Seas surrounding an archipelago near the tip of the Antarctic peninsula are richer in animal life than the Galapagos Islands, challenging the notion that warm seas in tropical zones are higher in biodiversity, scientists claimed today.

Much less is known about the South Orkney islands than the tropical islands that helped to shape Charles Darwin's thoughts about natural selection on his Beagle voyage. But according to a new study published today by the Journal of Biogeography, the sea around them is teeming with a huge variety of life. The survey disproves the notion that the waters in chilly polar regions have a much poorer variety of fauna.

"There has been a long-held belief that the tropics are rich and the polar regions are poor and mid-latitudes are somewhere in between," said Dr David Barnes at the British Antarctic Survey, who led the study, part of the international Census of Marine Life. "This is the first time we've been able to actually look at the fauna of a polar archipelago – it is not actually that poor at all."

Barnes said the reason for carrying out the survey was to give a baseline from which changes in biodiversity due to global warming can be judged. "This is in the part of the world with fastest change in terms of temperature," he said.

The Antarctic peninsula has already experienced warming of 3C over the past 50 years. "If you don't know what the fauna is at any one point it is very difficult to detect either species moving in or species moving out", he added.

The survey recorded 1,224 species in 50 different biological classes. The team discovered five new species and one genus - the biological category that is higher than species - that was new to science. The new species are all sea mosses (bryozoans) or isopods (woodlouse-like animals) but they have not been given names yet.

The team also scoured reports from scientific expeditions and the scientific literature going back decades to find every mention of species observed in the region in a bid to create the most complete and authoritative list of creatures that have ever been found there.

But studying the sea creatures off the South Orkneys is not for the faint hearted - and a far cry from the balmy waters around the Galapagos. Barnes's team had to brave biting winds that frequently stopped them from working.

And while diving in the freezing waters, they had to keep an eye out for potential attacks by orcas and leopard seals. If either predator came near they had to stop diving by climbing onto the British Antarctic Survey's Royal research vessel James Clark Ross or scrambling to shore.

"Although that sounds dramatic, weather is a far bigger issue," said Barnes. "It stops us working far more and makes our work far more hazardous ... Sometimes it's much warmer under the water - it's only minus one and a half [degrees]!"

Once underwater though the view is spectacular. "," said Barnes, who has dived extensively on coral reefs and all over the world.

"I don't think I've been anywhere where you can see so many different types of major groups of animals all in one place.

"You would have to swim quite a long way in the UK or maybe cover hundreds of metres in a coral reef to see so many types of animals that you can see in a very small space at the polar regions."

He said that the marine environment off the South Orkneys is also pristine and free from invasive species. "It is literally the only place in the world where you can dive and not see alien species. Everything you can see in front of you is native to Antarctica."

None of the trawls of the ocean depths brought up any plastic waste – something expected anywhere else in the world. The only human crafted item the team did uncover was a piece of lead shot that was probably fired by whalers who used the South Orkneys as a base at the turn of the last century.

The team's survey covered all realms of sea life. As well as diving in the shallows they also trawled the sea bottom to a depth of 1,500m using nets and employed a special sled that when dragged across the bottom could collect even very tiny creatures. Its sieve held everything bigger than 0.3mm.

Other team members combed the intertidal zone of the islands to survey life in rock pools and living on the shore.