Hwa Chong Institution (High School Section)
Humanities Department
Geography
Coast Worksheet 5: Coral Ecosystem
Name: ____________________ ( ) Date: ________ Class : Sec 3 __
1.
Watch the video
http://video.nationalgeographic.com/video/environment/habitats-environment/habitatsoceans-env/coral-reefs/
2..
With information from the video, as well as your text, complete the graphic organizer below
to get a sound understanding of corals. (You could use mind42 or other online tools too)
What?
Structures at or slightly below sea level, on the seabed.
Describe corals
How do
corals form?
Where are
corals found?
(state global
distribution)
Why found
here? (state the
ideal conditions
for corals)
Polyps secrete calcium carbonate around themselves for protection.
When they die, their limestone shell sinks to the bottom. Subsequent
generations of polyps build upon these skeletons.



Widely distributed in the world
Mostly between the tropics
S E Asia has the largest concentration and biodiversity of coral
reefs
These areas have ideal conditions for coral growth:
a) Warm sea temperature of 17 – 18  C
b) Depths of 10 to 60 m to allow sunlight to penetrate to allow algae
photosynthesis
c) Average salinity
d) Strong wave action to increase food and oxygen supply, and
prevent sedimentation from suffocating corals
Value /
usefulness of
corals
a) They allow a wide range of marine creatures to breed and grow.
They support 25% of earth’s marine species (provisioning services)
b) Protect from wave erosion, as they absorb wave energy. However,
during severe storms, they can get damaged (regulating services)
c) They are tourist attractions, contributing to the revenue in many
areas, eg Maldives (cultural services)
d) Jewellery and ornaments made from corals are in demand, which
contribute to the countries tourist dollars. But in recent years, “Look,
No Touch” approach is gaining acceptance as locals and tourists
understand the fragile nature of coral ecosytems (provisioning
services)
Pressures on
coral
ecosystems
Natural:
o Floods
‐ during floods in Australia, chemicals from farms, trace metals
from flooded mines, top soil, rubbish, etc get washed into
rivers and enter the sea
‐ these suffocate the coral reefs, and reduce salinity of the
water, causing damage to the Great Barrier Reef
Man-made:
a) Overcollecting – overfishing in reefs and surrounding coastal
areas. This affects the fragile balance of the food chain, eg at
Philippines
b) Fishing methods
‐ use of dynamite in Philippines and Indonesia destroy coral
habitats
‐ spear fishing of selected fish upsets the food chain balance,
eg in Belize Bonaire, the Neatherlands
c) Tourism / recreational activities
‐ result in more waste being discharged into the sea, affecting
coral growth
‐ building of harbours, use of more boats damages corals
d) Pollution
‐ Chemicals from farms, factories and sewage causes sea
water to turn murky, preventing sunlight from reaching coral
polyps. This reduces their food production ability.
e) Siltation
‐ As forests are cleared, more sediments are washed into the
sea, causing water to turn murky, preventing sunlight from
reaching coral polyps.
f) Climate change.
‐ As global temperatures rise, sea temperatures increase too
‐ Sea levels rise too
‐ These changes are faster than the rate at which the
ecosystems can adapt
‐ Result in coral bleaching – ie algae die, causing corals to
turn white, eg at Seychelles
3. Should governments take steps to protect coral reefs? Give reasons to support your
answer.
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