Resilience and restoration potential of kelp forests in Nova Scotia, Eastern CanadaResistance, Resilience and Phase Shifts

Alexis Savard-Drouin¹, Anna Metaxas¹

¹Dalhousie University, Canada

Marine ecosystems are unprecedently impacted by global change, causing ecosystem distributional shifts and the emergence of alternative states. Kelp forests form some of the most productive marine ecosystems on the planet. In southwestern Nova Scotia, warming waters and invasive species have led to the defoliation of kelp forests and favor algal turf beds. With further temperature increases, other regions in Nova Scotia are expected to follow similar shifts. The Eastern Shore Islands, an area selected as a potential Marine Protected Area, is an exposed archipelago in Nova Scotia where healthy kelp forests remain. Understanding the life history characteristics that support the resilience of these kelp forests is critical, particularly under rapidly changing conditions. This research models the dynamics of kelp forests in the Eastern Shore Islands using matrix population models for the kelp species Laminaria digitata and Saccharina latissima. Through model simulations and empirical validation, we quantified life history traits most important to population resilience and the potential of both species to be restored following future declines. For both species, models showed that the successful recruitment and survival of juvenile kelp had the biggest impact on population resilience. These results align with previous research correlating the loss of available substrate for kelp recruitment to the proliferation of turf algae. Laminaria digitata is projected to be more resilient with better restoration potential than Saccharina latissima, indicating that kelp forests will further lose species diversity but remain a resilient ecosystem in Eastern Canada.