Increasing Temperature Decreases Body Size in Aquatic Animals

Written by on November 6, 2012 in Marine Life
Smallmouth grunt and elkhorn coral.

Smallmouth grunt and elkhorn coral. Photo credit: NOAA.

A new study reveals that climate change will cause aquatic animals to decrease in size more than terrestrial animals.

A decline in size is to be expected, as animals that rely on the environment to regulate their body temperatures generally don’t grow as large in extra-warm or extra-cold conditions; however, the exact reason for this temperature-size rule is still unknown.

The researchers reviewed experiments that tested how different organisms’ mass changed with temperature. The experiments were performed on 169 adult terrestrial, marine and freshwater species. They found that aquatic animals experience more of a decrease in body size than terrestrial animals.

“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,” explained Dr. Andrew Hirst from Queen Mary’s School of Biological and Chemical Sciences.

What this means is the temperature-size response is greater in aquatic animals than terrestrial animals.  In addition, the results led the authors to conclude that oxygen requirements are the main factor in the relationship between temperature and body size.

“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,” explained co-author Dr. David Atkinson from the University of Liverpool.

“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,” concluded lead author Dr. Jack Forster.

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Copyright © 2012 by Marine Science Today, a publication of Marine Science Today LLC.

About the Author

About the Author: Emily Tripp is the Publisher and Editor of She holds marine science and biology degrees from the University of Miami's Rosenstiel School of Marine and Atmospheric Science and a Master of Advanced Studies degree in Marine Biodiversity and Conservation from Scripps Institution of Oceanography. When she's not writing about marine science, she's probably running around outside or playing with her dog. .


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