Great Barrier Reef

REEF FACTS AND FIGURES
The Great Barrier Reef Marine Park was established in 1975, and it is the world
largest marine protected area in the world.  It is approximately 348,700 square
kilometres in area and approximately 2,300 kilometres long, running from just
north of Bundaberg to the tip of the Cape York Peninsula.

The reef contains over 2,900 reefs which includes 760 fringing reefs, and 300
coral cays. There are also 618 continental islands, which were once part of the
mainland.

As the world's largest coral reef ecosystem the Great Barrier Reef is home to
approximately:-

  • 1,500 species of fish
  • 400 species of corals
  • 4,000 species of molluscs
  • 500 species of seaweed
  • 215 species of birds
  • 16 species of sea snake
  • 6 species of sea turtle


and some of the largest populations of dugong in the world.
 
ARE WE GOING TO SEE ANY SHARKS?
If you see a shark while visiting the reef, consider yourself very lucky as
sharks are not frequently encountered by visitors.  Of those which are seen
the most commonly encountered are the white tip reef and black tip reef sharks.
Easily identified by the white markings on the tips of the dorsal fins, they
are often found resting upon the sea floor.  Like most sharks white tip's are
extremely timid and won't stay long around divers.
Most sharks found on the reef are fish eaters and therefore pose no threat
to visitors.  
Do not harass or block off a shark's exit as they may attack out of fear.

WHAT ABOUT STINGERS?
The box jellyfish is found in the coastal waters of North Queensland during
summer months (October to March).  Visitors wishing to swim during this period
should only do so in protective swimming enclosures or wear protective clothing.
The box jellyfish is a coastal species and is not found out on the reef, but
they can sometimes be found around islands close to the mainland.
Other stingers that are sometimes encountered on the reef include the irukandji and blue bottle.  Both can cause a nasty sting, Vinegar can used on both box jellyfish and irukandji stings but not on blue bottle stings.  For blue bottles use cold water and ice.

WHAT FISH IS THAT?
With over 1500 species of fish on the reef the answer to this question is not
an easy one.  The use of identification books and underwater cards can be useful in identifying commonly encountered species.  Body and mouth shape are often the best key features in identifying the type of fish.  The reef fish section of the marine biology manual will outline the features of the most commonly encoungered families of fish.  Aim to learn the name of just one fish every time you visit the reef, and you will quickly know the most commonly encountered
species.

WHY ISN'T CORAL VERY COLOURFUL?
Most visitors to the reef comment that the coral isn't very colourful as they
are used to seeing brightly coloured images in books and on television.  
Natural white light is made up of all the colours of the rainbow; underwater,
these colours are filtered at different depths with red and yellow disappearing
first.  This gives the reef a predominantly blue/green appearance.  Photographs and video are taken using lights to show the true colours of the reef.  So the colours are there, it's just that you need white light to see them.  This is why night diving on the reef is so spectacular.

WHAT ARE CORALS?
Coral are made up of a thin layer of living animals called polyps, which secrete
a chalky, limestone skeleton as they grow.  Coral colonies grow as the polyps
divide and multiply in a process known as budding.
In addition to catching planktonic prey with their tentacles corals also derive
nourishment from simple single celled algae called zooxanthellae (pronounced
zoo-zan-thelly). living within their tissues.  Like all plants, zooxanthellae
photosynthesize, producing nutrients from the suns energy which are used by the polyp for its own nutrition.  Corals with zooxanthellae are able to lay down
limestone skeletons up to three times fster than those corals without.

WHAT TYPE OF CORAL IS THAT?
Trying to identify particular species of coral is very difficult.  What makes
it so difficult is that one type of coral may appear as a branching form in
calm water and look like a plate coral in another area.  In many cases it is the
environmental conditions, such as wave action, light levels and the amount of
sediment in the water, that influence coral colony shape.

The easiest way to identify corals is by their appearance

  • boulder
  • branching
  • plate
  • table
  • vase
  • bushy
  • solitary

WHAT ABOUT CORAL SPAWNING?
Every year over one third of the reef's 350 species of coral reproduce sexually
during a mass spawning event.  The majority of inner reefs spawn around November with the outer reefs spawning later in December.  Spawning always takes place at night, and follows any time up to six days after the full moon.  Eggs and sperm are released into the water where they eventually combine to form a free swimming planktonic larval stage.

WHY IS THE REEF SO FAR OFFSHORE?
Most of the Great Barrier Reef is located off the mainland of Queensland.  
Corals need clear water which are low in nutrients.  They cannot not tolerate
freshwater or nutrients carried in the water run-off from the mainland.  
That is why the most diverse and abundant corals grow offshore where the
environmental conditions are more suitable.

WHAT IS THE WATER CLARITY GOING TO BE LIKE?
The clarity of water on the reef is determined by a combination of the amount
of sediment and the amount of phytoplankton in the water.  Sediment becomes
suspended due to increased water motion caused by tide changes, high winds and storms.
Phytoplankton are the microscopic plants that drift around in the water.  They
are more numerous in areas where the nutrient levels of the water are higher
particularly around coastal reefs which receive nutrient rich runoff from the land.

ARE WE GOING TO SEE ANY WHALES?
Whales are normally encountered during the winter months when they migrate up to the reef from Antarctic waters to mate and give birth.  One of the most spectacular visitors during this period is the Humpback.  They are seen in theshallow coastal waters of the Great Barrier Reef ranging from Harvey Bay to Port Douglas.  Whale watching is conducted by a number of tourist operators through these areas.The Minke is another species of whale seen during winter, particularly around the Ribbon Reef area.The smallest whales, the dolphins can be seen all year round in most parts of the reef.

WHAT ABOUT CROWN-OF-THORNS STARFISH?
The cause of Crown of Thorn Starfish outbreaks is still the focus of a lot of research and debate.  Increased nutrients from the mainland and effects due to El Nino are all being investigated as is the possibility that it is a naturally occurring event.  Crown of Thorns starfish may actually serve to maintain coraldiversity on the reef by feeding on the fast growing species, that if left unchecked, could dominate the reef.

WHERE CAN WE GO FISHING ON THE REEF?
Fishing is not allowed in green national park zones or pink preservation and orange scientific zones. In other zones fishing is allowed subject to Queenslandfisheries restrictions.  Legal sizes, closed seasons and catch quotas also apply.