Dataset for: Intercontinental analysis of temperate steppe stream food webs reveals consistent autochthonous support of fishes

Quantifying the trophic basis of production for freshwater metazoa at
broad spatial scales is key to understanding ecosystem function and has
been a research priority for decades. However, previous lotic food web
studies have been limited by geographic coverage or methodological
constraints. We used compound-specific stable carbon isotope analysis of
amino acids to estimate basal resource contributions to fish consumers in
streams spanning grassland, montane, and semi-arid ecoregions of the
temperate steppe biome on two continents. Across a range of stream sizes
and light regimes, we found consistent trophic importance of aquatic
resources. Essential amino acids of heterotrophic microbial origin
generally provided secondary support for fishes, while terrestrial carbon
did not seem to provide any significant, direct support. These findings
provide strong evidence for the dominant contribution of carbon to
higher-order consumers by aquatic autochthonous resources (primarily) and
heterotrophic microbial communities (secondarily) in temperate steppe
streams.