This document discusses coral reef and mangrove ecosystems. It describes how corals form structures through symbiosis with algae, providing each other with nutrients and oxygen. Coral reefs are found between 23.5 degrees north and south of the equator, and provide habitat and coastal protection. However, they face threats from coastal development, pollution, and climate change. Mangroves are salt-tolerant trees found in tropical coastlines, with adaptations like aerial roots and leaves that secrete salt. They stabilize coastlines and provide habitat, but around 20% have been lost since 1980 due to development and resource use. Both ecosystems face increasing threats from climate change, rising populations, and human activities.

1. 2016 Pure
Geography
T1 Wk5
Content Notes
“Coast”

2. CORAL REEF ECOSYSTEM – WHAT?
• Living structures found slightly below the
sea level on the seabed
• Polyps – animals that secrete calcium
carbonate to protect themselves
• Corals – the limestone skeleton of polyps
• Symbiosis – mutually beneficial
relationship between the polyps and
microscopic algae

3. CORAL REEF ECOSYSTEM – WHAT?
• Polyps – supply algae with nutrients and
carbon dioxide
• Algae – provide polyps with sugars and
oxygen
• The presence of algae also give corals
their distinctive colours
• When polyps die, their limestone
skeleton is left behind

4. CORAL REEF ECOSYSTEM – WHere?
Refer to fig. 1.54 on pg. 42
• Found mainly between 23.5o north and
south of the equator
• Tropic of Cancer and Tropic of Capricorn
• Pacific Ocean: South East Asia (about
70,000km2, North of Australia (Great
Barrier Reef)
• Indian Ocean: Maldives, Madagascar
• Atlantic Ocean: Caribbean islands

5. CORAL REEF ECOSYSTEM – Conditions
• High sea surface temperatures, 17 –
18oC
• Strong wave action to bring in food &
oxygen, and to wash away
sedimentation
• Average salinity
• Clear water, low level of turbidity
Why are these conditions necessary?

6. CORAL REEF ECOSYSTEM – value
• Habitat: breeding grounds for fishes,
shelter from predators, provide food for
large fishes
• Coastal protection: help to reduce wave
energy and impact of coastal erosion
• Recreation: coral reefs as prime diving
sites for tourism, build coastal resorts
• Resource: coral fragments can be made
into ornaments and jewellery

7. CORAL REEF ECOSYSTEM – pressures
• Coral reefs around the world face
constant pressure from human activities
and natural processes
• In SE Asia, about 95% of the reefs’
existence are under threat
• Pressures come mainly from coastal
developments, pollution and climate
change caused by human activities

8. CORAL REEF ECOSYSTEM – pressures
GROUP PRESENTATION
Topic: Pressures that threaten the
existence of coral reefs/mangroves
• Explanation of the “pressure”
• Examples of places where it is
happening
• Suggestions on solutions
• Each group will be assigned the topic
and type of pressure

9. MANGROVE ECOSYSTEM – What?
• Sub-species of tropical plants that are
salt-tolerant (HALOPHYTES)
• Found growing in tidal mud areas in
sheltered coasts
• Plants have mechanisms to survive high
salt content in water and waterlogged
soil that is low in oxygen
• Eg leaves that secrete excess salt, air
breathing roots

10. MANGROVE ECOSYSTEM – Where?
Refer to fig. 1.62 on pg. 48
• Found mainly between 23.5o north and
south of the equator
• Tropic of Cancer and Tropic of Capricorn
• Coastlines of tropical forests including
Borneo, Peninsula Malaysia, Brazil, New
Guinea and Madagascar

11. MANGROVE ECOSYSTEM – Adaptations
• Mangrove forest can be divided into
three horizontal zones, each with slightly
different adaptations
• Coastal zone – subject to regular tides
and submerging
• Trees here have pencil roots to breathe
oxygen from the air and for anchorage
• Eg Avicennia, Sonneratia

12. MANGROVE ECOSYSTEM – Adaptations
• Middle zone: submerged during high
tides, trees need prop roots to maintain
their height above the water
• Eg Rhizophora
• Inland zone: rarely submerged, trees use
knee-like roots to trap sediments for
plant growth
• Less tolerant of salt than other trees
• Eg Bruguiera
diagram

13. MANGROVE ECOSYSTEM – Adaptations
• Leaves: either secrete salt through
leaves, or accumulate salt in the older
leaves that are falling
• Fruits: either buoyant fruits that can
germinate in other coastal areas, or
javelin-shaped roots that pierce the mud
and can immediately germinate

14. MANGROVE ECOSYSTEM – value
• Stabilising shorelines by reducing wave
energy and impact of coastal erosion,
• Extend shorelines by accumulating
sediments
• Habitat and breeding ground for marine
animals, eg barnacles, oysters, shrimps,
crabs
• Resources: wood for charcoal and
building material

15. MANGROVE ECOSYSTEM – value
• Mangrove roots help to filter and
accumulate fine sediments and in the
process also improve water quality
• Recreation: locations for nature trails and
ecotourism
• UN Environment Programme report in
2006 estimated the annual economic
value of mangroves to be US $200,000
to $900,000 per km2

16. MANGROVE ECOSYSTEM – pressures
• Mangroves around the world face
constant pressure from human activities
and use of them as resources
• Since 1980, the world has lost about
20% of total mangrove area (about 3.6
million hectares)
• Pressures come mainly from coastal
developments, pollution and demand for
fuel wood and charcoal

17. THREATs to coastal areas
Threats to
coastal areas
Climate
change
Increase in sea
level
More extreme
weathers
Acidification
of oceans
Rising
population
Coastal
developments
Pollution