Iowa Department of Natural Resources, Geological Survey Bureau,
Technical Information Series 32, 1994, p. 111-123


M. D. Schueller(1), M. C. Hausler(2), and J. O. Kennedy(3)

(1)University of Iowa Hygienic Laboratory
University of Iowa; Oakdale Campus
Iowa City, IA 52242

(2)University of Wisconsin-LaCrosse
Biology Department
LaCrosse, WI 54602

(3)University of Iowa Hygienic Laboratory
Wallace State Office Building
Des Moines, IA 50319


The Sny Magill watershed, Clayton County, Iowa was selected for conducting a comprehensive, long term, Nonpoint Source (NPS) Pollution monitoring project. A pilot study was conducted in September and October 1991 to determine a baseline list of benthic macroinvertebrate taxa inhabiting the Sny Magill and Bloody Run creeks, and also to determine which method(s) of benthic macroinvertebrate collection would be most appropriate for future monitoring. A total of 52 taxa were identified from collections made at six sites on Sny Magill Creek and two sites on Bloody Run Creek. These 52 taxa will serve as a preliminary baseline list for the two watersheds and will be used for comparison with future macroinvertebrate collections for the NPS Monitoring Project.

A total of three sampling methods were tested during this pilot study. After careful analysis of the data collected from all three methods, the Modified Hess bottom sampler was determined to be the preferred sampling method rather than kicknets or Hester-Dendy artificial substrates. Parametric statistical tests indicated no significant difference (P=<0.05) for species richness and HBI sample means between Hess and artificial substrate samples. Coefficients of variation for replicated Hess and artificial substrate samples indicated less variability among the Hess samples. Modified Hess sampling also has practical advantages in that it is not susceptible to human disturbances and does not require a colonization period before collections.

A general evaluation of the metric data calculated from the modified Hess samples indicates that the stream reaches sampled have water quality ranging from "good" to "excellent." A similarity index was utilized to determine the degree of similarity among the eight sampling sites in the two watersheds. A definite spatial pattern of similarity among the sampling sites did not manifest itself. However, those sites which had the highest degree of similarity also possessed comparable physical and biological characteristics such as stream discharge rate, nature of substrate, and visible density of periphyton.