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Date Permissions Signed


Date of Award


Document Type

Masters Thesis

Degree Name

Master of Science (MS)


Environmental Sciences

First Advisor

Matthews, Robin A., 1952-

Second Advisor

Bodensteiner, Leo R., 1957-

Third Advisor

Helfield, James M.


The objective of my project was to describe phytoplankton ecology in high-elevation lakes of the North Cascades, WA. I conducted my field study using a small-scale ecosystem approach encompassing four lakes in the same watershed near Mt. Baker. I used exploratory data analyses to identify spatial and seasonal patterns in phytoplankton and water chemistry. Chlorophyll-a levels were less than 2.5 μg/L, and total nitrogen and phosphorus levels were below 198 and 15.9 μg/L, respectively, indicating the low-production and nutrient-poor nature of these lakes. Chlorophyll-a was weakly correlated with total nitrogen (Kendall's tau = 0.25, p < 0.05) but was not correlated with most other water chemistry variables (p > 0.05). In the phytoplankton dataset, 88 unique taxa were found in 44 lake surface samples. The dominant taxa were members of the groups Cyanobacteria and Chlorophyta. All lakes exhibited seasonal phytoplankton succession characteristic of north temperate lakes, despite the short ice-free period. Nonparametric nonmetric cluster analysis (Riffle) resulted in separation of the four lakes into two groups based on water chemistry variables and phytoplankton abundances. The first group (Picture and Highwood Lakes) was characterized by higher water temperatures and total nitrogen levels, and lower nitrate, soluble reactive phosphate, dissolved oxygen, and pH levels compared to the second group (Upper and Lower Bagley Lakes). Higher abundances of Ochrophyta, Chlorophyta, and Cyanobacteria in the first group also contributed to cluster separation. Differences in water chemistry and phytoplankton between cluster groups could be related to differences in the lakes' external physical environments, which in turn may influence the internal chemical and biological properties of the lakes. Results from this study provide baseline information and understanding relevant to larger, longer-term research and monitoring efforts in North Cascade high-elevation lakes.




Western Washington University

OCLC Number


Digital Format


Geographic Coverage

Mount Baker Wilderness (Wash.)


Academic theses




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