Paleolimnological records of post-glacial lake and wetland evolution from the Isthmus of Chignecto region, eastern Canada
LE3 .A278 2012
Master of Science
Earth & Environmental Sciences
The Isthmus of Chignecto on the New Brunswick - Nova Scotia border is the location of the Tantramar, Missaguash, and Amherst Marshes, which together form a large coastal wetland system that has been the focus of much ecosystem research and habitat modification even though little is known about the systems’ evolution. In this study, lithostratigraphic and chemostratigraphic lake sediment records from three lakes are used to provide a high resolution record of post-glacial environmental change for the region. Basal dates for the study lakes range from >10,000 cal. yr BP to < 4000 cal. yr BP, indicating that each lake provides a unique story on landscape and salt marsh evolution. Lake sediment stratigraphy indicates rapid fluctuations in lake productivity. Chemostratigraphic proxies indicate fluctuating salinity and oxygen levels in two of the three lakes and show that multiple saltwater incursions likely occurred. Analyses of metals indicate anomalously high pre-historic concentrations of Pb and Hg (8 ppm and 870 ppb respectively). Historic concentrations of Pb and Hg provide evidence for significant atmospheric deposition from industrialization and anthropogenic sources. Collectively, these data suggest that a sophisticated model is required to adequately explain the physical evolution of this extensive wetland system. Periods of sustained saltwater influx into freshwater systems were likely a fundamental driver of systems change. Additionally, both anthropogenic and natural disturbances of the lakes and wetlands have the potential to increase the bioavailability of contaminants. Management of these wetlands must take into account the sensitivity of the wetland system to environmental disturbance.
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