10D – Slide 1
Topic 10D:
Coral Reefs
Online Lecture:
Coral Reefs
○ Coral Polyps & Zooxanthellae
○ Coral Bleaching
○ Coral Reef Development
○ Benefits/Uses of Coral Reefs
Pictures of Coral Reefs
10D – Slide 2
Why isn’t life abundant in
most parts of the tropics?
Why is life so abundant
in coral reefs?
Pictures of
Coral Polyps
Partnership between coral polyps 10D – Slide 3
and algae called “zooxanthellae”
Don’t
Touch!
Coral polyps eat plankton, and give the nutrients
in the plankton’s bodies to their zooxanthellae:
● Corals make sure nutrients are used for their benefit
(nutrients are not excreted [“thrown away”]).
● Nutrients (in plankton’s bodies) enter the reef,
but do not leave. (Corals are “concentrating” them.)
● When corals die, nutrients enter the local ecosystem.
Sunlight & Coral Growth
10D – Slide 4
Add a little more calcium carbonate
beneath them each year…
one year's growth
Need a hard, solid bottom to grow on
(sediments like sand or mud are bad – Why?)
Pictures of Reefs
10D – Slide 5
Bleached Coral
10D – Slide 6
10D – Slide 7
Corals Do Not Like
Nutrient-Rich Water
Light
algae grow really fast,
much faster than corals
How does this
harm the corals?
seaweed
Coral Reef
Life on a Coral Reef I
10D – Slide 8
Seaweed
(Algae)
Algae is always
present on a reef
Life on a Coral Reef II
10D – Slide 9
Most animals eat
algae, not corals!
Animals protect the
coral from the algae
Kinds of Coral Reefs
Fringing
Barrier
10D – Slide 10
Atoll
10D – Slide 11
Coral
Reproduction
Gametes (eggs & sperm)
meet in the water.
Plankton drift until
they die or find a
good spot to live.
Add a little more calcium carbonate
beneath them each year…
one year's growth
Reproduce (“clone”):
brothers/sisters on either side.
Coral Reef Development
10D – Slide 12
Corals
Grow
Upward
Fringing
Reef
Barrier
Reef
Atoll
Progression first
explained by
Charles Darwin.
Coral Benefits I
10D – Slide 13
Tourism
$400+ billion per year
in fish and tourism…
protect shorelines/beaches
from erosion by waves
protect from tsunami
Fish =
Food
Coral Benefits II
10D – Slide 14
medicines from “bioprospecting”:
in use or testing: drugs that fight cancers,
arthritis, poison oak, sunscreens,…
record information about
climate in the past
The preferred source for
temperature data for the
last few 10,000’s of years.
huge biodiversity:
25% of fish species live
in coral communities!
Chemical attacks & defenses are
common among reef organisms.
“Coring” Coral
one year's growth