fishing industry — the Keys reefs alone accounts for $50 to $70 million worth of commercial catch each year — would also suffer.

Distress signals

Cory Walter, staff biologist, plays the role of shepherd; she watches corals “in the wild” for a major symptom of stress and damage called bleaching. The bleaching process is a literal drain of color from the corals. The whitening occurs when the colorful zooxanthellae that live within the corals are lost. What remains is a colorless framework — a hard, white skeleton of calcium carbonate, the same compound that makes up chalk and clamshells.

Walter and community observers — divers, boaters and snorkelers — keep an eye out for bleached coral, steadily increasing in the Keys and worldwide since the 1980s.

The work is part of the Marine Ecosystem Event Response and Assessment Program that Mote Staff Scientist Erich Bartels operates in the Keys. It allows sanctuary visitors to provide information about unusual events they witness in that ecosystem.

“The greatest threat of all on a global scale is climate change that corals have never experienced and we’re seeing this by way of coral bleaching,” says Billy Causey, superintendent of the Florida Keys National Marine Sanctuary. “And it’s not just the bleaching itself but the aftermath of the bleaching, and the stress that comes with bleaching.”

Previous bleaching events “correlated with regional and global bleaching events, which tends to point to the fact that these are considerably widespread,” says Causey.

With funding from NOAA, Walter compares reports on coral bleaching from those who encounter the reefs. She combines the community observations with ocean temperature satellite imagery and in situ monitoring from observation towers in the Florida Keys to produce “Current Conditions Reports” used by other scientists to answer bigger questions. The program’s job is to increase the community’s understanding of what information is out there.

Calling for back up

Another reef “helper” that Mote scientists study is the long-spined sea urchin, Diadema antillarum. These sea urchins are essential to reef health because they eat algae from the corals that, if left unchecked, will overgrow existing corals and prevent new corals from finding places to anchor on the reef. In other words, reefs need their long-spined sea urchins.

“The Diadema is one of the reef keepers; they graze the algae off the coral — sort of the lawn care guys,” says Dr. David Vaughan. “They’re one of the keystone species that help keep the reef clean.”

Urchins are normally abundant in reefs, but in 1983, a disease decimated the populations from the Panama Canal up to Florida, and most populations haven’t recovered. Once thought to be a nuisance, scientists realized — after their absence — that Diadema play a very important role in reef health. “In many places it has come back, but it hasn’t in the Keys,” says Dr. Kenneth Leber, head of Mote’s Center for Fisheries Enhancement, which focuses on scientific restocking efforts. “The result is that we’re seeing more and more of what are called ‘smothering algae.’ ”

Leber, with the help of Mote adjunct scientists Ken Nedimyer and Martin A. Moe Jr., is focusing on the idea of growing Diadema in conservation hatcheries and then re-stocking reefs with their spiny friends. But first, the team must figure out if Diadema can be grown in hatcheries and whether those urchins will be strong enough to survive in the wild. “There’s a lot of work to be done to understand whether this is a good conservation tool or not,” Leber says. “You don’t want to take it lightly.” A plan to put urchins back on reefs is still five or 10 years away but Vaughan and Leber hope that with Diadema’s help, cleaner, uncluttered reefs will encourage existing corals to grow and be an inviting place for new corals to call home, too.

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