Seasonal and temporal variation in the effects of forest thinning on headwater stream benthic organisms in coastal British Columbia

•One of few studies on effects of variable retention harvest on stream communities.•Year-round effects of logging on light and biofilm biomass in streams.•Logging increased stream temperature variability but not magnitude.•Effect of harvest on invertebrate abundance and species richness highly seasonal.•Increases in Chironomidae and Simuliidae abundance drive change in community composition.