Metal mobility and retention associated with salt water inundation at Laytons Lake, Nova Scotia
LE3 .A278 2018
Bachelor of Science
Earth & Environmental Sciences
Sediments in wetlands and lakes have the potential to retain metals that have been mobilized by natural and anthropogenic disturbance. The role of variable water column chemistry and nutrient loads on metal retention and mobility in wetland and lake sediments is not well understood. Laytons Lake is a coastal freshwater lake located in the Amherst Point Migratory Bird Sanctuary in Nova Scotia, Canada. It experienced a series of marine inundations from the Bay of Fundy in the 1940s. In the late 1970s, researchers identified that the lake was density stratified and incompletely mixed (meromictic), which resulted in a strong chemocline and elevated conductivity levels within 3m of lake bottom sediments. A detailed paleolimnological assessment was undertaken to investigate the geochemical impact of meromixis on lake bottom sediment geochemistry, and the rate of transition from a meromictic to an intermixing state. A geochemical analysis of lake bottom sediments was accomplished by measuring total C, N and stable isotopes (δ15N, and δ13C), and using pXRF to measure elemental proxies. A total Pb curve was used to date the sediment coretemporally. It appears that Laytons Lake is no longer density stratified. A distinct chemoclineno longer exists, as only a small concentration of conductivity (1012 μScm) was detected at the bottom of the deep basin. Data from this study suggests that the lake recovered rapidly from the marine inundation and that meromixis had a very limited effect on the bulk geochemistry of the sediment archive. C/N ratios suggest that the organic matter found in the lake bottom sediment is largely from terrestrial source. This study demonstrated that in a macrotidal environment, the water and sediment chemistry of low-lying coastal lakes may be much more variable and dynamic than lakes situated farther inland, away from occasional marine inundation.
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