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Date of Award

Fall 2025

Document Type

Masters Thesis

Department or Program Affiliation

Environmental Sciences

Degree Name

Master of Science (MS)

Department

Environmental Sciences

First Advisor

Strecker, Angela Lee

Second Advisor

Bunn, Andrew Godard

Third Advisor

Rawhouser, Ashley K.

Abstract

Mountain lakes provide habitat for many threatened species and are important indicators of environmental change. Mountain lakes are experiencing accelerated rates of climate change and threats to their native biota from the stocking of salmonid fishes. Mountain lake benthic macroinvertebrate (BMI) communities are an integral part of the lake and surrounding ecosystem, but can also serve as valuable indicators of environmental change. The National Park Service’s North Coast and Cascade Inventory and Monitoring Network (NCCN) conducted long-term monitoring of benthic macroinvertebrate communities in 12 mountain lakes and supplemental samples in 50 additional lakes in Mount Ranier National Park and North Cascades National Park Complex. Many of the lakes sampled have reproducing fish populations and over the study period (2008-2022), 11 mountain lakes had targeted fish removals conducted on them.

My objective was to use the NCCN data to study how mountain lake BMI communities are changing over time and how that change is influenced by climate change and fisheries management decisions. I used linear mixed effects models to test the influence of water temperature, growing period and fish status, as well as linear models to test static lake attributes on temporal beta diversity, proportional taxa gains and proportional losses. Multi-level pattern analysis was used to identify indicator taxa associated with fish absence or presence. I found the BMI communities across all long-term monitoring lakes to be experiencing a high rate of temporal beta diversity (mean 0.53 ±0.12 SD). Water temperature and growing period, as well as the status of fish in the lake (removed, absent, or present) all influenced the rate and direction of change. Higher water temperatures and longer growing periods had relationships with lower proportional losses and higher proportional gains of taxa respectively, in the following year. The presence of fish depressed proportional gains and the removal of fish increased temporal beta diversity. Lakes with larger perimeters experienced higher rates of proportional gains and lower proportional losses. Additionally, indicator taxa analysis identified three taxa associated with fish absence (Ameletidae, Desmona, Micropsectra) and eight taxa associated with fish presence (Odonata, Hirudinida, Sialis, Amphipoda, Pagastiella, Microtendipes, Cladopelma, Cryptochironomus). My findings provide a deeper understanding of mountain lake BMI community dynamics and its drivers. Additionally, my study provides insight into how fish affect certain mountain lake BMI taxa, which is useful for mountain lake and land managers.

Type

Text

Keywords

Freshwater Ecology, Benthic Macroinvertebrates, Lakes, Mountain Lakes, Limnology, Long-term Monitoring, Temporal Beta Diversity

Publisher

Western Washington University

OCLC Number

1565075076

Subject – LCSH

Freshwater ecology--Washington (State); Benthic ecology--Washington (State); Limnology--Washington (State); Climatic changes--Washington (State)

Geographic Coverage

Washington (State)

Format

application/pdf

Genre/Form

masters theses

Language

English

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.

Creative Commons License

Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 License.

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