Rising temperatures limit the efficiency of the food chain

Global warming is reducing the efficiency of food chains and threatening the survival of larger animals, according to a study from the University of Exeter.

Single-celled algae called phytoplankton transfer energy to the small animals that eat them. The researchers found that four degrees Celsius of warming reduced energy transfer in the plankton food webs by a much as 56 percent.

Rising temperatures increase the metabolic cost of growth, which leaves less energy available to flow through the food chain. Less energy in the food chain ultimately leads to a reduction in overall biomass.

“These findings shine a light on an under-appreciated consequence of global warming,” said Professor Gabriel Yvon-Durocher. “Phytoplankton and zooplankton are the foundation of food webs that support freshwater and marine ecosystems that humans depend on.”

“Our study is the first direct evidence that the cost of growth increases in higher temperatures, limiting the transfer of energy up a food chain.”

Professor Mark Trimmer of Queen Mary University of London noted that if the effects found in this experiment are evident in natural ecosystems, the consequences could be profound.

“The impact on larger animals at the top of food chains – which depend on energy passed up from lower down the food chain – could be severe. More research is needed,” said Professor Trimmer.

Dr. Diego Barneche of the University of Western Australia explained that about 10 percent of the energy produced on one level of a food chain makes it up to the next level.

“This happens because organisms expend a lot of energy on a variety of functions over a lifetime, and only a small fraction of the energy they consume is retained in biomass that ends up being eaten by predators.”

“Warmer temperatures can cause metabolic rates to accelerate faster than growth rates, which reduces the energy available to predators in the next level up the food web.”

The study is published in the journal Nature.

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By Chrissy Sexton, Earth.com Staff Writer