Prof. Mathieu Cusson1, Caroline Susini1, Dr Stéphanie Cimon1, Prof Simon Bélanger2, Mathieu Bélisle2, Prof Pascal Bélanger2, Dr Véronique Thériault2, Prof Christian Nozais2
1Université du Québec à Chicoutimi, Chicoutimi, Canada, 2Université du Québec à Rimouski, Rimouski, Canada
In cold-temperate coastal marine systems, the ice regime plays an important role in structuring the dynamics of benthic communities. The ice foot cover may protect the underneath benthos during cold winters, while the scouring by drifting ice removes substantial biomass of the foundation species of canopy-forming macroalgae and their associated species. Since changes in ice regime is expected in the next decades, we used various rocky intertidal surveys (macroalgal growth/mortality, long-time community sampling, drone imagery) and experiments that allowed us to portray the community dynamics over a decade and estimate primary production under different ice-scouring regimes in the St. Lawrence marine systems (Quebec, Canada). Our results showed that following severe ice scour, the community resilience was fast (about two years) and was driven by the reestablishment dynamic of canopy-forming macroalgal species. By monitoring macroalgal growth and mortality, we estimated that the carbon production of undisturbed canopy-forming macroalgae could reach 1 kg•m-2•yr-1. This carbon production was reduced by 99% after a severe ice scour, but a year later values can reach nearly 0.35 kg•m-2•yr-1. Coastal assessment using aerial drone imagery allowed us to compare the macroalgal cover reduction during winter and the following summer growth. Production estimates can be extrapolated to a larger scale (> kms) as well as to define zones more at risk of scouring. With warmer winters ahead, the reduction of drifting ice rafts and ice foot cover may significantly change the dynamics of intertidal communities and their functional roles in cold-temperate ecosystems.
Presentation Slides – Mathieu Cusson
