Using one of our long-term datasets on stream water quality and fish assemblages in and around the metropolitan area of Columbus, OH, we examined the additive, synergistic, and antagonistic effects of multiple urban stressors on fish-based ecological networks. Both unweighted (simple node-link network topology) and bio-mass weighted (species links are weighted by biomass) networks were employed to generate the network indices: linkage density (average number of links per species), connectance (fraction of all possible links realized in a network), and compartmentalization (degree to which networks contain discrete sub-webs), mean link weight (the magnitude of trophic interactions among species in a network), and strength standard deviation (the distribution of total magnitude of all trophic interactions per species in a network). Urban stressors (sedimentation, percent impervious surface, and nutrient concentrations) and stream size (covariate) were used to predict variation network indices. While stream size was an important covariate, sedimentation had strong negative relationships with all network indices. Synergistic effects on network topology were realized through decreased sedimentation and increased stream size, while antagonistic effects emerged from interactions between sedimentation and percent impervious surface and between percent impervious surface and nutrient concentrations on mean link weight. Our results highlight the importance of studying multiple urban stressors simultaneously as they can and do interact in nature.
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