The effect of ice regimes on intertidal benthic communities in the St. Lawrence Lower Estuary

Supervisor : Mathieu Cusson (UQAC)

Co-supervisor : Christian Nozais (UQAR)

Coastal ecosystems play an essential role in regulating carbon, stabilizing sediments and supporting numerous species, through their ecological and biogeochemical functions for many habitats, but they are particularly vulnerable to the effects of climate change. In the subarctic, decreasing sea ice cover is altering the forces that structure communities in these habitats, and modifying the distribution of species. However, the impact of these changes on intertidal benthic communities remains insufficiently explored. 

The aim of this study is to assess the influence of coastal ice regimes on the abundance and diversity of mid-tidal benthic communities in eelgrass, macroalgal and mussel bed habitats in the subarctic marine St. Lawrence. 

In the absence of a protective ice foot, eelgrass beds and mussel beds are expected to decrease in size or fragment after winter, accompanied by changes in the abundance, richness and diversity structure of benthic communities. A decrease in macroalgal cover is also expected in areas exposed (intra- and intersite) to ice abrasion. My study should highlight that a change in the coastal ice regime can intensify abrasion of intertidal benthic communities that are not protected by feet of ice, with consequences for the resilience of these ecosystems.