Mechanisms of trophic niche compression: evidence from landscape disturbance

1. Natural and anthropogenic disturbances commonly alter patterns of biodiversity and ecosystem functioning. However, how networks of interacting species respond to these changes remains poorly understood. We described aquatic food webs using invertebrate and fish community composition, functional traits, and stable isotopes from twelve agricultural streams along a landscape disturbance gradient.

2. We predicted that excessive deposition of fine inorganic sediment (sedimentation) associated with agricultural activities would negatively influence aquatic trophic diversity (e.g., reduced vertical and horizontal trophic niche breadths). We hypothesized that multiple mechanisms might cause trophic niche ‘compression’, as indicated by changes in realized trophic roles.

3. Food-web properties based on consumer stable isotope data (δ13C and δ15N) showed that increasing sediment disturbance was associated with reduced trophic diversity. In particular, the aquatic invertebrate community oc...