AUSTRALIAN and Japanese seas share top honours as home to the greatest diversity of ocean life in the world, according to a census. Both nations boast nearly 33,000 species of marine plant, animal and micro-organism, according to the first results of the international 10-year-long Census of Marine Life, reported yesterday in the journal PLoS One.
The oceans off China, the Mediterranean Sea and the oil-soaked Gulf of Mexico round out the top five areas most diverse in known marine species.
The census included known species in 25 biologically significant regions, from the Antarctic through temperate and tropical waters to the Arctic.
Roughly, one-fifth of all species were crustaceans which, combined with molluscs and fish, comprised half of all known species across the globe. While impressive, Australia's tally was not complete, said regional lead author, marine ecologist Alan Butler. "We think we've only seen about 20 per cent of what's there," said Dr Butler, who is with CSIRO Marine and Atmospheric Research in Hobart.
His group concluded there were 32,897 scientifically described species, mostly animals, in databases, many of which go back 200 years. Of those, 130 are introduced species. Among the 58 threatened species are nine species of Brachionichthyidae, Australian handfishes.
"We need to protect this biodiversity," said Dr Butler, who claimed short-term threats came from human activity such as offshore drilling and the impacts of fishing. He said climate change was the greatest long-term threat, triggering shifts in currents and increased acidification of the seas.
Dr Butler speculated that Australia boasted so many species because it was isolated after it broke away from the giant continent Gondwana about 50 million years ago. "There was a long, isolated southern boundary where things could evolve," he said.
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