Transcript coral reefs - bankstowntafehsc

CORAL REEFS
References:
 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 – web site
Paine – Macquarie Revision Guides
Professor Ove Hoegh Guildberg, University of Queensland.
Coral
Reef
Ecosystem
Coral Reefs are found where the
following biophysical conditions exist:
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Coral reefs occur where:
- shallow areas in tropical latitudes, or where warm ocean
currents flow in temperate areas
- a zone extending from Latitudes 30°N to 30°S of the equator;
- water depths from 2 to 30m because they need light to allow
the algae (zooxanthellae) to photosynthesise in the coral
- warm waters where the water temperature does not fall below
17°C nor exceeds 34˚S with the optimum temperature being
26-27˚ for coral growth.
- where waters are clear and free of nutrients otherwise algae
and slime will cover the coral and stop it photosynthesising
- constant levels of high salinity
- high oxygen levels where wave activity continually oxygenates
the water
- low sediment levels as this will smother the coral and stop
photosynthesis
Global locations of large
reef-building areas:
- 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.
Location of Coral Reefs Globally
The Great Barrier Reef
– Spatial Pattern (where is it?)
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LOCATION: off the coast of Queensland in northeast
Australia from Latitude 8˚S to Latitude 24˚S stretching
from Papua New Guinea to Fraser Island. The World
Heritage area extends from Cape York to just north of
Bundaberg
 SIZE: is the largest coral reef system in the world but is
not one continuous reef but a series of 2,900 individual
reefs and 600 islands that stretch for 2,300 kilometres
and covers an area of approximately 348,700 km².
 SHAPE: it has four distinct regions Northern, Central,
Mackay and Southern ranging from the continental shelf
to coral cays and islands.
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CONTINUITY: the northern section of the reef is older
(15 million years) and in the south younger (2million).
Key Words
– microscopic algae that
live inside the coral polyp
 Symbiotic relationship – where two
organisms benefit without damaging either
organism
 Spatial – where it is found?
location or distribution.
 Zooxanthellae
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GLOBAL SPATIAL PATTERNS:
 Worldwide coral reefs are estimated to cover 284,000 sq
km
 the largest area is in the Indo-Pacific region with 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 are one of most biodiverse
ecosystems in the world
 although located in nutrient-poor tropical
waters the process of nutrient cycling
between corals, the zooxanthellae, and
other reef organisms explains why coral
reefs flourish as the recycling ensures that
fewer nutrients are needed overall to
support the community
The GBR has the richest fauna
biodiversity on the planet
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Over 2000 fish species
500 coral species
300 hard coral species
Over 400 sponge species
4000 molluscs species
23 species of marine mammals
11 species sea snakes
6 species of turtles
215 species of birds
Migrating whales
Conditions necessary for Coral
Reefs to grow:
Corals are animals related to jellyfish. They have
microscopic algae called zooanthellae which
photosynthesise living inside their tissues in a symbiotic
relationship. Therefore, Corals need the following:
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Shallow water 2 to 30 metres so photosynthesis can occur
Warm ocean temperatures 20-35˚C (ideally 26 to 27˚C) to build
limestone
Clear water low in nutrients. Nutrients such as phosphates and
nitrogen increase algae growth and will smother corals.
Constant high salinity
High oxygen levels where wave action oxygenates the water
Low sediment levels as silt will smother the algae and stop
photosynthesis occurring.
Natural stresses on the GREAT
BARRIER REEF
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Cyclones – breaks off coral, changes salinity of the water column,
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
Threats to Coral Reefs:
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
 Acidification of the oceans due to increasing CO2 which when
dissolved lowers pH and weakens carbonate ions in coral and
shellfish.
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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 causing 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:
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Is the most vulnerable reef in the world to climate
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
Latest News
Cargo ship's oil
spill threatens
wildlife 12/3/09
A cocktail of 650 tonnes of fuel
and fertiliser has been lost from
a cargo ship caught in fierce
seas from cyclone Hamish off
the south-east Queensland
coast, potentially threatening
wildlife
Location of
Great Barrier
Reef