Aids of the conservation of Great Lakes coastal marshes: development of a macrophyte index and a novel macrophyte sampling protocol

Croft, M.V.
M.Sc. Thesis for the Department of Biology, McMaster University


Wetlands are a valuable resource, providing many ecosystem services, but unfortunately, coastal wetlands in the Great lakes are under threat from human development, including water quality impairment, introduction of exotic invasive species as well as physical damage such as dredging, draining, and filling in of wetland habitat. These actions have a negative impact on the native flora and fauna in wetlands, making wetland conservation and important topic. Wetland macrophytes play a vital role within wetlands, not only providing food for water fowl, migratory birds, fish, and mammals, but also providing the physical structure that is necessary for fish spawning, and they provide habitat for macroinvertebrates and zoobenthos. Different macrophyte species have been found to be associated with varying water quality conditions, and because of this wetland macrophytes are useful indicators of water quality conditions. I have developed a Wetland Macrophyte Index (WMI) using 127 wetlands throughout all five Great Lakes (Chapter 1), which relates plant species presence/absence data to water quality conditions, making it a useful indicator of fish habitat. The WMI was validated using historical data from two wetlands from before and after a remedial action plan was put in place and also it was successfully applied to two Canadian National Parks. Information on the presence/absence of wetland macrophytes can be a very important tool in wetland conservation, but, unfortunately, there is no standard method for sampling macrophytes. In the second chapter I will compare two common macrophyte sampling methods (grid and transect) to a novel method (stratified) in six wetlands (three pristine and three degraded). The stratified method has proven to be beneficial for determining the macrophyte biodiversity within a wetland because more species, more unique species, and more rare species were found with the stratified method compared to the grid and transect methods.

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