What type of coral is in the great barrier reef

They fight back by producing chemicals in their tissues that make them distasteful or even poisonous to those animals.

Soft corals also have spiky spicules which function like thorns on a rose bush. Colonies of boulder coral — which can live up to one thousand years — are likely to be the longest living corals on the Great Barrier Reef.

These corals grow in height at about one centimetre each year. Some branching coral species, such as staghorn corals, can grow up to 30 centimetres each year, while the porites stony corals with finger-like structures grow at an annual average of one to three millimetres. Soft corals grow relatively quickly and may double or triple the size of their colonies over a year.

Some corals have pigments fluorescent proteins in their tissues that give them their orange, yellow, green, blue, red and purple colours. Others get their golden-brown colour from the algae, called zooxanthallae, that live within their tissues.

Most of their nutrients come from the zooxanthellae. Like plants, zooxanthellae use the sun to make food for themselves and the coral. This is why it is important for corals to live in clear, shallow waters where they can get lots of sunlight.

Corals also eat plankton — these are tiny animals or plants which drift around in the water. Some corals also consume very small fish.

Heterotrophic taxa are easily visually distinguished from their phototrophic relatives by their bright yellow, orange, red, pink, purple or snow-white colouration Fig. As sessile organisms without a protective skeleton, octocorals would appear to be vulnerable to predation. However with the exception of a few snails e.

Many species are protected against predation, fouling by algae or overgrowth by neighbouring organisms through feeding-deterrent, toxic or allelopathic secondary metabolites. Many of these substances have been investigated for their bioactivity, and some may one day become pharmaceutically relevant. Octocoral colonies, although not contributing to reef growth, nevertheless provide shelter to a range of other reef inhabiting organisms. For example, some species of brittle star Ophiuroidae , feather star Crinoidea , shrimps, ctenophores and fish gobies and pygmy sea horses are exclusively found living on the surface of specific octocoral colonies.

Most of these associates use the octocoral colony exclusively as perch or for shelter; however a few of these associates appear to also feed on the mucus of the octocorals. After hard corals, octocorals are the second-most common group of macrobenthic animals on the GBR. Octocorals are highly diverse not only taxonomically but also ecologically, including species with widely contrasting ecological niches and life history strategies.

Richness increases from south to north Fig. Outer-shelf reefs contain diverse octocoral communities that are often characterised by high abundances of members of the family Xeniidae. Deep-water reef slopes and inter-reefal habitats are inhabited by azooxanthellate taxa such as many gorgonians and Dendronephthya , as well as ubiquitous and tolerant taxa such as Sinularia and Sarcophyton.

Inshore reefs with fluctuating salinity and water clarity contain some species that are rarely found in clear-water habitats e. Many of the Xeniidae and Nephtheidae are missing on turbid inshore reefs. Ecological surveys have shown that the taxonomic richness of octocorals also increases from shallow water to moderate depths. It is further related to water clarity and amounts of sediments deposited.

Changes in taxonomic richness and community composition in octocorals have therefore been suggested to be suitable as indicators of past and recent disturbance by poor water quality on the Great Barrier Reef and other reef environments.

Australian Institute of Marine Science, Townsville. ISBN: 0 The Great Barrier Reef, like most other coral reefs on earth grew from a hard surface on the ocean floor and continually evolved over the course of , years to take the shape of the vibrant ecosystem that can be found in today. The corals have pigment in their tissue which them give their colourful hues. Hard corals are found in clear, shallow tropical waters and has contributed to the relatively swift growth of the Great Barrier Reef.

Soft corals are an essential food source in the entire Great Barrier Reef -as marine algae- in which the entire ecosystem is dependent on.