PRIMARY RESEARCH PAPER Variability of water temperature may influence food-chain length in temperate streams Nicolas Hette-Tronquart • Jean-Marc Roussel • Bernard Dumont • Virginie Archaimbault • Didier Pont • Thierry Oberdorff • Je ´ro ˆme Belliard Received: 2 July 2012 / Revised: 24 June 2013 / Accepted: 18 July 2013 / Published online: 4 August 2013 Ó Springer Science+Business Media Dordrecht 2013 Abstract Food-chain length (FCL) is commonly used in ecological investigations to gain insight into how ecosystems function. Several studies have inves- tigated the mechanisms underlying FCL patterns, but none has specifically examined the effect of tempera- ture variability. In river ecosystems, water temperature variability can modify community structure, individu- als’ activity, and individuals’ physiological rates, among other things. As such, we expected that it would negatively influence FCL. To test this prediction, we took advantage of a dataset comprising five streams, which mainly differ according to their temperature variability. At each stream, we (i) studied the species composition of macroinvertebrates and fish, and using nitrogen and carbon stable isotopes, (ii) estimated realized FCL, and (iii) examined food web structure. For macroinvertebrates, but not for fish, species com- position differed among sites displaying low and high temperature variability. FCL was negatively influenced by temperature variability. Confirming this trend, we found a highly significant linear relationship between FCL and temperature variability using data from the literature. As for food web structure, the trophic position of filter-feeders/shredders may explain the FCL differences among sites. Our study gives addi- tional support to the ‘‘dynamic stability’’ hypothesis and advances a step further by suggesting that temper- ature variability alone may reduce FCL. Keywords Stable isotopes  Trophic position  Food web  Macroinvertebrates  Salmo trutta  Cottus gobio Introduction Knowledge of food webs is essential to understanding how ecosystems function. Food webs provide the Electronic supplementary material The online version of this article (doi:10.1007/s10750-013-1613-7) contains supple- mentary material, which is available to authorized users. Handling editor: M. Power N. Hette-Tronquart (&)  V. Archaimbault  D. Pont  J. Belliard Irstea, UR HBAN, 1 rue Pierre-Gilles de Gennes, CS 10030, 92761 Antony, France e-mail: nicolas.hette@edu.mnhn.fr J.-M. Roussel INRA, UMR 985 ‘‘Ecologie et Sante ´ des Ecosyste `mes’’, 65 rue de Saint-Brieuc, 35042 Rennes, France B. Dumont Irstea, UR HYAX, 3275 Route de Ce ´zanne, CS 40061, 13182 Aix-en-Provence, France T. Oberdorff UMR CNRS 7208-IRD 207-MNHN-UPMC ‘‘Biologie des Organismes et Ecosystemes Aquatiques’’, DMPA, Museum National d’Histoire Naturelle, 43 rue Cuvier, 75005 Paris, France 123 Hydrobiologia (2013) 718:159–172 DOI 10.1007/s10750-013-1613-7