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Coastal ecosystems home to growing jellyfish population

A first-ever study of jellyfish abundance shows that these free-swimming medusas are growing in number in many of the large marine ecosystems worldwide, such as river basins and estuaries, seaward boundaries of continental shelves and coastal currents. Presented in the journal...

A first-ever study of jellyfish abundance shows that these free-swimming medusas are growing in number in many of the large marine ecosystems worldwide, such as river basins and estuaries, seaward boundaries of continental shelves and coastal currents. Presented in the journal Hydrobiologia, the British-Canadian study put various jellyfish species for 45 of 66 large marine ecosystems in the spotlight, finding that an increasing number of these creatures are found in the Mediterranean, the Black Sea, east Asia, the north-east United States Continental Shelf, Hawaii and Antarctica. Scientists from the University of British Columbia in Canada and the University of East Anglia in the United Kingdom stratified data by the large marine ecosystems to investigate and compare changes in the populations of the jellyfish. 'There has been anecdotal evidence that jellyfish were on the rise in recent decades,' explains lead author Lucas Brotz, a doctoral student at the University of British Columbia. 'But there hasn't been a global study that gathered together all the existing data until now. Our study confirms these observations scientifically after analysis of available information from 1950 to the present for more than 138 different jellyfish populations around the world.' While they only move in the direction that currents take them, jellyfish have a direct impact on human activities. They sting swimmers, clog intakes of power plants and challenge even fishermen. But it should be noted that some jellyfish species are a food source in various parts of the globe. 'By combining published scientific data with other unpublished data and observations, we could make this study truly global and offer the best available scientific estimate of a phenomenon that has been widely discussed,' says Daniel Pauly, a professor at the University of British Columbia and one of the authors of the study. 'We can also see that the places where we see rising numbers of jellyfish are often areas heavily impacted by humans, through pollution, overfishing and warming waters.' According to Professor Pauly, increasing human activities in marine habitats may have contributed to the rise in anecdotal reports of jellyfish abundance. This study offers researchers a solid baseline for future studies. The findings also identified a drop in jellyfish abundance in 7% of coastal regions. The team observed no obvious trend for the remainder of the marine ecosystems. 'This study represents the first rigorous demonstration that jellyfish populations appear to be increasing in coastal ecosystems worldwide, as previously suggested,' the authors write. 'Of the 45 large marine ecosystems included in our analysis, 28 (62%) showed increasing trends, while only 3 (7%) showed decreasing trends. The remaining 14 large marine ecosystems (31%) were classified as stable/variable, with no obvious trend. These results suggest that while increases of jellyfish populations are not universal, they are both numerous and widespread.' The researchers say it is important to provide greater insight into jellyfish populations, especially because they 'seem to be one of the few groups of organisms that may benefit from the continued anthropogenic impacts on the world's biosphere'.For more information, please visit: University of British Columbia:http://www.ubc.ca/University of East Anglia:http://www.uea.ac.uk/Hydrobiologia:http://www.springer.com/life+sciences/ecology/journal/10750

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