Aquatic Animals Shrink in Warmer Temperature

Focusing on the warmer temperatures, the scientists from Queen Mary, University of London and the University of Liverpool suggest that, warmer temperatures have greater effect on the aquatic life than the land dwellers.

According to the study, warmer temperatures cause greater reduction in the adult sizes of aquatic animals when compared to those of the land dwellers.

This is the first study that demonstrates the body size of marine and freshwater species are affected excessively by warmer temperatures. This could have direct implication for aquatic food webs and the production of food by aquaculture.

In order to prove the hypothesis, the researchers compared the extent to which the adult size of 169 terrestrial, freshwater, and marine species responded to different non-harmful temperatures.

What they noticed was reported by co-author Dr Andrew Hirst from Queen Mary's School of Biological and Chemical Sciences, who stated, "Aquatic animals shrink 10 times more than land-dwellers in species the size of large insects or small fish. While animals in water decrease in size by 5 percent for every degree Celsius of warming, similarly sized species on land shrink, on average, by just half a percent."

Through the research the scientists also state that the most likely cause of this 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. And the aquatic species struggle when faced with such challenge.

Co-author Dr David Atkinson of the University of Liverpool explains: "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."

Lead author Dr Jack Forster also from Queen Mary's School of Biological and Chemical Sciences adds: "Given that fish and other aquatic organisms provide 3 billion people with at least 15 percent 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."

The research was published Nov 5 in Proceedings of the National Academy of Sciences (PNAS).