Date of Award

Winter 2010

Project Type

Dissertation

Program or Major

Natural Resources and Earth Systems Science

Degree Name

Doctor of Philosophy

First Advisor

William H McDowell

Abstract

A variety of natural and anthropogenic disturbances influence the structure and function of stream ecosystems. While past investigations have focused on the response of community indicators to stream disturbances, functional indicators may also be helpful for assessing stream ecosystem health. To date, few studies have compared the response of structural and functional indicators to ecosystem-level disturbances. I separately measured the effects of long-term acidification, a large-scale avulsion, and the individual and combined effects of physical streambed disturbance and altered refugia availability on stream structural and functional metrics.

I found that acidification was associated with changes in macroinvertebrate communities including reduced diversity and reduced Ephemeroptera abundance. 13C and 15N isotopic signatures of three macroinvertebrate families shifted away from periphyton isotopic signatures and towards isotopic signatures of allochthonous food sources at acidified sites. Whole-stream metabolism was not significantly associated with stream pH and may be less sensitive to acidification than macroinvertebrate community metrics.

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