Ecology of salt marshes in Maritime Canada: Geographical differences in species interactions and ecosystem restoration dynamics

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University of New Brunswick


Salt marshes, productive and important ecosystems, represent a large proportion of coastline in Maritime Canada (particularly in the Bay of Fundy and the southern Gulf of St. Lawrence), despite historic losses. Despite the large landmass, salt marsh ecology is understudied in our area. However, knowledge about salt marshes elsewhere may not be fully applicable to their ecology and restoration in our north temperate region. A better understanding of the geographic variation allows for improved management of salt marshes, which confer substantial ecosystem services to surrounding areas. Recently in Maritime Canada, restoration of salt marsh ecosystem functioning has become popular amongst managers to reduce lifetime (implementation and maintenance) infrastructure costs. My research investigated two salt marsh related topics at north temperate latitudes, (i) the mutualist relationship between two notable salt marsh species near their northern range limit (Chapters 2 and 3) and (ii) recovery trajectory of salt marshes exposed to high tidal, wave and winter disturbance (Chapter 4). For the former, I assessed the strength of the relationship between Spartina alterniflora (saltwater cordgrass) and Geukensia demissa (ribbed mussels) in Maritime Canada using sampling and manipulative experiments. Spartina alterniflora and G. demissa were found to co-exist in the Northumberland Strait; however, G. demissa has lower densities than in marshes in the mid and southeastern USA. The mutualistic relationship between these species was limited in Maritime Canada, but might be useful in possible future salt marsh restorations in the Northumberland Strait. For the latter, I examined a restoration assessment technique, bounds of expectation, for Bay of Fundy salt marshes, while quantifying their early successional dynamics. I provided guidance for acceptable expectations in an environment with high sediment dynamics. Overall, my research contributes to enhanced knowledge of salt marsh ecosystems in Maritime Canada, including their restoration potential, and supported several ongoing ecological and restoration salt marsh projects.