Changes to shallow subtidal benthic invertebrates following Elwha River dam removal.
Presentation Abstract
Deconstruction of two dams on the Elwha River began in September 2011, resulting in large inputs to the Strait of Juan de Fuca of sediment previously entrained in reservoirs. In the long term, restoration of a natural sediment regime characterized by unimpeded sediment transport from the upper watershed to the lower river and Strait is expected. Annual surveys to assess the response of marine benthic invertebrates to these changes in sedimentation have been conducted since 2011, with some coverage back to 2009. Sites are located along 10 km of shoreline bracketing the river mouth (treatment sites) and 20 km to the east near Green Point (reference sites), and are permanently marked to allow resurveys of the same transects. Divers identify and count individuals >2.5 cm in size (any dimension), and note presence/absence for encrusting taxa. Concurrent vegetation surveys have documented large declines in kelp and other seaweeds since dam removal started. Invertebrate taxa dependent on vegetation have also declined, for example sessile jellyfish (Haliclystus) which attach to vegetation. However, most of the invertebrates surveyed (anemones, tube worms, chitons, clams, snails, crabs, shrimp, sea stars, sea cucumbers, urchins, and tunicates) have not declined to the same extent as seaweeds. Data are currently being analyzed to better evaluate abundance trends for these taxa through summer 2013.
Session Title
Session S-06F: Elwah River Restoration: Evolution of Habitats and Ecosystems During a Dam Removal Project
Conference Track
Restoration
Conference Name
Salish Sea Ecosystem Conference (2014 : Seattle, Wash.)
Document Type
Event
Start Date
1-5-2014 5:00 PM
End Date
1-5-2014 6:30 PM
Location
Room 6C
Genre/Form
conference proceedings; presentations (communicative events)
Contributing Repository
Digital content made available by University Archives, Heritage Resources, Western Libraries, Western Washington University.
Subjects – Topical (LCSH)
Dam retirement--Environmental aspects--Washington (State)--Elwha Dam; Benthos--Effect of sediments on--Washington (State)--Elwha River; Estuarine ecology--Washington (State)--Elwha River; Sediment transport--Washington (State)--Elwha River; Marine resources conservation--Washington (State)--Elwha River
Geographic Coverage
Salish Sea (B.C. and Wash.); Elwha River (Wash.); Elwha Dam (Wash.)
Rights
This resource is displayed for educational purposes only and may be subject to U.S. and international copyright laws. For more information about rights or obtaining copies of this resource, please contact University Archives, Heritage Resources, Western Libraries, Western Washington University, Bellingham, WA 98225-9103, USA (360-650-7534; heritage.resources@wwu.edu) and refer to the collection name and identifier. Any materials cited must be attributed to the Salish Sea Ecosystem Conference Records, University Archives, Heritage Resources, Western Libraries, Western Washington University.
Type
Text
Language
English
Format
application/pdf
Changes to shallow subtidal benthic invertebrates following Elwha River dam removal.
Room 6C
Deconstruction of two dams on the Elwha River began in September 2011, resulting in large inputs to the Strait of Juan de Fuca of sediment previously entrained in reservoirs. In the long term, restoration of a natural sediment regime characterized by unimpeded sediment transport from the upper watershed to the lower river and Strait is expected. Annual surveys to assess the response of marine benthic invertebrates to these changes in sedimentation have been conducted since 2011, with some coverage back to 2009. Sites are located along 10 km of shoreline bracketing the river mouth (treatment sites) and 20 km to the east near Green Point (reference sites), and are permanently marked to allow resurveys of the same transects. Divers identify and count individuals >2.5 cm in size (any dimension), and note presence/absence for encrusting taxa. Concurrent vegetation surveys have documented large declines in kelp and other seaweeds since dam removal started. Invertebrate taxa dependent on vegetation have also declined, for example sessile jellyfish (Haliclystus) which attach to vegetation. However, most of the invertebrates surveyed (anemones, tube worms, chitons, clams, snails, crabs, shrimp, sea stars, sea cucumbers, urchins, and tunicates) have not declined to the same extent as seaweeds. Data are currently being analyzed to better evaluate abundance trends for these taxa through summer 2013.
