Corals are residents of the ocean floor at a wide range of depths and locations.
Similar to the way in which the armored and sedentary barnacle is basically a crab that decided to stick in place and collect food from the ocean around it, corals are actually colonies of small organisms similar to a jellyfish or sea anemone.
Instead of embarking on risky and energy-intensive swims through the world, corals have evolved ways to link together and create large, complex structures using groups of small individuals (similar to the Power Rangers). Some corals live deep in the ocean among the caves and crannies of the sea floor, using stinging tentacles to catch and kill small food items that pass nearby.
Coral reefs are what first come to mind when the word coral is thrown around, however. These huge congregations of hard, stony corals are always in warm, clear, shallow water. This is because while the corals that grow in coral reefs have stinging tentacles that they use at even the slightest inclination of nearby danger or food, they have also developed symbiotic relationships with photosynthetic algae that they rely on for a large amount of their nutrient requirements.
Reef corals give these microscopic powerhouses a place to live and some nutrients in return for byproducts from the photosynthesis that the algae perform.
Because of the huge success of this relationship, reef corals are able to grow very fast compared to other corals, and at the same time they reinforce their positions with large amounts of calcium carbonate that they leech from the surrounding environment. After each coral individual dies, a new polyp develops on top of this mineral deposit, eventually building up and creating the large shapes that make up coral reefs.
It should come as no surprise to the reader that coral reefs are some of the most biologically active and diverse ocean habitats. Due to their ability to feed a large amount of organisms while also sheltering them from the effects of harsh storms, coral reefs are generally regarded as the rainforests of the sea.
Like oases in a vast oceanic desert, reefs are home to a huge amount of organisms at various points in their lives. Among the frenzied activities of the various fish, crustaceans, birds and other creatures living in and around reefs, the corals themselves are also constantly engaged in pitched territorial battles with their neighbors. As they compete for limited space in order to give their algae the best spot for photosynthesis, corals sting and sometimes even attempt to digest coral intruders by turning their stomachs inside out and hitting or enveloping their targets.
Coral reefs have generated recent media attention due to the fact that large amounts of these important ocean environments have developed a condition known as bleaching. This is when the vibrant colors usually found among the corals are replaced with stark, bony white. Most of the colors of reef corals are actually from the different algae that are residing within their cells.
Bleaching is believed to occur when the surrounding environment is unfavorable due to high temperatures and/or pollution. These build up to the point that the algae are unable to generate energy from sunlight efficiently, and are ejected from the coral in a last ditch effort by the corals to preserve their energy.
While many times they are unable to recover from a long-term loss of their algae coworkers, some scientists believe that corals rely on bleaching in order to purge themselves of algae weak to certain environmental conditions while at the same time hopefully picking up other, tougher types.
Brannen Basham and his wife, Jill Jacobs, operate Spriggly’s Beescaping, a business dedicated to the preservation of pollinators. He can be reached at email@example.com.