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How Pollution Affects the Health of Coral Reefs
Narrator: Worldwide, tropical reefs are among the most threatened of marine environments.

In the Atlantic Ocean, once vibrant Caribbean corals are dying as diseases spread over wider geographical ranges. The die-off is extensive for major species of reef-building corals. And in decimated areas, sediments and seaweeds replace them.

Off the Atlantic coast of Panama, near it's border with Costa Rica, are the islands of Bocas del Toro. These lush, green tropical islands are in an isolated area of Panama that have some of the most unspoiled coral reefs in the Caribbean. Only a few thousand people live in Bocas' town and surrounding villages. But during the past decade, international travelers have discovered the area, resulting in increased population and development that threaten the environment.

The Panamanian government and the residents of Bocas are proactive about preserving their paradise, so they are working with concerned scientists from around the world. Among the researchers here is a graduate student from Scripps' Center for Marine Biodiversity and Conservation. Davey Kline is studying how changing environmental conditions are affecting coral reef habitats and what the future may hold.

Davey Kline: The reefs are in an incredibly sad state. In the next 20 to 30 years, if things continue as they're presently going, it's possible that there will be no more healthy Caribbean reefs at all. And I'm trying to figure out how all of the things that we're putting into the ocean - the sedimentation associated with cutting down rain forests, the pesticides from farming, the sewage that dumps out into the ocean, the oil from boats - how each of those things affects the coral animal and more specifically, how it affects the relationship between the coral and the symbiants that live within the coral.

Narrator: Davey Kline has been living in Bocas del Toro for over a year, working at the Smithsonian's Tropical Research Institute. The Smithsonian has several research stations in Panama and for 50 years, has worked to protect the country's natural resources. Its labs, facilities and housing are available to scientists from around the world.

The dock at Bocas del Toro gives quick access to the local waters. Neilan Kuntz, a Smithsonian research associate, assists with the project. They're setting up for a collection dive off the main island at Punta Caracol, a diverse reef in 15- to 20-feet of water. Davey enters to snorkel around on the surface and pinpoint the good collecting area.

They are seeking Montastraea annularis, or mountain star coral. It's one of the most common reef-building corals in the Caribbean and the Gulf of Mexico. Each coral colony is made up of thousands of tiny, individual animals called polyps that are basically a mouth surrounded by tentacles. Polyps produce a covering of thick mucous that is constantly shed from the coral.

The mucous supports a diverse community of bacteria that differs between species of corals. This mucous also serves as the coral's first line of defense against disease. Davey places a syringe on individual polyps to suck off mucous to take back to the lab. Notes are taken about the health of the coral and the mucous samples are marked and numbered.

As their experiment requires living coral, Davey looks over the colony for a healthy sample of the right size. He selects a piece where he can chisel on dead skeleton to avoid damaging any living tissue. The coral colony needs to be flat on the bottom, so it is trimmed with bone clippers. Again - just cutting the dead skeleton.

Back on the boat, Davey and Neilan examine the samples to check their suitability. About 40 polyps are on this small piece. Despite the extensive damage caused by coral disease, very little is known about what causes them. Of the 27 reported coral diseases, the causes are known for only a few.

They head back to the Smithsonian's dock. Here, the corals are placed into a one-of-a-kind aquarium that accommodates 400 samples simultaneously. Designed by Davey and Forest Rohwer of San Diego State University, the system exposes the corals to precisely-controlled stresses while mimicking the conditions of the reef. Filtered reef water is pumped into the system and mixed with various concentrations of nutrients, chemicals and bacteria. They are taken from sewage, asphalt and other pollution sources.

Davey Kline: This concentrated chemical is then mixed with the sea water and the dose sea water travels down these lines to what we call an accumulator. And what the accumulator does is then distribute the water to the ten replicate corals and then we can look at the effects of the chemical on these coral. We can look at 40 independent chemicals on 400 corals and we can get an idea of what levels of the different stressors affect the corals and how it changes the relationship between the coral and their bacterial and algal symbiants.

Narrator: A healthy coral colony has a rich brown coloring from it's symbiotic algae, while a diseased one is bleached white.

In the Smithsonian's laboratory, the mucous samples are prepared. The bacteria in the mucous are introduced into a specific growth medium in Petri dishes. Sterile techniques are used to ensure no contamination.

The experiments have shown that very low levels of chemicals and nutrients can stress the corals and their symbiants. The dishes are placed into an incubator, where the warm temperature will allow the bacteria to flourish over the next three days. When they are removed, the dishes contain a thick soup of bacteria, which is transferred into vials of sea water.

Neilan then measures the exact bacteria concentration, so that they can control the doses added to the corals in the experiment. Davey prepares a sample of asphalt from a local road. Small chunks are broken off and placed into a porous bag. The oils and tars in asphalt and roofing materials dissolve in water and their run-off is one of the major problems of urbanization near coral reefs.

Back at the experimental aquarium, Neilan mixes a bacterial solution into the system. The research is showing that some coral diseases are caused by a loss of balance among bacteria species living on the reef. Davey takes a packet of asphalt and puts it into another container. They found that asphalt kills corals quickly and are trying to determine which compounds are the least toxic, so recommendations can be made about future road and building materials. The greatest concern is that people who live near coral reefs, often don't realize how their actions affect the marine environment.

Davey Kline: From my research, it's pretty clear that most of the stuff we're dumping into the water is gonna affect the reefs. And if people don't think about what they do with their sewage water; what they do with the run-offs from banana plantations and from farms that we're going to lose all this diversity associated with reefs.

EDITOR'S NOTE: This video was produced in 2004.