Líffræðifélag Íslands
Líffræðiráðstefnan 2015

Erindi/veggspjald / Talk/poster E78

Temperature dependence of resource availability determines energy flow through food webs

Eoin O'Gorman (1), Lei Zhao (1), Dan Reuman (2), Guy Woodward (1)

1. Imperial College London, 2. University of Kansas

Kynnir / Presenter: Eoin O'Gorman

Tengiliður / Corresponding author: Eoin O'Gorman (e.ogorman@imperial.ac.uk)

Warming predictions for the forthcoming century are expected to cause extinctions of large predators, while promoting an increased prevalence of small organisms. This is likely to alter the relationship between average species body mass and population abundance in natural communities, with important implications for resource partitioning and energy usage. Here, we used a set of geothermal streams to explore the impact of temperature on mass-abundance scaling in a natural setting. We found that the predicted steepening of the mass-abundance relationship was not realised in the warmer streams, with the opposite effect occurring. A mechanistic model revealed that this pattern only occurs for our data when the carrying capacity of the system does not decrease with temperature to the extent predicted by metabolic theory. We suggest that this is due to constant renewal of nutrient supply in headwater streams. Surprisingly, the body mass of invertebrate consumers increased with temperature, resulting in lower mass-specific metabolic requirements and a greater overall biomass. Our model revealed that this pattern sustained an apex fish predator in the system above a threshold temperature, despite its high metabolic demands. These findings highlight the contingency of community-level ecological responses to warming: when nutrient supply meets metabolic demand, many of the classic predicted temperature responses can be violated.