Date of Award

2017

Degree Type

Thesis

Degree Name

M.Sc.

Department

Great Lakes Institute for Environmental Research

First Advisor

Haffner, G.Douglas

Second Advisor

Paterson, Gordon

Keywords

bioaccumulation, energy density, Hg, Lake Huron, lower food web, PCB

Rights

CC BY-NC-ND 4.0

Abstract

This study investigated Lake Huron’s lower pelagic food web for regional heterogeneity using contaminant and energy dynamics. Recently, Lake Huron experienced a regime shift which has been characterized by changes in species dominance, reduced abundances, and top predator energy dynamics. The upper trophic levels of the offshore food web have been well investigated and as such, this study focused on the primary consumers (zooplankton, Mysis, Dreissenid mussels) and secondary consumers (Coregonus hoyi, Osmerus mordax, Neogobius melanostomus). Due to the well studied nature of polychlorinated biphenyls (PCBs) and mercury (Hg) in aquatic systems, these were utilized in this study as tracers to investigate trophic level dynamics and regional variability among Lake Huron’s three basins. Gut content data and stable isotope analysis were also used as a means of examining foraging behaviour. Additionally, the condition of the lower trophic level organisms was investigated using lipid content and energy density. Primary consumers revealed strong homogeneity in trophic level, PCB and Hg contents, and energy densities among and within basins of Lake Huron. However, secondary consumers revealed strong differences in energy densities, PCB and Hg accumulation patterns, and trophic levels among and within basins. Isotope data demonstrated nearshore tracking of resources in the North Channel, while both PCB and Hg data revealed high variability in bioaccumulation dynamics among the basins. This research concluded that the trophic shift in Lake Huron is primarily a bottom up process but ecological responses vary among the basins.

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