Title

Macroinvertebrate Bioassessment of Five Lake Whatcom, WA Tributaries

Date of Award

2002

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Environmental Science

First Advisor

Robin A. Matthews

Second Advisor

Leo R. Bodensteiner

Third Advisor

Merrill A. Peterson

Abstract

Five streams (Anderson Creek, Austin Creek, Brannian Creek, Olsen Creek, and Smith Creek) located in the eastern portion of the Lake Whatcom, WA (USA), watershed were selected for a macroinvertebrate bioassessment study. Water quality samples were collected at all sites in July 2001, September-October 2001, and February 2002 to characterize summer, fall, and winter conditions. Results of the water quality portion of this study indicated no statistically significant differences among research sites for nutrients, temperature, dissolved oxygen, pH, conductivity, turbidity, or alkalinity. There were slight differences among sites for pH and conductivity with respect to the range of values, but the differences were not statistically significant due to the low number of replicates.

Substrate composition, riparian habitat, and aspects of channel morphology were evaluated at each study stream in September-October 2001. There were no statistical differences among sites for any substrate categories, riparian habitat or channel morphology characteristics. Substrate was composed mainly of cobble, coarse gravel, and fine gravel. The riparian habitat showed slight differences in canopy cover ranges, but due to the low number of replicates at each site, the differences were not statistically significant. Generally, the sites fell into three categories: closed canopy (Brannian Creek); deciduous canopy (Anderson, Austin, and Olsen Creeks); and open canopy (Smith Creek).

Benthic macroinvertebrate samples were collected at all sites in September-October 2001 and evaluated using multiple measures of diversity and community integrity. Sites were compared using unsealed biometric criteria (raw scores) such as the number of Ephemeroptera, Plecoptera, and Trichoptera (EPT) taxa, the percentage of Cinygma, and the ratio of EPT individuals to total individuals. The Benthic Index of Biotic Integrity (B-IBI) was used to compare the Lake Whatcom tributaries with other Puget Lowlands streams. The B-IBI’s for macroinvertebrates in the Lake Whatcom watershed were relatively high compared to other streams in the Puget Lowlands indicating clean water and good macroinvertebrate habitat in the Lake Whatcom watershed.

Austin Creek and Smith Creek macroinvertebrate data indicated these streams contained relatively large amounts of organic suspended solids that could contribute to the overall productivity of Lake Whatcom. Smith Creek also showed indications of temperature stress. Anderson Creek showed signs of low habitat complexity and sedimentation.

Bootstrap sampling was used to evaluate the performance of the B-IBI and other biometric criteria. The bootstrap sampling results indicated the B-IBI performed poorly at low counts (100-500 individuals). The variance among recounts remained high and the B-IBI did not reach a stable score until 1000 or more individuals were counted. The performance of the EPT individuals to total individuals ratio showed low variance and a stable mean value at counts of 100 individuals. The EPT individuals to total individuals ratio also ranked sites in the same order as the other biometric criteria.

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