Ecological forces structuring a soft-sediment community

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University of New Brunswick


In a world undergoing rapid climate change, a greater understanding of the ecological interactions which structure our ecosystems may enable humans to predict, or even repair, anthropogenic changes upon our ecosystems. The Bay of Fundy, Canada, is an ideal system to investigate ecological interactions. Its moderate complexity of ecological factors makes it relatively easy to study, while high population densities, and replicate mudflats provide considerable investigational power. In this thesis, I explored biotic and abiotic factors that may structure the infaunal community of the intertidal mudflats in upper Bay of Fundy. I observed that winter stressors (e.g., ice presence and scour, air temperature, sediment hypoxia), as well as top-down predation, the input of resources in a system (bottom-up control), the activity of mesopredators (middle-out control), and sediment conditions were not exerting strong controlling influences upon this community. It seems likely that the infaunal community is predominantly structured by the arrival of individuals (larvae, juveniles and adults) into a site, and secondary movement (dispersal) of individuals post-settlement. Lastly, I utilized molecular scatology and next-generation sequencing to investigate the diet of one of the main top-down predators of this system, Semipalmated Sandpipers (Calidris pusilla). I observed that sandpipers were acting as generalists, foraging upon intertidal, pelagic, terrestrial, and freshwater prey items. Such a broad diet may explain why sandpiper predation was not exerting a strong controlling on the infaunal community. This diet information may alter the way we conserve this species, since current conservation efforts are directed towards beach and intertidal habitat. However, in light of the breadth of diet items observed here, conservation efforts may have to also include terrestrial and freshwater systems.