The Great Barrier Reef
QBIR
One of the seven natural wonders of the world
In an ecosystem, how do living things
depend on each other?
Do you think it is important to preserve
ecosystems? Why or why not?
Great Barrier Reef facts
The reef contains:
1,500 species of fish
 411 types of hard coral

 one-third of the world’s soft corals
 134 species of sharks and rays

 six of the world’s seven species of
threatened marine turtles

 more than 30 species of marine mammals,
including the vulnerable dugong.
The Crown of Thorns Starfish

The highest on the list of dangers to the
Great Barrier Reef lives on the reef itself. The
Crown of Thorns starfish feasts on the polyps
of coral, releasing neurotoxins to absorb the
tissue of the coral and literally “sucks the
life” out of the reef’s backbone.(the coral)
Once great numbers of Crown of Thorns
starfish are grouped together, their impact of
the reef can be catastrophic – if the number
of over 30 adult starfish reside in a 10 m.
area, it can be called an “outbreak” which is
usually a result of a lack of predators (such as
the Giant Triton) of the starfish within the
area. Many researchers believe that the
current abundance of Crown of Thorns
starfish could be a result of agricultural
runoff which increases the amount of algae
which serve as food for the starfish.
Photo © Sandra Pizarro
Question: How Do Coral Reefs Form?
Answer: Stony corals are a remarkable
group of animals that inhabit tropical
marine waters around the world and form
vast colonies known as coral reefs. Coral
reefs often resemble rock formations or
even plants but such resemblances are
only superficial. Coral reefs are in fact
made up of many tiny animals known as
coral polyps. Each coral polyp is an
individual animal and the individual
polyps coexist as part of a larger colony
of polyps.
Coral reefs provide habitat for an
immense diversity of other organisms
including fishes, marine mammals,
marine turtles, and invertebrates.
Stony corals inhabit marine habitats
where the water is quite clear, the
temperature remains within the range of
18°C-29°C
A stony coral colony begins as a single
free-swimming founder coral polyp that
attaches itself to a hard substrate such as
submerged rocks. The founder polyp
replicates itself repeatedly through
asexual reproduction, producing a colony.
The colony consists of a base which is
attached to the reef substrate, a growing
edge zone (where new coral polyps are
produced), and an upper surface that is
exposed to light that filters down through
the water.
Stony corals are named because of the
stone-like skeleton that forms within their
bodies. This hard skeleton is made up of
calcium carbonate (CaCO3) and gives a
coral reef much of its structure. Over
time, stony coral polyps lift up from their
base and new calcium carbonate is
deposited on top of the old surface. As a
result, the coral grows upward on a
mound of hard rock-like deposits.
Polyp
The beginning of coral growth
Dugong: related to the manatee. Currently endangered
in the area of the Great Barrier Reef.
Manatee: most commonly found in Florida