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CORAL REEFS
Secondary Sources (Evidence) used:
• Dr.Tim Flannery – We are the Weather Makers (2007 Australian of
the Year and Scientist at Macquarie Uni)
•Sydney Aquarium
•Stacey and Lucas – Investigating Geography
•GBRMPA
•Paine – Macquarie Revision Guides
Spatial patterns and dimensions:
• Coral reefs are located in:
- shallow areas in tropical latitudes, or where warm ocean
currents flow in temperate areas
- a zone extending at most from 30°N to 30°S of the equator;
- reef-forming corals do not grow at depths of over 30 m so as
light can penetrate allowing the algae and
plankton to work together to photosynthesise in the coral
- warm waters where the water temperature falls below 16 °C
Large reef-building areas include:
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the Caribbean Sea,
the western Indian Ocean
the western reaches of the South Pacific.
Non-tropical coral reef zones of :
(a) the Red Sea, where heat from the surrounding desert
climate warms the ocean and
(b) Australia's Great Barrier Reef which is warmed by a
tropical Pacific Ocean current.
The Great Barrier Reef
• is the largest coral reef system in the world
• It is not one continuous reef but a series of reefs
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of roughly 3,000 individual reefs and 900 islands
that stretch for 2,600 kilometres and cover an
area of approximately 344,400 km².
The reef is located off the coast of Queensland
in northeast Australia from……
 Worldwide coral reefs are estimated to cover 284,000 sq
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km
the Indo-Pacific region has 92% - of this South East Asia
accounts for 33% and Australia 41%;
the Atlantic and Caribbean coral reefs only account for
7.6% of the world total
Coral reefs are either restricted or absent from along the
west coast of the Americas, and the west coast of Africa
due to cold ocean currents that reduce water
temperatures.
Corals are also absent from from Pakistan to Bangladesh
and the coast around north-eastern South America and
Bangladesh due to the release of vast quantities of
freshwater from the Amazon and Ganges Rivers
• Coral reefs one of most biodiverse
ecosystems in the world
• although they are located in nutrient-poor
tropical waters the process of nutrient
cycling between corals, zooxanthellae, and
other reef organisms provides an
explanation for why coral reefs flourish as
the recycling ensures that fewer nutrients
are needed overall to support the
community
Biophysical interactions:
* weather and climate
* geomorphic and hydrologic processes
* weathering, erosion, transportation, deposition
* invasion, succession, modification, resilience
* adjustments and responses to natural stress
* food webs, food chains.
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Producers
Producers are the base of the food chain and are very important because all of the energy in the
community flows from them. On coral reefs there are three major types of producers:
Cyanobactera or blue-green algae
These species also fix nitrogen and enhance nutrient availability
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Seaweeds
These include both conspicuous macro-algae and the less conspicuous but very abundant turf algae.
Seaweeds are heavily grazed by herbivores
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Reef-building or hematypic corals
Corals are producers due to tiny plants that live inside their bodies called zooxanthellae
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Benefits of Zooxanthellae to coral
Benefits of coral to zooxanthellae
removes coral waste
provides nutrients to the coral
accelerates coral skeleton growth
provides safe place to live
lets sunlight through to zooxanthellae
provides abundant nutrients from waste
Thus, corals are producers because the zooxanthellae provide nutrients via photosynthesis to the
corals. As a result, many corals live entirely off of sunlight.
Natural stresses on the GREAT
BARRIER REEF
• Cyclones – breaks off coral, changes salinity of the water column,
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turns over the water column to lessen warm water in upper layer
and reduces global warming threat
Marine organisms – burrowing, boring and breaking
Predators - Crown of Thorns Star Fish – native top predator kills the
coral– dependant on currents and water temperature for larvae to
spread
Sea Level change – 15,000 years ago sea level was lower forcing
corals to die and re-colonise new areas
Flooding and runoff from mainland – can affect salinity levels and
carry sediment into the reef system
Subsidence and continental drift has affected where corals colonise
over the last 15 million years
Value of Coral Reefs:
• Coral reefs yield around US$30 billion in
income each year mostly to people in
developing nations
• One in four organisms in the ocean spends
part of its life in coral reefs
Human Impacts - Threats to Coral
Reefs:
1. GLOBALLY
• Coral Bleaching episodes due to climate change
• Sea level change due to global warming occurring around Pacific
Islands will affect depth of coral growth
• Over fishing including dynamite fishing and cyanide fishing in
poorer countries and illegal fishing of endangered species
• Algal Blooms from nutrient runoff
• Fisheries – trawling; aquaculture – nutrient waste;
• Tourism – anchor damage, litter, touching, souvenirs, sewage from
resorts and boats, hand feeding changes feeding habits,
development on islands, moorings,
• Shipping – oil spills, sewage, litter, anti fouling agents on hulls
• Agriculture and logging activities creating increased silt and
nutrient runoff particular problems in South East Asia
• Introduced species
2. GREAT BARRIER REEF THREATS
• Crown of Thorn Starfish damage due to food chain disturbance –
increased nutrient runoff and warming oceans allowing more larvae
to survive
• Road building - in 1982 controversy over unsealed road built in
Daintree rainforest Qld caused silt runoff onto coral reef/one of only
two places in the world where coral reefs live next to rainforest –
caused political issue/campaigns and ultimate protection of Daintree
as World Heritage Wet Tropical Rainforest Area
• Acidification of the water and increasing brittleness of coral due to
warming oceans
• Extinctions and threats to endangered species eg. Green turtle
protected – once processed into soup;
• Tourism
• Runoff of silt and nutrients from fertilizers from farms
• Global Warming
The Great Barrier Reef and climate
change:
• Is the most vulnerable reef in the world to climate
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change
42% was bleached in 1988
18% suffered permanent damage
2002 90% all inshore corals killed by ocean warming
2006 coral bleaching avoided due to Cyclone Larry which
mixed the warm top layers of the ocean with the cooler
water below (water column mixed) however 50,000
homes in Queensland destroyed, crops wiped out and
people killed.
Coral Reefs in the future:
• Coral reef scientists warn that :
 1°C rise in global temperature will cause
82% of GBR to bleach and die
2°C rise in temperature will bleach 97%
reefs
3°C rise will cause total devastation
Traditional and Contemporary
Management Strategies: