Abstract
Climate warming is predicted to alter routing and flows of energy through food webs because of the critical and varied effects of temperature on physiological rates, community structure, and trophic dynamics. Few studies, however, have experimentally assessed the net effect of warming on energy flux and food web dynamics in natural intact communities. Here, we test how warming affects energy flux and the trophic basis of production in a natural invertebrate food web by experimentally heating a stream reach in southwest Iceland by ~4°C for 2 yr and comparing its response to an unheated reference stream. Previous results from this experiment showed that warming led to shifts in the structure of the invertebrate assemblage, with estimated increases in total metabolic demand but no change in annual secondary production. We hypothesized that elevated metabolic demand and invariant secondary production would combine to increase total consumption of organic matter in the food web, if diet composition did not change appreciably with warming. Dietary composition of primary consumers indeed varied little between streams and among years, with gut contents primarily consisting of diatoms (72.9%) and amorphous detritus (19.5%). Diatoms dominated the trophic basis of production of primary consumers in both study streams, contributing 79–86% to secondary production. Although warming increased the flux of filamentous algae within the food web, total resource consumption did not increase as predicted. The neutral net effect of warming on total energy flow through the food web was a result of taxon-level variation in responses to warming, a neutral effect on total invertebrate production, and strong trophic redundancy within the invertebrate assemblage. Thus, food webs characterized by a high degree of trophic redundancy may be more resistant to the effects of climate warming than those with more diverse and specialized consumers.
| Original language | English |
|---|---|
| Article number | e02952 |
| Journal | Ecology |
| Volume | 101 |
| Issue number | 4 |
| DOIs | |
| Publication status | Published - 1 Apr 2020 |
Bibliographical note
Funding Information:This study was supported by the National Science Foundation (DEB-0949774 and DEB-1354624 to JPB and ADH and DEB-0949726 to WFC). We thank Lauren Davis, David Hernandez, Amanda Keasberry, Elena Nava, Camille Perrett, and Jackie Pitts for help in the laboratory, and Frið�jófur Árnason, Liliana García, Ragnhildur Magnúsdóttir, Ryan McClure, Vija Pelekis, Adam Toomey, Chau Tran, Brooke Weigel, and Tanner Williamson for help in the field. We are grateful to Sigurður Guðjonsson, Guðni Guðbergsson, and the staff at the Veiðimálastofnun for providing laboratory space and logistical support. We are also grateful to Sveinbjörn Stein�órsson at the University of Iceland for super-jeep transport to our field sites during the winter. Art Benke and two anonymous reviewers provided invaluable comments on earlier drafts of the manuscript.
Publisher Copyright:
© 2019 by the Ecological Society of America
Other keywords
- climate change
- energy flow
- experimental warming
- food webs
- rivers
- streams
- trophic basis of production
- trophic redundancy