Transcript Coral Reefs
Sediments, salinity and pollution • Fine sediment clouds H2O smothers coral • Cuts down light for zooxanthellae • Coral mucus can clean H2O (limited amount) sediments Sediments, Salinity, and Pollution • Mining, logging, construction, dredging, increase sediments in H2O Sediments, Salinity and Pollution • Pesticides, industrial wastes, agricultural wastes, and fertilizers increase algae which blocks light from zooxanthellae = eutrophication Water pollution Eutrophication algal bloom Satelite image of an algal bloom Sediments, Salinity and Pollution • Coral bleaching expels zooxanthellae Bleaching Coral Bleaching Coral Bleaching Coral Prebleach Postbleach Bleaching Coral Primary Producers of Coral Reef • Do photosynthesis to make food that feeds all other life- autotrophs Primary producers: 1. zooxanthellae 2. turf algae 3. Bacteria 4. coralline algae Turf algae Turf algae Cyanobacteria/bluegreen algae Coralline Algae Coralline Algae Hard Coral: competition • Fast growers grow up and spread out to catch light and block others • Attack other organisms with mesenterial filaments-digest them • “Sweeper tentacles” with nematocysts sting neighbors Plate Coral Plate Coral Coral stinging each other Soft coral competition • Soft corals-have sharp needle spicules to discourage predation • Can also move around some, slowly • Contain toxic (bad tasting) chemicals released into H2O can kill hard coral Soft Coral Soft Coral Soft Coral Two hypotheses about competition • Lottery hypothesis= feeding habits /life styles overlap and competition is strong. Survival is luck • Deterministic hypothesis= each organism has its own niche. Most accepted Definitions • Ecological niche= what a species eats where it lives, how it behaves and all other aspects of its lifestyle. “job” or role in a community • Competitive exclusion= one species out competes the other. No two species can occupy the same niche Predation on corals In what way is coral predation like plant grazing by herbivores? “predators” graze down the coral without killing it off entirely. The affect predation has on the number and type of coral • Fast growing corals are held in check by predation (butterfly-fish,coral-eating snails) • Crown-of-thorns sea star eats only certain corals Herbivores/grazers on the reef • • • • • • Parrot fish Damsel fish Sea urchins Surgeon fish Snails Crustaceans Parrot Fish “Grazing” Fish What if the herbivores/ grazers were removed? Grazers control algae growth algae overgrows reef, kills coral If pollution is added (nutrients) algae grows explosively = eutrophication chokes out everything See eutrophication