Document Type

Thesis

Degree Name

Master of Science (MSc)

Department

Biology

Program Name/Specialization

Integrative Biology

Faculty/School

Faculty of Science

First Advisor

Dr. Joseph Culp

Advisor Role

Supervisor

Second Advisor

Dr. Jordan Musetta-Lambert

Advisor Role

Co-supervisor

Abstract

North American beavers (Castor Canadensis) are expanding their range into the Arctic tundra as climate change drives earlier ice and snowmelt, and increased shrub cover. As ecosystem engineers, beavers build dams that alter water chemistry by creating impoundments within streams, trapping sediment and organic matter, and modifying nutrient cycling. This thesis evaluates how beaver impoundments interact with natural geomorphic variation in tundra streams and how impoundments affect tundra freshwater ecosystems in the western Canadian Arctic.

In Chapter 2, I compared water chemistry and benthic macroinvertebrate (BMI) community composition across 16 stream reaches, including those with and without beaver dams, with gravel and sand substrates. Sand-dominated streams exhibited significantly higher dissolved organic carbon and mercury concentrations and supported a higher relative abundance of disturbance-tolerant BMI taxa compared to gravel-dominated sites. Beaver-impacted sites had higher downstream mercury concentrations, but did not affect BMI community composition. In Chapter 3, I used stable isotope analysis to derive Layman metrics of food web structure across 15 streams. Gravel streams showed broader trophic diversity and higher niche overlap compared to sand sites. Beaver impoundments had minimal influence on any food web metric. Together, these findings demonstrate that physical stream characteristics have a greater influence on water chemistry, BMI communities and food web structure compared to beaver impoundments. By highlighting geomorphology as a key driver of benthic invertebrate communities and food web structure, this work informs monitoring and stewardship efforts in the Inuvialuit Settlement Region, where healthy stream ecosystems support food and water security, and cultural well-being under rapid environmental change.

Convocation Year

2025

Convocation Season

Fall

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