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Learn how sediment clouds, salinity variations, and pollution affect coral reefs. Explore the role of primary producers like zooxanthellae and ways coral compete and face predation in their ecosystem.
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Sediments, salinity and pollution • Fine sediment clouds H2O smothers coral • Cuts down light for zooxanthellae • Coral mucus can clean H2O (limited amount)
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
Sediments, Salinity and Pollution • Coral bleaching expels zooxanthellae
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
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
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
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
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