Light availability is an important factor influencing aquatic food webs and is largely mediated by stream-side vegetation. In forested headwater streams, light availability is almost entirely mediated by the canopy structure of stream-side vegetation. Over the last century, many stream-side forests in the Pacific Northwest were heavily harvested, leading to dense regenerating stands along streams today. Under current conditions algal growth under these dense, closed canopies is highly light limited. We hypothesized that a small, localized release from light limitation will result in reach-scale increases in benthic periphyton biomass, thereby increasing scraping invertebrate abundance and predicted that this change in community structure would be reflected in trout diets. To investigate, we conducted a before-after-control-impact study design using paired reaches. In the treatment reach we cut a 20–40-meter gap in the canopy. In contrast to our expectations, we found that the macroinvertebrate community structure resisted light changes in the presence of a canopy gap and this lack of change was not being masked by increased consumption of scraping invertebrates in summer trout diets. Previous studies have shown large scale removal of stream-side vegetation resulted in changes to primary consumer abundances. The lack of macroinvertebrate community response to small canopy gaps suggests there is a necessary impact size required to elicit responses at higher trophic levels beyond primary production.