Dissertations and Theses @ UNI

Award Winner

Recipient of the 1994 Outstanding Master's Thesis Award - First Place.

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Open Access Thesis


Freshwater invertebrates--Effect of insecticides on; Freshwater microbiology; Stream ecology;


Small streams and rivers draining agricultural watersheds are frequently exposed to hazardous chemicals. Unfortunately, chemical registration procedures currently do not include standardized protocols capable of predicting chemical impacts in lotic ecosystems. Three experiments were conducted utilizing artificial streams and rock-filled artificial substrates in an attempt to further standardize stream microcosm test procedures.

In the first experiment stream microcosms were used to predict the effects of a synthetic pyrethroid insecticide on riffle insect communities. Aquatic macroinvertebrates colonized on artificial substrates were placed in artificial streams and dosed in triplicate at 0.0, 0.01, 0.1, 1.0, and 10.0 ug/L fenvalerate (cyano (3-phenoxyphenyl) methyl-4- chloro-alpha-(1-methylethyl) benzeneacetate) for a 30-day period. The stream microcosms dosed at 0.1 ug/L fenvalerate exhibited significant (p ≤ 0.05) reductions in species richness and total density following the 30-day toxicity test.

Artificial substrates placed in a natural riffle area during the second experiment were randomly sampled at weekly intervals for a seven week period to determine an optimal colonization period and to compare the artificial and natural substrate communities. Riffle insect communities colonizing the artificial substrates reached species equilibrium and maximum densities by weeks one and four, respectively. Artificial substrates were selectively colonized by collector-filterers, and collector-gatherers were more abundant in the natural substrate.

The final experiment was conducted in an attempt to reduce colonization periods and collect artificial substrate communities more representative of natural riffle insect communities. Macroinvertebrates were colonized in artificial substrates, embedded and unembedded in the natural substrate, that were either uncolonized or precolonized with periphyton. Precolonized-unembedded substrates were colonized by significantly (p ≤ 0.05) greater densities than the other experimental groups on week one. Unembedded substrate were colonized by riffle insect communities functionally more similar to the natural stream community than the embedded substrates.

Year of Submission


Year of Award

1994 Award

Degree Name

Master of Arts


Department of Biology

First Advisor

Kurt Pontasch, Co-Chair, Thesis Committee


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Date Original


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