Colonization and production of macroinvertebrates on artificial substrata: upstream–downstream responses to a leaf litter exclusion manipulation

Abstract

1. Macroinvertebrate colonization dynamics were examined on artificial substrata in a stream with terrestrial litter inputs excluded, downstream of the litter‐exclusion treatment, and in a reference stream. 2. Short‐term examination of the rates of organic matter accrual and invertebrate colonization demonstrated significantly lower accumulation of leaf detritus and invertebrates in the litter‐excluded reach and a short distance downstream of that reach. 3. All major fractions of organic matter and invertebrates declined on artificial substrata during the 3‐year litter exclusion. Further, secondary production on artificial substrata in the litter‐excluded reach decreased from 6.2 to 1.5 g AFDM m −2 year −1 from pretreatment to the third year of litter exclusion, respectively. 4. Downstream, fine particulate organic matter on artificial substrata decreased during litter exclusion, and there was a significant reduction in colonization of collector‐filterers. Total secondary production downstream of the litter exclusion declined >70%, demonstrating that downstream colonization dynamics are linked to upstream detritus inputs and processing by stream invertebrates.