Degree Type


Date of Award


Degree Name

Doctor of Philosophy


Animal Ecology

First Advisor

Roger W. Bachmann


The ecological structure and functioning of agriculturally impacted streams, as relates to carbon dynamics, as well as the functional relationships of the invertebrate community to their food source, is unknown. The purpose of this study at Big Creek, Iowa, was to quantify the annual flow of carbon through its various compartments and to relate these carbon sources to the structuring of the invertebrate community in this second order, agriculturally impacted stream. We have compared our findings to the various predictions of the River Continuum Concept, especially as they may relate to the idea of a "reset mechanism" within the continuum;Dissolved organic matter (fraction 0.45 u) makes up 9% and the coarse particulate matter (fraction > 1mm) is 1% of the total;Gross primary production, was about 19 kg day[superscript]-1, equivalent to 1% of the allochthonous organic inputs, while ecosystem respiration was 35 kg day[superscript]-1 or equivalent to about 2% of the allochthonous input;Of the daily terrestrial production of 48,528 kg C day[superscript]-1, 4% or 1851 kg C day[superscript]-1 is allochthonous inputs to upper Big Creek of which 99% is transported out of the upper section. This follows the idea of a reset mechanism within the River Continuum Concept, i.e., that a low order stream, with a disturbed riparian zone, will have similar biological, chemical and physical characteristics as a medium sized undisturbed stream;The invertebrate functional groups in Big Creek also show many of the characteristics predicted for a middle sized stream. Though the shredder component is present, composing 18% of the total biomass, they do not dominate the biomass of Big Creek as predicted by the River Continuum Concept for low order streams. The biomass at Big Creek is dominated by the collectors with 37% of the total. The predators at Big Creek show a surprisingly high biomass at 31%. The biomass of the scrapers is 14%.



Digital Repository @ Iowa State University,

Copyright Owner

Thomas Edward Robertson



Proquest ID


File Format


File Size

165 pages