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Ships bring alien jellyfish invadersMarine environments around the world are being threatened by exotic species of moon jellyfish being dispersed by international shipping, according to research by Australian scientists. Using genetic data and computer simulations of ocean currents and water temperatures, researchers from UNSW and the University of California, Davis, have revealed that the jellyfish could not have migrated naturally, they report in Proceedings of the National Academy of Sciences journal. By simulating the movement of the jellyfish over a 7,000-year period the study provides strong evidence that their world-wide dispersal post-dates European global shipping and trade, which began almost 500 years ago. Recent surveys suggest that almost one quarter (23 per cent) of all marine species in international harbours may be non-indigenous, according to one of the research authors, Dr Mike Dawson from the University of California, Davis. 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 on a daily basis. 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 its 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 creatures, according to its developers, UNSW oceanographers, Associate Professor Matthew England and Alex Sen Gupta. "Up until now our knowledge of natural and human-assisted dispersal of species has been insufficient to confidently track and predict the spread of non-indigenous marine species," says Professor England. "Now we have a tool that can include data on currents, geography and the biology of an organism to help separate natural dispersal from that which happens through shipping and trade," he says. "It's a pretty sophisticated model and we plan to make it available as a research tool on the worldwide web." Discovery: new species of moon jellyfishThe researchers also discovered that there are far more species of moon jellyfish than previously thought. "We identified 16 species of moon-jellyfish, revealing that marine biodiversity is actually much higher than was thought previously," Dr Dawson says. "In retrospect it's easy to see how this wasn't noticed until now. "When you examine moon jellyfish from locations from around the world they look very similar. It's only when you analyse their DNA, as we did, that it becomes obvious that they're very different. "This means that traditional methods that compare physical characteristics can benefit from modern techniques such as DNA analysis," he says. Funding declaration: Media contact: |
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