coral reefs
EMULATE
While they make up less than 1% of the ocean floor,
the world’s coral reefs contain upwards of 25% of all marine life, which, through a complex web of relationships thrive in an impressively challenging ecotone, marked by wave energy, massive storm disturbance, temperature changes and UV exposure. There are three main coral reef typologies: fringing, barrier and atoll. While the conditions that give rise to these typologies differ, all reefs share some similarities in the condition in which they grow, including bottom topography, wave and current strength, light, temperature and suspended sediments. Coral itself comprises the living substrate upon which reef colonies develop. A single coral polyp, the result of sexual reproduction, reproduces asexually to create a coral body made up of thousands to millions identical polyps that share a nervous system and some digestive functioning. Each polyp secretes calcium carbonate (the genesis of limestone) and lives within the resulting cup shape, or calyx. Periodically, the polyp will secrete a new calyx floor, resulting in slow growth (.3 – 10 centimeters per year). Inside its custom calyx, a polyp remains safely ensconced in the daytime. At nighttime, however, the polyp will emerge from the calyx to feed on the currents. In addition to these nighttime current feedings, coral and algae have formed an obliged symbiosis; polyp tissue contains photosynthetic algae that aids in coral’s growth. Coral, in exchange, protects the algae while providing it with compounds it needs for photosynthesis. In some species of coral, this symbiosis is so specialized that the coral body has the ability to filter UV light to maintain ideal conditions for the algae’s photosynthesis. This foundational relationship between coral and algae is just the first example of symbiosis in an ecosystem marked by cooperation. Coral is half of the symbiotic pair in many different relationships, providing habitat and protection to crabs, lobster and shrimp, which in return provide protection against aquatic worms and other predators that would feast on the softbodied polyps housed in the coral. Clown fish and anemones live in close symbiosis; the fish supply the anemone with food, the anemone protect the fish, which have a special immunity to the anemone’s sting. Moray eels and coral trout, two entirely distinct fish species, hunt in pairs and equitably split their catch. A variety of cleaner fish eat parasites off larger fish – an exchange that feeds the former and keeps the latter healthy.
WRITTEN BY EDITORIAL STAFF IN CONSULTATION WITH JUAN ROVALO OF BIOHABITATS 52
