Macroinvertebrate Community Response To Timber Harvest And Spawning Salmon In Southeast Alaska Rainforest Streams PDF Download

This study examined the separate and interactive effects of timber harvest and salmon spawning on benthic macroinvertebrate community composition and distribution in Southeast Alaska streams. I predicted that 1) spawning salmon disturb benthic macroinvertebrate communities in riffles habitats and increase invertebrate drift, 2) the magnitude of spawning salmon disturbance is greater in highly harvested watersheds relative to less-impacted streams and, 3) that macroinvertebrates utilize refugia habitats such as backwater pools, stream edges, and the hyporheic zone during the salmon run to avoid riffle epilithic disturbances. Macroinvertebrates were collected quantitatively and qualitatively in multiple habitats during salmon runs on Prince of Wales Island, Alaska in 2007 and 2008. Spawning salmon caused significant declines in riffle macroinvertebrate density, biomass, and richness and the magnitude of this effect increased with increasing timber harvest intensity. In less-impacted streams, macroinvertebrate density and biomass increased. Macroinvertebrate density and richness significantly increased in stream drift during spawning. Stream edges and the hyporheic zone appear to offer refugia for macroinvertebrates during salmon spawning. This study demonstrated that timber harvest activities intensify the effects of spawning salmon disturbance on macroinvertebrate communities and that macroinvertebrates may utilize refugia in response to salmon disturbance and in Southeast Alaska streams.