Agricultural land-use change seasonally rewires stream food webs: a case study from headwater streams in the Lake Erie watershed

Abstract

Human impacts, like agricultural land-use change, alter natural patterns of resource availability and consumer response through space and time threatening the stability of ecosystems. In streams, removal of riparian zones and nutrient loading through agriculture may alter seasonal asynchronous resource fluxes and lead to food web rewiring and stability loss. Here, we seasonally sampled three streams across an agricultural gradient to determine how agricultural land-use change rewires seasonal stream food web structures. We show that agricultural land-use change seasonally rewired trophic interactions through reduced terrestrial energy use and trophic position. Additionally, agricultural land-use change drove steeper biomass size spectrum slopes and shifted fish communities to high abundances of small individuals. Collectively, our results suggest agricultural land-use change may be homogenizing stream food webs towards productive, single-energy channel dominated webs with faster turnover rates. Theory predicts such changes are indicative of instability, suggesting agriculture may be destabiliz-ing stream food webs. Importantly, our results indicate agricultural land-use strategies that aim to retain riparian zones and reduce nutrient run-off may be important for reducing potential destabilizing effects. As agriculture is expected to increase to support growing human populations, elucidating strategies to maintain resilient stream food webs in agricultural landscapes is essential.