Date of Award


Degree Type


Degree Name

Master of Science (MS)




Patricia Chow-Fraser




Human-induced degradation of coastal marshes has been relatively limited in Georgian Bay. This part ofthe Great Lakes is sparsely populated, with human activity in most areas occurring primarily in the form of diffuse recreational and cottage development. Despite this, water chemistry varies considerably within the Bay. The overall objective of this thesis was to gain an understanding of factors currently controlling water quality conditions in marshes of Georgian Bay, so that this information may be used to assess the potential impacts of continued human development.

Coastal marsh water quality variation among sub-basins of the eastern and northern coasts of Georgian Bay was assessed with data from 105 marshes in 28 quaternary watersheds visited during synoptic surveys. Road density, wetland cover, watershed size and bedrock type were determined for each sub-watershed. Analyses revealed that road density (used as an indicator of human disturbance) is currently a significant predictor of marsh water quality, showing positive relationships with nutrients and suspended solids concentrations, and a strong negative relationship with a published index of wetland water quality, the Water Quality Index (WQI). Watershed size and wetland cover also had significant (but usually weaker) relationships to some water quality variables.

To identify factors governing the chemistry of reference marshes in eastern Georgian Bay, 34 relatively pristine marshes were sampled in spring and summer of 2009, and a GIS was used to quantify catchment features. While watershed variables such as drainage slope and amount of upstream wetland influenced some water chemistry variables, drainage basin size and order were the most important factors controlling water chemistry; marshes with large, highorder watersheds contained higher concentrations of catchment-derived constituents (e.g., phosphorus, sediments, colour), suggesting that they may be more sensitive to land development that adds nutrients or promotes soil erosion in their watershed. This would be particularly apparent in spring, when watershed runoff has a larger influence on marsh water chemistry.

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