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Leaf litter decomposition and detrital communities following the removal of two large dams on the Elwha River (Washington, USA)

October 19, 2023

Large-scale dam removals provide opportunities to restore river function in the long-term and are massive disturbances to riverine ecosystems in the short-term. The removal of two dams on the Elwha River (WA, USA) between 2011 and 2014 was the largest dam removal project to be completed by that time and has since resulted in major changes to channel dynamics, river substrates, in-stream communities, and the size and shape of the river delta. To assess ecosystem function across the restored Elwha watershed, we compared leaf litter decomposition at twenty sites: 1) four tributary sites not influenced by restoration activities; 2) four river sites downstream of the upper dam (Glines Canyon Dam); 3) four river sites within the footprint of the former Aldwell Reservoir upstream of the lower dam (Elwha Dam); 4) four river sites downstream of the lower dam; and 5) four lentic sites in the newly developing Elwha delta. Three major findings emerged: 1) decomposition rates differed among sections of the Elwha watershed, with slowest decomposition rates at the delta sites and fastest decomposition rates just downstream of the upper dam; 2) aquatic macroinvertebrate communities establishing in leaf litterbags differed significantly among sections of the Elwha watershed; and 3) aquatic fungal communities growing on leaf litter differed significantly among sections. Aquatic macroinvertebrate and fungal diversity were sensitive to differences in canopy cover, water chemistry, and river bottom sediments across sites, with a stronger relationship to elevation for aquatic macroinvertebrates. As the Elwha River undergoes recovery following the massive sediment flows associated with dam removal, we expect to see changes in leaf litter processing dynamics and shifts in litter-dependent decomposer communities (both fungal and invertebrate) involved in this key ecosystem process.

Publication Year 2023
Title Leaf litter decomposition and detrital communities following the removal of two large dams on the Elwha River (Washington, USA)
DOI 10.3389/fevo.2023.1231689
Authors Carri J. LeRoy, Sarah A. Morley, Jeffrey J. Duda, Alex A. Zinck, Paris J. Lamoureux, Cameron Pennell, Ali Bailey, Caitlyn Oswell, Mary Silva, Brandy K. Kamakawiwo’ole, Sorrel Hartford, Jacqueline Van Der Hout, Roger Peters, Rebecca Mahan, Justin Stapleton, Rachelle Carina Johnson, Melissa M. Foley
Publication Type Article
Publication Subtype Journal Article
Series Title Frontiers of Ecology and Evolution
Index ID 70249692
Record Source USGS Publications Warehouse
USGS Organization Western Fisheries Research Center