Astonishing diversity of the oceans revealed in census

Scientists spent ten years attempting to quantify for the first time the diversity of species that live in the seas. The results were reported yesterday in the first Census of Marine Life.

The researchers split the oceans into 25 regions and concluded that on average they are home to about 10,750 species.

However, the seas around Australia, the most abundant, had as many as 33,000 species. The Atlantic ocean around Europe was eighth on the list with 12,270 creatures lurking in its depths.

The researchers believe that for every species recorded, another four are still to be found. Only 5 per cent of the world's oceans have been explored.

Over the course of the work to draw up the census, more than 5,000 new sea creatures were discovered. Of known species listed in the catalogue, about a fifth are crustaceans, such as crabs, lobsters and barnacles.

A further 17 per cent are molluscs, such as squid, clams and sea slugs, and 12 per cent are fish.

One-celled organisms known as protozoa make up 10 per cent of species, and algae make up another 10 per cent.

The category that includes animals such as whales, sea lions, seals and turtles, known as "other vertebrates" makes up just 2 per cent, according to the census, showing that some of the best known marine animals comprise a tiny part of biodiversity.

The scientists have dubbed the striking manylight viperfish the "Everyman" of the deep ocean, because it has been recorded in more than a quarter of marine waters.

The census, which involved more than 360 scientists in 80 countries, will help set a baseline for measuring changes in species diversity. Scientists hope it will also help fashion policies to sustain fisheries, conserve diversity, reverse habitat loss and respond to climate change.

One of the lead authors, Dr Mark Costello of the Leigh Marine Laboratory, at the University of Auckland, New Zealand, said the picture was not complete.

"Sparse, uneven marine sampling in much of the world underlies this initial inventory, and future research will undoubtedly alter the profile presented today," he said.

Scientists believe the tropics, deep seas and southern hemisphere hold the most undiscovered marine species. The proportion of species not yet described is estimated at up to 58 per cent in Antarctica, 38 per cent for South Africa, 70 per cent for Japan, 75 per cent for the Mediterranean deep-sea, and more than 80 per cent for Australia.

Dr Tom Webb, a marine ecologist from the University of Sheffield, who also worked on the census, believes far more needs to be done to explore the deep open ocean.

"It's shocking that in 2010, the International Year of Biodiversity, the largest habitat on Earth remains virtually unexplored."