Global warming and shifts in food web strucutre

Predicting the effects of global warming on biological systems is of critical importance for informing proactive policy decisions. Most research so far has been on trying to predict shifts in species distributions and changes in interactions within local habitats. But what many of these studies assume is that the basic biological processes and requirements of the individual species will not change -that is their biology is fixed and they simply need to find the place that best suits them. Not so, say Mary O'Connor and colleagues, in a just-released study in PLoS Biology.

O'Connor and colleagues experimentally warmed marine microcosms and tested two alternative hypotheses on food web structure: 1) that productivity increases with warming; and 2) warming increases metabolic rates, thus changing consumer-autotroph (i.e., primary producers) interactions. What they found was that warming indeed altered consumer-autotroph interactions. Warming increased base metabolic rates of consumers, as well as primary production, and the net effect was that food webs shifted towards increasing consumer control (i.e., top-down control).

What this research means is that global warming may alter food web interactions by increasing resource needs of organisms as their metabolic rates increase. This may increase the stress on communities and change diversity patterns as increased needs may shift competitive hierarchies or affect autotroph's ability to withstand consumer effects.

O'Connor, M., Piehler, M., Leech, D., Anton, A., & Bruno, J. (2009). Warming and Resource Availability Shift Food Web Structure and Metabolism PLoS Biology, 7 (8) DOI: 10.1371/journal.pbio.1000178