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Gulf of Mexico

It is ironic that the Gulf of Mexico should prove to be one of the most biodiverse parts of the ocean, given that it is now facing the Deepwater Horizon oil spill, not to mention the huge pre-existing “dead zone” caused by fertiliser run-off from US farms.

It boasts over 15,000 known species spread over just 1.5 million square kilometres of ocean – a far higher species density than the seas around Australia, whose 40,000 known species sprawl over 13.6 million square kilometres.

This Venus fly trap anemone was found at a depth of 1500 metres. Like the land plant of the same name, it closes its tentacles to trap its prey.

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(Image: I. MacDonald)

Australia

The seas around Australia are some of the richest on Earth. Around 40,000 species are recorded as living there, with the actual total thought possibly to be as high as 250,000 – and this does not even include the nearby Great Barrier Reef.

Almost half this diversity is accounted for by molluscs (25 per cent) and crustaceans (19 per cent), rather than more conspicuous creatures such as whales and turtles. This pattern is repeated throughout the world.

This lives deep in the dark, cold depths of Australia’s oceans. Food is hard to come by so it has to keep hold of it when it finds it – which is why it has teeth on its tongue.

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(Image: Julian Finn, Museum Victoria)

Japan

This new species of sea snail was discovered living on a sperm-whale carcass that had sunk to the sea floor. Its tiny eyes (bottom right) are protected by shields built onto its head.

Japan’s coastal waters are home to over 155,000 species, although little is known about 120,000 of these. This makes it one of the most diverse areas in the entire ocean, along with Australian and Chinese waters.

But the region faces many threats, including the recently introduced “killer alga” – one of the most damaging invasive species known.

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(Image: Yoshihiro Fujiwara/JAMSTEC)

South Africa

like this one live all around the world, but they are particularly common off South Africa’s Western Cape, where tourists flock for the chance to cage-dive with them.

They are just one of 12,900 known species that make their homes in South Africa’s 1 million square kilometres of coastal waters. Yet almost nothing is known of what lives at depths of more than 1000 metres. Some 83 per cent of the known species were found at 100 metres or less, so the true number is likely to be much greater.

of the University of Auckland says that South Africa is particularly rich in endemic species: those that are found nowhere else.

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(Image: Howard Huang/Rex Features)

Caribbean

The Caribbean is best known for its coral reefs, mangroves and sea gardens. Over 12,000 species are known, from an area of 2.75 million square kilometres.

This is found on coral reefs, where it makes its home inside living sponges. It is active at night.

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(Image: César Herrera)

Mediterranean

The deepest waters of the Mediterranean were thought to be sparsely populated, but the Census of Marine Life says life is abundant there.

One such species is the heart urchin, (see picture), which lives buried in muddy and sandy sediments. It bulldozes its way through the sediment in search of food, in the process allowing oxygen to penetrate deeper and thus .

The Mediterranean’s 17,000 species face an unusually severe threat from litter, because the sea is almost entirely enclosed by land and endures heavy shipping traffic. The wars in the former Yugoslavia also led to ammunition and bombs being dumped there.

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(Image: Bernard Picton)

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