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Document Type

Thesis - University Access Only

Award Date


Degree Name

Master of Science (MS)


Wildlife and Fisheries Science

First Advisor

Walter G. Duff


In the summer of 1990, four sampling gear and four sorting techniques commonl y used in wetland invertebrate investigations were evaluated. In the summer of 1991, the impact of the insecticide phorate on wetland invertebrates, and the use of a community diversity index and electrophoresis as methods for revealing the impact of phorate were evaluated. The objectives of this study were 1) to determine which of the four sampling gears is most effective at capturing invertebrates, 2) to determine the effectiveness of the four sorting techniques, 3) to determine the influence of phorate on biological and genetic diversity in invertebrates and 4) to determine the ability of the diversity index and electrophoretic analysis to reveal the impact of phorate on invertebrates. Of the four sampling gears evaluated, two were considered active (Gerking sampler, core) and two were passive samplers (activity trap, artificial substrate). The sampling gears were rated based on the number and diversity of invertebrates captured. The Gerking sampler captured significantly (t c 4.5, P = 0.02) more invertebrates than the other three sampling gear types and also captured more taxa (13) than the activity trap (11), artificial substrate (10) or core sampler (5). Sorting techniques included two types of dye, an elutriator device, and a behavioral extraction device. The two types of dye were evaluated based on the amount of time taken to sort the respective samples. The efficiency of the elutriator and behavioral extraction devices was determined by the percentage of total invertebrates extracted from the samples. There was no significant (ttest = 0.7, P = 0.48) difference in sorting times between the Rhodamine B and Congo Red dyes, or between the sorting efficiencies of the elutriator and behavioral extraction sorting devices (Mann-Whitney U=17.5, P=0.30). Field and laboratory studies were conducted to reveal the impact of phorate on the biodiversity and genetic diversity of wetland invertebrates. For the genetic studies, amphipods (Hyallela azteca) and mayflies (Baetis spp.) were placed in constructed mesocosms in wetlands and in aquaria under laboratory conditions and were exposed to varying amounts of phorate. Invertebrates samples were genetically tested using cellulose acetate electrophoresis techniques. The FUM, PGM, IDH, MOH and GPI enzyme systems were selected for analysis. Allele and genotype frequencies were calculated for invertebrates in treatments and invertebrates from the parent population not exposed to phorate. Chi-square analysis revealed significant (X2 = 7, P = 0.00) differences in the allele frequencies between the parent populations and individuals of both species treated with phorate. In addition, there were significant (X2 = 4.8, P = 0.03) differences in the genotype frequencies between the parent populations and treatments of both species. Results indicate phorate selected against sensitive individuals of both species and electrophoresis was effective at detecting differences between controls and treatments. Separate mesocosm studies were conducted in wetlands (same wetlands as in genetic studies) to reveal the impact of phorate on invertebrate survival. Invertebrate data from control and treatment mesocosms were analyzed using the Simpson's dominance index to give a measure of species diversity. Invertebrate mortality was high in treatments, yet Os values for control and treatment mesocosms were both relatively high, indicating diversity. Also, there were no significant (X2 = 0.5, P= 0.75) differences in Os values for control and treatments. Results from Simpson's index analysis indicate this index was ineffective at revealing water quality or invertebrate community health.

Library of Congress Subject Headings

Aquatic invertebrates--Collection and preservation--Evaluation


Includes bibliographical references (pages 40-41)



Number of Pages



South Dakota State University


Copyright 1983 Mark A. Brinkman. All Rights Reserved.