The Effect of Large Wood Restoration on Algal Biomass and Spatial Distribution in the Narraguagus River
Author: Kiera M. Luu
Major: Marine Sciences
Graduation Year: 2022
Thesis Advisor: Hamish Greig
Description of Publication: The Atlantic Salmon (Salmo salar) is an anadromous fish native to the eastern US and Canada. Though they used to inhabit much of the eastern coasts of New England and Canada, the last of the United States’ wild Atlantic Salmon are now mostly limited to Maine. Due to habitat destruction from dams and historic logging activity, the quality of food sources, spawning grounds, and essential juvenile salmon habitat have been severely impacted. This habitat is the rearing area for many young salmon, and its quality influences their growth and recruitment into the overall Atlantic salmon population. Restoration of Atlantic salmon in Maine typically focuses on these freshwater rearing habitats, reconnecting headwater streams to the ocean using process-based habitat restoration like the addition of large wood structures to the stream to improve habitat quality. Large wood structures utilize natural processes to trap organic detritus, redirect and alter water flow, and restore ecological processes that foster ideal spawning conditions in the riverbed. Ideally these log structures would encourage winding, meandering stream flow, provide habitat for aquatic insects, and encourage a transition from muddy and sandy substrates to the cobble beds that are ideal for salmon spawning. Ongoing research at UMaine is examining the effects of restoration techniques on insect population structures, substrate, detritus breakdown, velocity, and algal biomass. My thesis as a subset of this project tracks the progress of large wood restoration through its effect on the spatial distribution of algae across 10 test and reference sites in the upper Narraguagus river. We analyzed characteristics of the system pertaining to large wood to determine which had the greatest effect on algal biomass and distribution. We found that the null hypothesis (factors not affected directly by large wood) was the best model, and that velocity and substrate alone were statistically equivalent. This suggests that restoration status had a lesser effect on algal communities than velocity and substrate. Though we cannot conclude from our analyses that restoration impacts algal communities directly, further analyses into the impact of large wood restoration on velocity and substrate may clarify whether it is indeed helpful to algal communities or not.
Location of Publication:
URL to Thesis: https://digitalcommons.library.umaine.edu/honors/743