Hundreds of previously undocumented species have been found living in and around one of the world’s most visited coral reefs.

Bizarre and beautiful crustaceans, corals and colourful worms were discovered off the Australian coast by researchers working for the Census of Marine Life.

Many of the creatures had been seen repeatedly by scientists based in nearby research stations and by divers and professional guides on the Great Barrier Reef – but no one had realised their significance.

The species were identified during expeditions to the Ningaloo Reef off the northwest coast, and Lizard and Heron islands off the northeast coast, at opposite ends of the reef system.

Researchers said that the locations and quantity of previously unrecog-nised species picked up in the survey demonstrated just how little is known of the marine environment.

The survey concentrated on identifying little-known types of animals including isopods, soft corals and worms. Creatures such as fish, hard corals, sharks and sea slugs were ignored because their presence was well documented already.

“The impressive thing was the sheer number of the species sitting under our noses. These are places people have been diving on for years and they have research stations,” said Julian Caley, of the Australian Institute of Marine Science.

He estimated that among more than 1,000 species found during the three expeditions, 300 to 500 were unknown to science, and he expects more over the next two years as the reefs are revisited.

Detailed analysis has to be carried out yet but the newly catalogued species are thought to include 150 soft corals, 130 crustaceans and up to 100 worms. Urchins, basket stars, which are closely related to starfish, and seaweeds were also among the finds.

“In spite of all our activities we still don’t know what’s under our noses,” he said. “What we’ve found during these three expeditions illustrates the size of the problem.”

“It shows we don’t have to go to the middle of the Pacific or Indian oceans to find new species. They are just off our doorstep.” Data gathered by the survey team will help scientists to build up a picture of the changes in diversity in different parts of the seas.

Previous work has revealed wide differences in the make-up of reef eco-systems, with diversity within species generally decreasing the further they are from the equator.

The Census of Marine Life project aims to provide comprehensive basic information on the make-up of life in the seas, allowing researchers to be able to understand better the effects of any changes in the marine environment.

“Corals face threats ranging from ocean acidification, pollution and warming to overfishing and starfish outbreaks,” said Ian Poiner, of the Australian Institute of Marine Science. A proliferation of starfish can be damaging as some species, particularly the Crown of Thorns, eat coral.

Dr Poiner added: “Only by establishing a baseline of biodiversity and following through with later censuses can people know the impact of those threats and find clues to mitigate them.”

The new isopods, small creatures usually just a matter of millimetres long, were of particular interest to the research team because they are regarded as a valuable indicator of diversity.

Scientists taking part in the project hoped that some of the newly discovered isopods would be found to lead as bizarre lives as those that eat off the tongues of live fish and are already known to be present off the Australian coast.

Ron O’Dor, chief scientist at the census, added: “Amazingly colourful corals and fishes on reefs have long dazzled divers, but our eyes are just opening to the astonishing richness of other life forms in these habitats.

“We must wonder why nature has evolved such prolific diversity on coral reefs. While they are icons of diversity, the processes that have generated and maintained coral reef biodiversity are still unknown.”

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