Exotic species have invaded more than 80 per cent of the oceans and coasts on Earth, causing problems that can ultimately cost billions of dollars to handle and these species may spread even further as climate changes worldwide, scientists find.

Invasive species are infamous for wreaking havoc on land kudzu vines have covered large swaths of the U.S. Southeast; zebra mussels have invaded U.S. waterways, and rabbits and cane toads have bred to huge numbers in Australia.

Now scientists find that 84 per cent of all marine regions harbor invasive species as well, said a marine ecologist. More than half of these are harmful against the invaded territories, she added.

"There are more than 500 non-native species established in U.S. tidal waters," said the ecologists at the American Association for Advancement of Science conference in Washington where she presented her findings.

"Antarctica is important to us not just because of penguins and melting ice, but because it is a very special place for organisms 50 per cent of the species there live in Antarctica and no place else, so it's a very special place for biodiversity," told the scientists.

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When it comes to how these invasions happen, 50 per cent of cases are carried in by ships and boats in ballast and on hulls and 25 per cent have aquaculture farming to blame. The rest of the time, a variety of culprits are at work, including the aquarium trade, the live seafood industry and marine debris, informed the marine ecologist.

Ships carry water as ballast to help stabilize them when they are not hauling cargo. "It's estimated that about 10,000 species are in transport in ballast water every day," said the scientist.

Meanwhile, twice as many species of exotic creatures hitchhike aboard hulls. They cost the shipping industry a whopping $36 billion by increasing the amount of drag they face in the water and thus significantly adding to how much fuel they have to use.

Aquaculture, and particularly shellfish farming, is often seen as a way of providing cheap, healthy seafood in a sustainable manner. However, shellfish farming has inadvertently caused a high number of invasive species to spread, with cultured oysters going feral in 18 countries around the world, including the United States, explained the ecologist.

The aquarium trade has also introduced devastating intruders around the world, including beautiful but venomous lionfish. "These are voracious predators it's amazing how fast they can prey on other fish," the scientist pointed out, adding, "They've spread from the Caribbean up and down the East Coast [of the United States]."

A common aquarium seaweed, Caulerpa, has also invaded California, Australia and the Mediterranean.

Evidence is also building that marine debris, such as that making up the infamous giant patch of garbage in the Pacific, are potential vehicles for invasive species. "We know that non-native species have been found on plastic in areas they do not belong," concluded the marine ecologist.