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Turning the Sea Pink
On coral reefs around the world, scientists and divers alike watch for an amazing yearly phenomenon – a night when the ocean waters turn pink. This spectacle occurs during a mass spawning when many species of coral release billions of colorful particles into the water.
Using the lunar cycle and other indicators, the corals in an area coordinate their release of huge amounts of sperm and egg cells on a single night. The cells are buoyant and float to the surface, where they form clouds of color, or “slicks,” that give the water a pinkish-orange appearance. Once an egg is fertilized, it develops into a free-swimming coral larva, called a planula. If a planula isn’t gulped down by a fish, it eventually settles on the sea bed, where it grows into a coral polyp, starting the new generation of reef-building corals.
Aside from the amazing visual phenomenon, this mass spawning technique helps ensure coral survival. Scientists have found that coral eggs can “recognize” and usually reject sperm from their own colony, since corals from the same colony are genetically identical. To form a new, genetically unique organism, a coral egg must be fertilized by sperm from a different “parent” coral. New combinations of genes give corals a better chance of adapting to changing conditions in their environment.
Sometimes, coral eggs are even fertilized by sperm from a slightly different species of coral. This process, called hybridization, allows for even more genetic combinations. Researchers think this is one explanation for the amazing variety of coral forms – a diversity that makes coral reefs some of the most amazing places in the ocean.
Using the lunar cycle and other indicators, the corals in an area coordinate their release of huge amounts of sperm and egg cells on a single night. The cells are buoyant and float to the surface, where they form clouds of color, or “slicks,” that give the water a pinkish-orange appearance. Once an egg is fertilized, it develops into a free-swimming coral larva, called a planula. If a planula isn’t gulped down by a fish, it eventually settles on the sea bed, where it grows into a coral polyp, starting the new generation of reef-building corals.
Aside from the amazing visual phenomenon, this mass spawning technique helps ensure coral survival. Scientists have found that coral eggs can “recognize” and usually reject sperm from their own colony, since corals from the same colony are genetically identical. To form a new, genetically unique organism, a coral egg must be fertilized by sperm from a different “parent” coral. New combinations of genes give corals a better chance of adapting to changing conditions in their environment.
Sometimes, coral eggs are even fertilized by sperm from a slightly different species of coral. This process, called hybridization, allows for even more genetic combinations. Researchers think this is one explanation for the amazing variety of coral forms – a diversity that makes coral reefs some of the most amazing places in the ocean.