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Coral reefs are dynamic ecosystems full of color and complexity.
Photo: Genevieve Johnson

March 20, 2003
Coral Reefs - An Underwater Paradise
  Real Audio Report

Log Transcript

The Maldives is an underwater paradise in an area where the vast blue reaches of the ocean are studded with coral reefs. These reefs stretch for almost 900 kilometers, harbouring an explosion of aquatic life that includes over one-third of the reef fish found in the entire Indian Ocean.

Estimated to cover far less than 1% of the world's oceans, coral reefs posses a biodiversity so rich that they may be home to nearly 25% of all marine fish species. Over 2,000 reef fish species are found in the Maldives. These underwater coral cities are alive, growing, producing food and providing shelter and habitat for reef dwellers.

Corals are made up of individual living animals or polyps. Because animals cannot convert the suns energy into food, they house solar collecting plants called algae. Solar energy from the sun is converted into food that is shared with the coral animal host. This symbiotic coral-algae relationship benefits both parties - the more food the algae provide, the further the corals are able to grow toward sunlight. The waste products produced by the coral animals are recycled by the algae and are in turn, used for growth. This is the power source that drives all life on the reef.

A brightly colored young, Coral Grouper.
Photo: Genevieve Johnson

The main reason for the abundance and variety of life is that water surrounding the 1,100 islands that comprise the archipelago, provides an assortment of habitats that suit the individual needs of an exceptional number of species. Barrier reefs rise abruptly to the surface from 2,000-3,000 meters below and are dashed by waves and currents. This is where the larger pelagic species congregate, including tuna, barracuda, trevally, manta rays and sharks, sometimes even the whale shark-the largest fish in the sea.

Tranquil shallow lagoons, dotted with enormous coral heads and plateaus are bathed in clear, calm waters warmed by the tropical sun. Life below the surface consists of a thriving metropolis of creatures. The continual growth of the corals is matched by the death of the polyps in the lower layers, which are transformed into calcareous rock. The myriad of cracks and crevices that form among the rocks are a perfect refuge for many, including moray eels, groupers, goby's, parrotfish, butterflyfish and triggerfish.

The other day the crew took the opportunity to dive on the splendid coral reefs of the Maldives. Gliding above the multihued community of a healthy coral reef system is an experience unlike any other on this planet. New marvels appear around every corner, beyond each wall, under every overhang and above each pinnacle. There are an infinite number of areas to explore. The designs and patterns appear endless in a world where color and shape seem intent upon causing confusion. Even when only inches away from a butterfly or a scorpion fish, it takes a few moments before you are actually able to focus on the animal and distinguish it from the background of the reef. Every second of every minute beneath the surface of the sea is dazzling; there is no possibility of boredom or repetition.

We noticed that several species were far larger and less timid than almost any other area of the world we have visited. Perhaps this is due to the fact that the reefs are well protected and spear fishing is illegal in the Maldives. The fish have not learned to be weary of humans!

A Black-saddled pufferfish hides in the elongated arms of a soft coral gorgonian fan.
Photo: Genevieve Johnson

The crowded and elaborate nature of coral reefs means that creatures have learned to co-exist, while many have developed complex relationships, perhaps the best known being that between the anemone and the anemone fish. Another relationship that features regularly around the reefs is that between the cleaner wrasse and its clientele at cleaning stations. Fish wanting to be cleaned or groomed approach the area displaying behaviour patterns that clearly express their desire to be cleaned. The cleaner wrasse answers the call and immediately approaches the customer. With gills open and jaws extended, the fish invites the cleaner to remove any parasites and food residue. The wrasse gets a free meal, while the customer is cleaned of any pests. When we remained motionless while observing the stations, the cleaner wrasses inspected us as well.

The intricate nature of coral reefs may also be their undoing. Take away the triggerfish and there will be so many reef boring sea urchins that the very foundation of the reef weakens. Remove the groupers and the algae will flourish, smothering the reef. Take away the napoleon wrasse and the coral eating crown-of-thorn starfish will consume the living coral. While it has taken millennia for these incredible structures to form, their destruction can take place overnight. The careless hand or fin of a diver, a misplaced ships anchor and too much sewage flowing out from a coastal town can destroy coral reefs that have taken centuries to build. We are all responsible for protecting coral reefs.

Because coral reefs are so sensitive to even the slightest environmental changes and respond to stimuli such as sea temperature change so quickly, many scientists liken them to an early warning system of the health of the planet. Recent estimates indicate that more than half of the world's coral reefs are in danger of being lost due to human activity and sea temperature rise.

This is Genevieve Johnson speaking to you from the Odyssey in the Maldives. Join me for the next Odyssey log when we explore the impact of sea temperature rise on the world's fragile coral reef systems.

A spotted Sweetlips waits patiently at a cleaning station, while Cleaner Wrasse remove parasites from its gills and mouth.
Photo: Genevieve Johnson


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