( Marine environments around the world ar...)Ships bring alien jellyfish invaders to our shores

Using genetic data and computer simulations of ocean currents and water temperatures, researchers from the University of New South Wales and the University of California, Davis, have revealed that the moon jellyfish could not have migrated naturally, according to a report in today's Proceedings of the National Academy of Sciences journal.

By simulating the movement of the jellyfish ?of the genus Aurelia ?over a 7,000 year period the study provides strong evidence that their world-wide dispersal post-dates European global shipping and trade that began almost 500 hundred years ago.

Recent surveys suggest that up to almost one quarter (23 per cent) of all marine species in international harbours are non-indigenous, according to one of the research authors, Dr Mike Dawson of the University of California, Davis.

"Marine organisms traverse the globe in ballast water, on ship hulls and through the trade of exotic species such as tropical fish and this has potential to displace local marine species, threaten ecosystems and cause billions of dollars in damage and preventive control," says Dawson who tracked the invading jellyfish in Japan, California, western Europe and the east and west Australian coastlines.

Introduced species are believed to cost the United States $122 billion per year. About 3,000 species of marine organisms are believed to travel the world in ships' ballast water each day. Ships take in water for stability before a voyage and despite preventative measures such as mid-ocean exchange/flushing this 'foreign' water and its contents can find their way into bays and harbours at the destination.

The computer model used to track jellyfish movements could answer similar questions about the migration and introduction of any suspected non-native marine
'"/>

Source:University of New South Wales