Food web structure of three Mediterranean stream reaches along a gradient of anthropogenic impact

Abstract

Anthropogenic impact can alter food web structure through changes in species interactions. In this study, we explored the food web of three Mediterranean stream reaches (two seasonal and one permanent) along an anthropogenic impact gradient to test the hypothesis that increasing impact simplifies food webs. To test this, we applied the isotopic (d 13 C and d 15 N) niche concept to compare reaches using isotopic metrics (isotopic richness, divergence, dispersion, evenness, and redundancy). The isotopic indices were useful to identify differences in food web architecture among the three reaches. The least impacted site had the highest isotopic richness, dispersion, and isotopic redundancy, suggesting higher ecological resilience at this site. The effect of disturbance in the remaining two sites was masked by the presence of invasive crayfish, which increased isotopic divergence and was responsible for higher food-chain length in the most impacted reach, but not in the moderately impacted reach. Consumers displayed generalistic feeding habits, with Bayesian mixing models indicating that they relied primarily on a mixture of periphyton, other macroinvertebrates, and to a lesser extent, detritus. Some taxa displayed Handling editor: Marı ´a del Mar Sa ´nchez-Montoya

Land‐use change erodes trophic redundancy in tropical forest streams: Evidence from amino acid stable isotope analysis

“…In the longer term, trophic redundancy also promotes more stable food chains by reducing the likelihood of secondary extinctions (Brodie et al., 2014; Petchey et al., 2008; Sanders et al., 2018). While food chain length and trophic redundancy are both key areas of investigation in food web ecology, the conceptual link between these properties is often underexplored, even when both metrics are featured in the same study (Price et al., 2019; Sroczynska et al., 2020).…”

Traceability and Authentication of Manila Clams from North-Western Adriatic Lagoons Using C and N Stable Isotope Analysis

“…Like other products, the provenance of seafood can be traced using the isotopic ratios of the organism tissues, as the carbon (C) and nitrogen (N) isotopic ratios are functions of the isotopic composition of the food source as well as the fractionation associated with biochemical processes [ 25 , 26 , 27 , 28 ]. However, Briant et al [ 29 ] highlighted that temporal (from seasonal to multi-decadal) climatic variations can shift the isotope composition of mollusks.…”

“…Seasonal variability has been related both to the reproduction cycle of bivalves and to changes in trophic resources, whereas multi-decadal climatic variations can modify the hydrological environment, thus affecting the biological or ecological responses of organisms. In addition, anthropogenic impacts can also alter the food web and the uptake of nutrients [ 28 ]. This, in turn, implies that isotope analyses represent potential tracers for the seafood origin but require the creation of datasets that must be updated periodically.…”

“…This, in turn, implies that isotope analyses represent potential tracers for the seafood origin but require the creation of datasets that must be updated periodically. In particular, manila clams feed exclusively on particles that are naturally present in the water column and on particles resuspended from the sediment [ 2 , 28 ]. Thus, stable isotopes could be used as a proxy to trace the provenance of these organisms, as there is a direct relationship between the isotopic composition of nutrients available in the in the ecosystem and the isotopic composition of consumer tissues [ 28 , 30 , 31 , 32 , 33 ].…”

“…In particular, manila clams feed exclusively on particles that are naturally present in the water column and on particles resuspended from the sediment [ 2 , 28 ]. Thus, stable isotopes could be used as a proxy to trace the provenance of these organisms, as there is a direct relationship between the isotopic composition of nutrients available in the in the ecosystem and the isotopic composition of consumer tissues [ 28 , 30 , 31 , 32 , 33 ]. Therefore, differences in isotopic values among manila clam tissues reflect a change of composition or shift in isotopic values of the relative food source [ 33 ], which can be used as fingerprint to trace the provenance of the organisms.…”