LE3 .A278 2020

2020

Spooner, Ian

Acadia University

Bachelor of Science

Honours

Environmental Science

Earth & Environmental Sciences

The discovery in 2018 of a strontium anomaly in a fluvial lake sediment gravity core taken on the Avon River, Nova Scotia, has led to the hypothesis that strontium may be a proxy for anadromous fish movement into freshwater environments. Alewife (Alosa pseudoharengus) are an anadromous fish species known to bioaccumulate Sr while they inhabit marine environments. Alewife were thought to have migrated up the Avon River to Mantletree Lake before the watercourse was altered by hydroelectric development. The 2018 study indicated that Sr concentrations in the fluvial lake sediment core declined after the installation of the Forks River dam in 1929 that impeded fish passage. Those results suggested that Sr is transferred by alewife to freshwater environments and thus serves as a proxy indicator of marine derived nutrient transfer to freshwater environments. To test this hypothesis, two gravity cores were obtained from Mantletree Lake, a lake that was located at the headwaters of the Avon River prior to dam installation. X-ray fluorescence was conducted to determine metal concentrations in the Mantletree Lake sediment core; bankside sediment samples were used to determine geogenic Sr concentrations in soils that might have become available upon flooding. Our study determined that atmospheric lead is an effective time-stratigraphic indicator that can be used to provide adequate dating control for the sediment core from 1920 to Present. Variability in the metal data (Ti, Rb, K) indicates that flooding in Mantletree Lake associated with damming produced considerable bankside erosion and watershed disruption. The C,N and stable isotope data reflect the creation of a new active shoreline and the transfer of terrestrial organic matter into the lake basin. δ15N and δ13C trends are consistent with increased autochthonous productivity after dam installation. The strontium data are equivocal but do not appear to show a strong trend associated with the potential cessation of alewife visitation.

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https://scholar.acadiau.ca/islandora/object/theses:3402