RESPONSE OF FOOD WEBS TO STREAM RESTORATION

Food webs represent the flux of matter within interacting communities. They are an ideal tool to assess the success of ecosystem restoration measures as they integrate structural and functional aspects of communities. Based on stable isotopes (δ¹³C and δ¹⁵N) of benthic invertebrates, we analyzed here the recovery of food webs after stream restoration with respect to hydro-morphology and waste water pollution. In a long-term dataset following up to 28 years after restoration, we could show clear responses of food web metrics to restoration. While the trophic similarity as a proxy for functional redundancy showed consistently positive relationships with time since restoration, the responses of other metrics such as food chain length and trophic diversity were less consistent over sites. Instead, they showed site-specific responses including both positive as well as negative trends with time since restoration. On that basis, we performed intense analyses of sites with different restoration ages including resource and consumer stable isotope analyses as well as consumer gut content analyses in order to detect mechanisms for the different responses. First results suggest that the prey diversity of higher trophic levels is significantly reduced in restored compared to near-natural sites despite long recovery times and recovery of overall taxa richness. Together with the strong restoration effects on trophic diversity, this underlines the value of food web analyses besides common community analyses to understand the conditions for full recovery of ecosystems. 

Presentation Preference: Oral

Primary Presenter: Markus Weitere, Helmholtz-Centre for Environmental Research - UFZ (markus.weitere@ufz.de)

Authors:

Alexandra Schlenker, Helmholtz-Centre for Environmental Research - UFZ  (alexandra.schlenker@ufz.de)

Mario Brauns, Helmholtz-Centre for Environmental Research - UFZ  (mario.brauns@ufz.de)

Patrick Fink, Helmholtz-Centre for Environmental Research - UFZ  (Patrick.fink@ufz.de)

Armin Lorenz, University of Duisburg-Essen  (armin.lorenz@uni-due.de)

Markus Weitere, Helmholtz-Centre for Environmental Research - UFZ  (markus.weitere@ufz.de)