Macroinfaunal communities in seagrass beds in Atlantic Canada: Regional variation and the effects of eutrophication and finfish aquaculture

Abstract

Seagrass beds are productive coastal ecosystems that harbour many different species of flora and fauna. The benthic macrofauna that live within the sediments perform important roles that contribute to the ecological functioning and productivity of seagrass habitats. This thesis examined variation in macroinfaunal communities associated with seagrass beds in Atlantic Canada, spatially, and locally along a gradient of human impact. Firstly, I examined the regional variation of seagrass beds and macroinfaunal communities across three provinces in eastern Canada and linked the observed infaunal variation with seagrass bed structure and environmental conditions. I found regional differences in infauna community structure, which were significantly influenced by benthic productivity (the microphytobenthos). While the microphytobenthos consistently came out as the best predictor of the infauna community, nutrient enrichment and eelgrass structure also played an underlying role. Secondly, I investigated changes in seagrass bed structure and macroinfaunal communities with respect to distance from a finfish farm. The infauna community was linked to changes in eelgrass structure, which in turn was significantly related to distance from the farm. In light of these results, I discuss the importance of large-scale spatial surveys, as well as local surveys across impact gradients, to inform the management and protection of seagrass ecosystems in Atlantic Canada.