Honors College Thesis


Response of Stream Macroinvertebrate Community to Canopy-opening Manipulations Public Deposited

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  • Stream light availability is an important factor influencing aquatic food webs. In forested headwaters, stream algal production is often highly light-limited, so an increase in light enhances benthic algal growth, which in turn increases food availability for primary consumers in the stream. In forested headwater streams, light availability is almost entirely mediated by the canopy structure of stream-side vegetation. Over the last century, many streamside forests in the Pacific Northwest were heavily harvested, leading to dense regenerating stands along streams today. Under current conditions we hypothesize that the dense closed canopies allow for limited primary production, and investigated the reach-scale responses of benthic periphyton, stream macroinvertebrates, and prey consumption by trout to a localized release from light limitation in a paired-reach study design. We expected that increases in light availability would promote elevated algal production thereby increasing scraping invertebrate abundance, and predicted that this change in community structure would be reflected in trout diets. In contrast to our expectations, we found that the presence of a canopy gap had little influence on the invertebrate community, and this lack of change was not being masked by increased consumption of grazing invertebrates in summer trout diets.
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  • Mackaness, C. (2019). Response of stream macroinvertebrate community to canopy-opening manipulations (unpublished baccalaureate thesis). Oregon State University, Corvallis, OR.
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