BIOLOGY OF CORAL REEFS Chaper 1 Objectives Introduction to the Biology of Coral Reefs In what ways are coral reefs extreme Large enough to be seen from space Largest structures ever built by living organisms Biological diversity is greater than any other marine system types of species and number of organisms Complexity of interactions among organisms is extreme each species plays its own role many inter dependencies between species Extreme vulnerability to abuse from humans How are coral reefs important to humans Protect coastlines from waves Hurricane and storm waves lose their destructive power as they break on reef Home to fish shellfish corals shells pearls decorative materials Provides Calcium Carbonate for medical uses and other pharmaceutically useful chemicals Coral limestone and mounds of sand used as building materials Attracts tourism What are the environmental requirements of corals and how do they constrain the geographic distribution of reefs built by corals Thrive in clear tropic waters Temperatures above 20 degrees C subtropical and tropical seas Sunlight is required only found in water shallow enough for light to penetrate or water clear enough for light to penetrate as deep as 50 meters Generally constrained from 25 degrees North and 25 degrees South Warm surface currents flowing northward extend the geographic distribution farther than 25 degrees North in the case of Bermuda and Japan Cold currents flowing toward the equator constrain reefs to a narrower latitudinal range Salinity must be near the seawater average 35 parts per thousand Outflows of large rivers carry sediment loads that dilute seawater to the point that coral reefs cannot exist near river mouths Vigorous water movement is beneficial ensures water is well oxygenated unless too vigorous ex a heavy storm Coral reefs grow on about one third of tropical coasts Why can corals be considered part animal part plant and part rock Are animals same group as sea anemones hydras and jellyfish Cnidarians Cnidarian Sac like design mouth opening into a gut called the gastrovascular cavity Create initial architecture of a reef by producing hard skeletons Build skeletons from calcium carbonate Zooxanthellae single celled microscopic plants live within coral tissue What other animals are closely related to corals and what are the characteristics they share Same group as sea anemones hydras and jellyfish Cnidarians Cnidarians Sac like design mouth opening mouth ringed with stinging cells nematocysts What are two ways in which reef building corals acquire food and what is the relative importance of each of these food acquisition mechanisms to corals Use tentacles to capture plankton Zooxanthellae which are plants in coral tissue produce their own food which leaks to corals producing most of their food How does living as a colony influence patterns of growth and possibilities for overall shape As the surface area of the colony increases more polyps are required to cover it Small polyps are added by budding between larger polyps as the colony s surface area increases What are the stages of the coral life cycle both sexual and asexual Asexual Growth by budding of polyps to produce more polyps Asexual After being broken by physical disturbances old fragments of the colony can reattach and continue to live as physiologically independent colonies Sexual Some coral species are hermaphrodites producing both eggs and sperm Sexual Some coral species release sperm which fertilizes eggs Sexual Some coral species release eggs and sperm simultaneously called Spawning Sexual stages Fertilization of eggs sets in motion a sequence that results in simple elongated balls of cells called planula larvae The outside of the larva has tiny hairlike structures called cilia that propel it through the water for a few hours days or even months whatever it takes to reach the stage of readiness to settle to the bottom and begin the formation of a new coral colony After years of growth the coral life cycle is continued to the next generation when the coral becomes large enough to produce gametes of its own
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