Date of Award

August 2017

Degree Name

Master of Science (MS)

Department

Civil and Environmental Engineering

Advisor(s)

Charles T. Driscoll

Keywords

Adirondacks, New York, Fish removal, Lake Trout, Mercury concentrations, Smallmouth Bass, Trophic interactions

Subject Categories

Engineering

Abstract

Mercury contamination within aquatic ecosystems is a concern in the Adirondack Park of New York State due to mercury deposition from global and regional atmospheric sources coupled with watershed characteristics that drive biophysical processes which mobilize and transform mercury, increasing its bioavailability. Short-term internal biological forces also impact mercury bioaccumulation as fish communities and populations change due to species introductions and lake management practices causing alterations in food web structure and energy transfer. Little Moose Lake, located in the southwestern region of the Adirondacks, provides an opportunity to study how shifts in food web dynamics may impact biological cycling of mercury. To promote the native Lake Trout fishery in Little Moose Lake, large-scale annual removal of non-native Smallmouth Bass has been utilized as a management strategy for over 15 years. Utilizing archived tissue and otolith samples and historical data, changes in total mercury concentrations, stable carbon (δ13C) and nitrogen (δ15N) isotopes, diet, age and growth were evaluated over time for Smallmouth Bass (Micropterus dolomieu) and Lake Trout (Salvelinus namaycush), the native top-predator in Little Moose Lake. Mercury concentrations in Lake Trout have increased over the 15-year period, while Smallmouth Bass mercury concentrations decreased over the same interval. Thus, changes in mercury deposition were likely not the main driver for these observations. Diets also changed over time, with Lake Trout consuming higher trophic level prey with higher concentrations of mercury and growth for both predator species increased. Changes in stable isotope signatures were also observed for both predator fish species and several lower trophic level organisms with a tendency for both δ13C and δ15N to be more depleted over time. The annual Smallmouth Bass removal resulted in shifts in trophic transfer mechanisms that influenced the temporal mercury trends in the two top-predator species. The knowledge gained from this in-depth study will allow better understanding of spatial patterns and temporal trends in sportfish mercury concentrations in the context of food web changes.

Access

Open Access

Included in

Engineering Commons

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