Graduate Program

Biological Sciences

Degree Name

Master of Science (MS)

Semester of Degree Completion

2007

Thesis Director

Robert Fischer

Thesis Committee Member

Charles Pederson

Thesis Committee Member

James Novak

Abstract

One of the most extreme disturbances to aquatic systems is river impoundment. Dams alter a river's ecological processes by changing the flow of water, nutrients, sediment, biota and energy. Anthropogenic flow variability can lead to changes in natural seasonal variation, which has subsequent effects on biological assemblages within the ecosystem. This study investigated the influence of extreme hydrologic events on benthic macroinvertebrate assemblages within the Sangamon River in Decatur, Illinois. Four sites were sampled from June-August 2006 using the EPA 20 jab method. Samples were processed and macroinvertebrates were identified to family or lowest identifiable taxonomic group. Primer 6.1.6 was used to describe the macroinvertebrate assemblages downstream from the impoundment, determine the magnitude required to alter benthic macroinvertebrate assemblages, and establish taxon-specific responses to hydrologic alteration. Results indicate there are site differences in macroinvertebrate assemblages, which could be attributed to taxonomic tolerances and distance from the discharge disturbance. Additionally, a discharge event >169.90 m³/sec is capable of altering macroinvertebrate assemblages, while events just over 56.63 m³/sec were not sufficient to cause an identifiable disturbance. Recolonization rates of macroinvertebrates after an extreme discharge event appear to be taxon-specific with respect to tolerance to disturbance based on sample site and date. Overall, data suggest that extreme discharge events >169.90 m³/sec reset macroinvertebrate assemblages to that of conditions before the discharge disturbance, ultimately interrupting natural seasonal variation.

Download

Included in

Biology Commons

Share

COinS