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

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 destabilizing 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.