Date of Award

August 2017

Degree Type

Thesis

Degree Name

Master of Science

Department

Freshwater Sciences and Technology

First Advisor

Harvey A. Bootsma

Committee Members

Brenda Moraska Lafrancois, James Waples, Laodong Guo

Abstract

As the interface between the terrestrial landscape and the open lake, nearshore areas of the Great Lakes play an important role in modulating whole-lake response to inputs of nutrients and energy from the watershed. These inputs occur primarily via tributary loading, and so it is critical to understand the dynamics of river plumes and the fate of organic carbon and nutrients delivered in the plumes. To assess the influence of river plumes on the biogeochemistry and metabolism of the Lake Superior nearshore zone, the spatial and temporal distribution of turbidity, nutrients, phytoplankton, dissolved oxygen, and dissolved carbon dioxide were measured in the western arm of Lake Superior and select tributaries from June 2016 through October 2016. This study focused on the nearshore ecosystem response to a large storm even in July, showing how the nearshore zone transitioned from a highly turbid, low productivity system immediately following the storm to high phytoplankton productivity after a one-month lag. A steady decrease in surface pCO2 in the month following suggests that increased water clarity and nutrient concentration following the plume event drive nearshore primary production. The shift towards net heterotrophy immediately following the storm event appears to be more so due to decreased water clarity and associated suppressed phytoplankton primary production rather than increased biological breakdown of dissolved organic carbon.

Download

Share

COinS