Warming alters the metabolic balance of ecosystems

Abstract

The carbon cycle modulates climate change, via the regulation of atmospheric CO 2 , and it represents one of the most important services provided by ecosystems. However, considerable uncertainties remain concerning potential feedback between the biota and the climate. In particular, it is unclear how global warming will affect the metabolic balance between the photosynthetic fixation and respiratory release of CO 2 at the ecosystem scale. Here, we present a combination of experimental field data from freshwater mesocosms, and theoretical predictions derived from the metabolic theory of ecology to investigate whether warming will alter the capacity of ecosystems to absorb CO 2 . Our manipulative experiment simulated the temperature increases predicted for the end of the century and revealed that ecosystem respiration increased at a faster rate than primary production, reducing carbon sequestration by 13 per cent. These results confirmed our theoretical predictions based on the differential activation energies of these two processes. Using only the activation energies for whole ecosystem photosynthesis and respiration we provide a theoretical prediction that accurately quantified the precise magnitude of the reduction in carbon sequestration observed experimentally. We suggest the combination of whole-ecosystem manipulative experiments and ecological theory is one of the most promising and fruitful research areas to predict the impacts of climate change on key ecosystem services.

Climate change and freshwater ecosystems: impacts across multiple levels of organization

“…Meerhoff et al 2007). Some of these experimental manipulations are still running several years after their inception: 24 ponds in Silkeborg (Denmark) have been warmed continuously since 2003 (Liboriussen et al 2005), another set of 20 ambient/warmed ponds at the FBA River Lab in Dorset (UK) have been running since 2006 (Yvon-Durocher et al 2010) and 48 similar-sized ponds have also been subjected to a comparable level of warming in Ness Gardens at the University of Liverpool (UK) since 1998, albeit intermittently (e.g. McKee et al 2003).…”

“…Liboriussen et al 2005) and England (e.g. Moss et al 2003;Yvon-Durocher et al 2010), seem particularly well-suited to addressing these questions at an appropriate scale and organizational level, and some have already revealed important interactions between the effects of nutrient enrichment and warming on ecosystem functioning and community structure (e.g. Feuchtmayr et al 2009).…”

“…McKee et al 2003). The former have been used to assess shifts in community structure and ecosystem properties, both of which responded to elevated temperatures, as the ponds tended towards more turbid, planktondominated systems at higher temperatures (Meerhoff et al 2007), and the FBA set-up has revealed that warming pushes the systems towards increased heterotrophy and reduced CO 2 sequestration (Yvon-Durocher et al 2010).…”

“…McKee & Atkinson 2000) rather than the higher levels of organization (i.e. communities, food webs, ecosystems) (but see Kishi et al 2005;Burgmer et al 2007;Buisson et al 2008;Friberg et al 2009;Woodward et al 2009;Yvon-Durocher et al 2010). This is especially true for fresh waters, and this is a cause for considerable concern because climate change will not only affect all organizational levels (e.g.…”

Energetic differences between bacterioplankton trophic groups and coral reef resistance

“…Our metabolic rate predictions are dependent on the assumption that the effective activation energy for oxygenic photosynthesis (E ¼ 0.32 eV, range ¼ 0-308C) is lower than the average energy of activation for the biochemical reactions of the Krebs cycle (E ¼ 0.61 eV). This assumption is empirically supported [34][35][36] and has been used to predict metabolic rates for planktonic organisms in both freshwater and marine ecosystems [33,36,37]. Increasing T and/or reducing E increases chemical reaction rates (equation (1.1)).…”