GBR Case Study dab pj

The Great Barrier Reef is a large coral reef off the coast of North-East Australia. The reef itself is larger than some countries including Japan and is the largest living thing on Earth, and is also one of the 7 ancient wonders of the world. The reef is home to an abundance of marine life and contains over 3000 different species of coral. However, the reef is being endangered through multiple different man made threats and if nothing is done, the reef may not be here in 30 years or less.


Ocean Acidification - The carbon dioxide that gets dissolved from the atmosphere forms carbonic acid. This means that the ocean becomes slightly less alkaline not acidic! (not enough acid in the world to make it acidic.) If the ocean is less alkaline corals become brittle and cannot form or get started.

Human Impacts - 93% of the reef has been destroyed and the other 7% will follow unless something is done. Over the years there have been multiple man made factors affecting the reef, including over fishing, run off, pollution, oil spillage, development. Until recently there has been nearly no effort at all to protect and replenish the reef.

If There Was a New Heron Island

Positive Impacts:

  • Can help find new species of fish, coral & maybe birds
  • Help conserve wild life in Great Barrier Reef
  • Reduce overfishing in that area

Negative Impacts

  • Could kill/destroy coral systems & the fish inside them
  • More pollution (rubbish, fumes & etc.)
  • Development of corals could fall since they get disturbed by people touching and taking piece of it

Coral Biology

Many corals resemble plants, they are close members of the animal phylum Cnidaria. Most corals are colonial, which means that each coral is made up of many individual polyps connected by living tissue (the coenosarc).


  • The skeleton of stony corals is selected by the lower portion of the polyp
  • This process produces a cup, or calyx, in which the polyp sits (corallite)
  • While the colony is alive, CaCo3 is deposited
  • Periodically, a polyp will lift off its base and secrete a new basal plate above the old one, creating a small chamber in the skeleton


Asexual Reproduction

  • Asexual reproduction results in polyps or colonies that are clones of each other – this can occur their budding or fragmentation
  • Budding is when a coral polyp reaches a certain size and divides, producing a generally identical new polyp. Corals do this throughout their lifetime
  • Sometime a part of their colony breaks off and forms a new colony. This is called fragmentation which can occur as a result of a disturbance such as a storm or being hit by fishing equipment.

Sexual Reproduction

  • In sexual reproduction, eggs are fertilised by sperm, usually from another colony, and develop into a free swimming larvae
  • There are two types of sexual reproduction in corals external and internal
  • Depending on the species and types of fertilisation, the larvae settles on a suitable substrate and becomes polyps after a few days or weeks, although some can settle within a few hours.

Broadcast Spawning

  • Most stony corals are broadcast spawners and fertilisation occurs outside the body (external fertilisation).
  • Colonies releases huge numbers of eggs and sperm that are often glues into bundles (one bundle per polyp) that float towards the surface.
  • Spawning often occurs once a year and in some places is synchronised for all individuals of the same species in an area.
  • This type of mass spawning usually occurs at night


Coral Diet

  • Carnivorous animals which capture prey with tentacles and nematocysts
  • zooxanthellae
  • Mucus Membrane
  • Trap organisms, cilia pass along the mouth
  • Transfer nutrients between polyp
  • Absorption through cell walls
  • DOM (Dissolve organic matter)
  • Zooxanthellae can also give 95% of nutrients

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