Detrital breakdown and macroinvertebrate communities affected by sedimentation in a low-gradient tributary to Lake Superior

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Conference Proceeding

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Anthropogenic disturbances in watersheds can increase the erosion of fine sediments which are often deposited in low-gradient portions of streams. Increased sedimentation may alter stream ecosystem structure and function, particularly detrital breakdown. We examined invertebrate communities as well as leaf and wood breakdown rates at replicate sand and rock reaches in the Salmon Trout River (STR), a coaster brook trout stream in upper Michigan. We hypothesized that leaf breakdown rates would be lower in high sand reaches, due to reduced shredder invertebrate biomass associated with poor substrate quality. Unexpectedly, the highest red maple leaf breakdown rate (k=-0.0098) and mean shredder biomass (46.9 mg/bag) were measured in a sand reach. Leaf breakdown rates were positively related to mean litterbag shredder biomass at each site and were significantly related to mean biomass/bag of Gammarus spp. Wood breakdown rates were 2x that of leaves and were similar in sand and rock habitats within a site. Sedimentation affects biotic communities and breakdown rates of organic material in the STR, but determining the mechanism(s) (e.g. physical abrasion, microbes, resource island effect) will require additional study.

Publication Title

Society for Freshwater Science 2012 Annual Meeting