Wood mitigates the effect of hydropeaking scour on periphyton biomass and nutritional quality in semi-natural flume simulations
The daily fluctuating discharge from hydroelectric power plants, known as hydropeaking, has been shown to cause catastrophic drift in aquatic insect communities and limit secondary production, but relatively little attention has been given to its effects on periphyton, an important food resource for consumers. We simulated daily 5-h hydropeaking events over the course of 5 days in spring and summer in an open air, experimental flume system fed by a pristine 2nd order stream in the Italian Alps. We hypothesized that hydropeaking would suppress periphyton biomass and especially nutritional quality (i.e., fatty acid content). Hydropeaking resulted in decreased periphyton Chl-a and AFDM on tiles, but there was no corresponding loss on wood. Hydropeaking did not alter periphyton elemental nutrient stoichiometry but led to a disproportionate loss of periphyton fatty acid content on both substrates. Ordination of overall fatty acid profiles indicated different periphyton fatty acid profiles by substrate and a shift from physiologically important highly-unsaturated fatty acids to non-essential saturated fatty acids after hydropeaking. These results suggest that hydropeaking may have the potential to depress primary biomass and nutritional quality in downstream ecosystems, and that availability of wood substrate may mitigate part, but not all, of this effect. Since food nutritional quality, especially fatty acid content, has been suggested to be a limiting resource on production in aquatic systems, this may generate an indirect and potentially overlooked limiting effect on aquatic consumers in hydropeaking-impacted alpine rivers.
KeywordsFatty acids Hydropeaking Hydropower Wood Alpine stream Artificial flumes
The authors wish to thank the Servizio Bacini Montani of the Autonomous Province of Trento for building and maintaining the flumes, Lorenzo Forti and Martino Salvaro (Department of Environmental, Civil and Mechanical Engineering of the University of Trento) for their help in setting up and conducting the experiments, and Bruno Maiolini (Fondazione E. Mach), Stefano Mauro, Lorenzo Colaianni, Andrea Bertoncin, Mauro Carolli, Sonia Endrizzi, and Sofia Biffi for help in the field. We would also like to thank Lorena Reiss (Fondazione E. Mach), Angela Krüger (IGB), and Katrin Premke (IGB) for assistance in the lab. This research was carried out within the Erasmus Mundus Doctorate Program SMART (http://www.riverscience.eu) funded by the Education, Audiovisual and Culture Executive Agency (EACEA) of the European Commission.
- Abbe TB, Brooks AP, Montgomery DR (2003) Wood in river rehabilitation and management. In: Gregory SV, Boyer KL, Gurnell AM (eds) The Ecology and Management of Wood in World Rivers. American Fishery Society Symposium 37, Bethesda, pp 367–389Google Scholar
- Céréghino R, Cugny P, Lavandier P (2002) Influence of intermittent hydropeaking on the longitudinal zonation patterns of benthic invertebrates in a mountain stream. Int Rev Hydrobiol 87:47–60. doi: 10.1002/1522-2632(200201)87:1<47:AID-IROH47>3.0.CO;2-9 CrossRefGoogle Scholar
- Fox J, Weisberg S (2011) An R companion to applied regression, 2nd edn. Sage, Thousand Oaks. http://socserv.socsci.mcmaster.ca/jfox/Books/Companion. Accessed 4 Mar 2016
- Kopp JF, McKee GD (1979) Methods for chemical analysis of water and wastes National Technical Information Service Springfield, Va, Report No PB 297686 (32319):490Google Scholar
- Montgomery DR, Collins BD, Buffington JM, Abbe TB (2003) Geomorphic effects of wood in rivers. In: Gregory SV, Boyer KL, Gurnell AM (eds) The ecology and management of wood in world rivers. American Fishery Society Symposium 37, Bethesda, pp 21–47Google Scholar
- Oksanen, J, et al. (2013) Vegan: community ecology package. R package version 2.0-10. http://CRAN.R-project.org/package=vegan. Accessed 4 Mar 2016
- Rosario-Martinez H (2013) phia: post hoc interaction analysis. R package version 0.1–3. http://CRAN.R-project.org/package=phia. Accessed 4 Mar 2016
- Stevenson RJ, Bahls LL (1999) Periphyton protocols revision to rapid bioassessment protocols for use in streams and rivers: periphyton, Benthic macroinvertebrates, and fish. http://nepis.epa.gov/. Accessed 7 Apr 2016