Global warming shrinking size of marine species

London: Global warming is causing aquatic animals to shrink 10 times more than land-dwellers in size, scientists say in the largest study of its kind.

The study by researchers from Queen Mary College, University of London, and the University of Liverpool shows that the body size of marine and freshwater species are affected disproportionately by warmer temperatures. The findings could have implications for aquatic food webs and the production of food by aquaculture. Researchers compared the extent to which the adult size of 169 terrestrial, freshwater, and marine species responded to different non-harmful temperatures. "Aquatic animals shrink 10 times more than land-dwellers in species the size of large insects or small fish," said co-author Dr Andrew Hirst. "While animals in water decrease in size by five per cent for every degree Celsius of warming, similarly sized species on land shrink, on average, by just half a per cent," Hirst said. The research also found the most likely cause of the difference in size is due to the much lower availability of oxygen in water than in air. Warming increases the need for oxygen by organisms on land and in water, however aquatic species have a much harder job meeting this increased demand. "To satisfy increased demands for oxygen at higher temperatures, aquatic species have fewer options. Reducing the size at which they mature is their way of balancing oxygen supply and demand," said co-author Dr David Atkinson, of the University of Liverpool. "Given that fish and other aquatic organisms provide three billion people with at least 15 per cent of their animal protein intake, our work highlights the importance of understanding how warming in the future will affect ocean, lake and river dwelling species," said lead author Dr Jack Forster. The research was published in the journal Proceedings of the National Academy of Sciences (PNAS). PTI