Evolution of a Saline Fen near Fort McMurray, Alberta: Applications from Paleoecology to Wetland Reclamation

English Abstract:

Wetland reclamation, which is crucial for Canada’s oil sands industry, is greatly challenged by salinization. Thus, understanding the origin and development of boreal saline wetlands, the most suitable natural models for potential reclamation pathways, could be of paramount importance for enhancing wetland construction design, providing a basis for setting reclamation targets. Preliminary investigation of the evolution of a saline fen in the Fort McMurray area (56°34'28.84" N, 111°16'38.39" W) confirms the usefulness of paleoecological data for the creation of wetland reclamation strategy. Variations in physicochemical properties and microfossil (pollen, non-pollen palynomorphs, and diatom) assemblages in pond sediment cores demonstrate paleoenvironmental changes associated with the saline fen initiation and its further development. The transition from clay sediments, characterized by low concentration of microfossils, to gyttja indicates that the drainage of large and deep proglacial Lake McMurray preceded the fen establishment. Further detailed studies of primary succession that took place at that time can provide a framework for the transformation of mineral tailings lacking vegetation, into peatlands tolerant of saline conditions. Upcore shifts in microfossil assemblages reflect change in salinity suggesting the existence of periods of higher salinity (recorded by a dominance of brackish diatoms) followed by period of decreased salinity (indicted by a rise in freshwater species) with gradual increases in salinity thereafter. In-depth paleoecological research should help to identify natural drivers of salinity variation that can be used to reduce salinity at contracted wetlands; on the other hand, assessment of temporal changes in ecosystem functioning associated with differences in level of dissolved salts may lead to different reclamation approaches capable of dealing with the higher salinity conditions.