Global warming poses threat to food chains

Rising temperatures could reduce the efficiency of food chains and threaten the survival of larger animals, new research shows.

The study was conducted by the University of Exeter and Queen Mary University of London. Lead author Diego Barneche is an adjunct member of the UWA Oceans Institute and has recently joined the Australian Institute of Marine Science.

The research team measured the transfer of energy from single-celled algae (phytoplankton) to small animals that eat them (zooplankton) over seven years in an artificially warmed pond.

The results suggest that 4°C of warming  - a scenario that is on track with current predictions for temperature rises by the end of the century - reduced energy transfer in the plankton food webs by up to 56%.

In general, about 10% of energy produced on one level of a food web 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.

Dr Diego Barneche

Warmer conditions increase the metabolic cost of growth, leading to less efficient energy flow through the food chain which reduces the energy available to predators in the next level up the food web.

"These findings shine a light on an under-appreciated consequence of global warming," said Professor Gabriel Yvon-Durocher, of the University of Exeter.

"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."