Macroinvertebrate community dynamics: strong negative response to salmon redd construction and weak response to salmon-derived nutrient uptake

AbstractDensely spawning salmon (Oncorhynchus spp.) affect macroinvertebrates negatively through redd construction and positively through nutrients released during spawning and carcass decomposition. We investigated the long-term characteristics of this interaction by measuring density, biomass, and C and N sources in benthic macroinvertebrates over 1 y. Total macroinvertebrate community biomass decreased during spawning and redd construction. However, the percentage of macroinvertebrate biomass derived from salmon increased. The highest percentage (56%) and biomass (2.71 g/m2) of salmon-derived tissue in the macroinvertebrate community occurred 3 mo after spawning. Shredders accumulated the most salmon-derived biomass per individual; however, collector-filterers, scrapers, and predators accumulated the most salmon-derived biomass at the population level, a result that suggests multiple pathways of salmon nutrient acquisition. Salmon-derived macroinvertebrate biomass was never <22% of macroinvertebrate co...