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