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

Bleaching Coral

Prebleach

Postbleach

Primary Producers of Coral Reef

• Do photosynthesis to make food that feeds all other life- autotrophs

Primary producers: 1. zooxanthellae 2. turf algae

3. Bacteria4. 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