Date of Award:

5-2023

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Biology

Committee Chair(s)

Michelle A. Baker

Committee

Michelle A. Baker

Committee

Nancy Huntly

Committee

Charles Hawkins

Abstract

Humans have constructed canals to support agriculture, to mitigate flooding, and to discharge stormwater, especially in the Intermountain West. These canals are common in Cache Valley, where they receive flows from the Logan River during summer months. However, the ecological structure (e.g., water quality, freshwater invertebrates) and function (e.g., leaf decomposition) of these canals remains largely unknown. Studying ecosystem structure and function of these urban waterways is important because it can inform us of the health of these waterways.

My research had three objectives. First, I compared water chemistry, invertebrate assemblages, and leaf decomposition in an urban canal and the Logan River in Logan, Utah. Next, I compared these variables along a longitudinal urban gradient (i.e., from upstream reaches to downstream reaches of the waterways). Last, I examined which of the various environmental factors I measured was correlated with shredders (i.e., leafshredding invertebrates) and leaf decomposition in both waterways.

Water quality was similar between the Logan River and the canal, except for the most downstream site of the Logan River which had a higher concentration of nutrients and heavy metals. The canal had faster leaf decomposition, and facultative shredders were abundant in the canal. Facultative shredders increased with the decay rate in the canal, suggesting that these shredders are playing a critical role aiding in leaf decomposition in the canal. The most downstream sites in the canal may have had faster leaf decomposition due to facultative shredders whereas the most downstream sites in the Logan River may have had faster decomposition because of elevated concentrations of nutrients. I found that physical forces from the flow of streams (e.g., water velocity) and shredder biomass were correlated with leaf decomposition in both waterways. Total phosphorus was also correlated with shredder biomass and leaf decomposition, the latter of which is likely due to enhanced microbial activity on leaf litter.

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