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

Geographic Coverage

Salish Sea (B.C. and 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.

Language

English

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Apr 21st, 9:00 AM Apr 22nd, 4:45 PM

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.