Presentation Abstract
Coastal ecosystems require sediment inputs of sufficient quantity and quality to maintain ecological integrity. Identification of sources and processes affecting quality and nearshore dispersal of terrestrial sediment are important considerations for successful habitat restoration and resource management. Sourcing of sediment via geochemical fingerprinting is one way to explore such processes, and appears to be a promising approach in Cascade watersheds where volcanic uplands confer distinct geochemical signatures relative to glacial and marine sediment. A sediment geochemical source-to-sink study using compositional data of the fine fraction was undertaken from the Nooksack River watershed to Bellingham and Samish Bays in March 2019 to describe dispersal of fine-grained sediment and contaminants originating from the Nooksack River, urban streams, and coastal bluffs to shallow nearshore environments (~4 m MLLW). Principal component (PC) analysis of 12 geochemical variables identified four source-indicative PCs that described 87% of variance among 61 sites. Andesitic sediment from the north and middle forks of the Nooksack River accumulated along the City of Bellingham waterfront and south to Post Point (-PC1, -PC2, +PC3), whereas ultramafic sediment from the south fork of the Nooksack River, with extremely high chromium contents, was limited to the Nooksack River Delta (+PC2). From Post Point south into Chuckanut and Samish Bays, nearshore sediment was sourced from bluffs and local streams draining the Chuckanut sandstone (+PC1). Urban creek sediment had lower Al contents (-PC4) and elevated contents of anthropogenic metals (antimony, copper, lead, zinc). These properties will be explored as indicators of the contributions of small streams to nearshore sedimentation patterns and contaminant assemblages in Bellingham Bay. Insights from sediment sourcing can help validate sediment transport models and identify watershed areas for runoff mitigation and nearshore areas most and least likely to be adverseley affected by terrestrial stressors.
Session Title
Sediment in coastal habitats: outlooks for stability and stress
Conference Track
Data Analysis, Modeling & Decision Making
Conference Name
Salish Sea Ecosystem Conference (2020 : Online)
Document Type
Event
SSEC Identifier
2020_abstractID_4395
Start Date
21-4-2020 9:00 AM
End Date
22-4-2020 4:45 PM
Genre/Form
conference proceedings; presentations (communicative events)
Subjects – Topical (LCSH)
Coastal sediments--Washington (State)--Whatcom County; Coastal zone management--Washington (State)--Whatcom County; Watersheds--Washington (State)--Whatcom County; Habitat ecology--Washington (State)--Whatcom County
Geographic Coverage
Salish Sea (B.C. and Wash.); Whatcom County (Wash.)
Rights
Copying of this document in whole or in part is allowable only for scholarly purposes. It is understood, however, that any copying or publication of this document for commercial purposes, or for financial gain, shall not be allowed without the author's written permission.
Type
Text
Language
English
Included in
Fresh Water Studies Commons, Marine Biology Commons, Natural Resources and Conservation Commons, Terrestrial and Aquatic Ecology Commons
Sediment sourcing in Cascade watersheds and nearshore dispersal of terrestrial sediment and contaminants using multivariate geochemical analysis
Coastal ecosystems require sediment inputs of sufficient quantity and quality to maintain ecological integrity. Identification of sources and processes affecting quality and nearshore dispersal of terrestrial sediment are important considerations for successful habitat restoration and resource management. Sourcing of sediment via geochemical fingerprinting is one way to explore such processes, and appears to be a promising approach in Cascade watersheds where volcanic uplands confer distinct geochemical signatures relative to glacial and marine sediment. A sediment geochemical source-to-sink study using compositional data of the fine fraction was undertaken from the Nooksack River watershed to Bellingham and Samish Bays in March 2019 to describe dispersal of fine-grained sediment and contaminants originating from the Nooksack River, urban streams, and coastal bluffs to shallow nearshore environments (~4 m MLLW). Principal component (PC) analysis of 12 geochemical variables identified four source-indicative PCs that described 87% of variance among 61 sites. Andesitic sediment from the north and middle forks of the Nooksack River accumulated along the City of Bellingham waterfront and south to Post Point (-PC1, -PC2, +PC3), whereas ultramafic sediment from the south fork of the Nooksack River, with extremely high chromium contents, was limited to the Nooksack River Delta (+PC2). From Post Point south into Chuckanut and Samish Bays, nearshore sediment was sourced from bluffs and local streams draining the Chuckanut sandstone (+PC1). Urban creek sediment had lower Al contents (-PC4) and elevated contents of anthropogenic metals (antimony, copper, lead, zinc). These properties will be explored as indicators of the contributions of small streams to nearshore sedimentation patterns and contaminant assemblages in Bellingham Bay. Insights from sediment sourcing can help validate sediment transport models and identify watershed areas for runoff mitigation and nearshore areas most and least likely to be adverseley affected by terrestrial stressors.
