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					       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:
   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?)
   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.
   CONTINUITY: the northern section of the reef is older
    (15 million years) and in the south younger (2million).
              Key Words
 Zooxanthellae   – 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.
   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
   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:
   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
   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:
 Coralreefs 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.
   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:
   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

				
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