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Communication at the NABS Annual meeting, Keystone, 2000
(465) EVALUATION OF THE EFFECTS OF SAMPLE SIZE ON INVERTEBRATE BIOMONITORING METRICS IN AN AGRICULTURALLY IMPACTED WATERSHED IN NORTHEAST NEBRASKA.
K.D. Alexander and D.H. Dorey. Math/Science Division, Wayne State College, 1111 Main Street, Wayne, Nebraska 68787
As part of an ongoing bioassessment program, we are studying nine sites from the Willow Creek watershed, Pierce County, Nebraska using the Rapid Bioassessment Protocol adopted by the Environmental Protection Agency and the Nebraska Department of Environmental Quality. Since only minimal published information exists on the biomonitoring of streams in this region, we are attempting to determine the appropriate sample size for assessing water quality. We randomly sampled 50, 100, 150, 200 and 250 macorinvertebrates and then determined metrics for increasing sample size. Our results indicate that the Modified Hilsenhoff Biotic Index, does not change appreciably with sample size while taxa richness did not become assymptotic until approximately 200 macroinvertebrates had been sampled. Metrics involving percent dominance, ratios and EPT taxa vary with sample size in impacted sites due to the rarity of intolerant taxa.
Presented at 1:00 PM on Wednesday, May 31, 2000 in Bioassessment: Techniques
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