Understanding climate resilience and restoring declining habitat-forming macroalgal populations at the rear edge of their distributionResistance, Resilience and Phase Shifts

Rosa M. Chefaoui¹, Julio Arrontes², José L. Acuña², Rosa M. Viejo¹

¹Universidad Rey Juan Carlos, Spain - ²Universidad de Oviedo, Spain

In the context of current global change, the distribution of canopy-forming macroalgae is undergoing significant shifts worldwide, leading to profound impacts on marine ecosystems. These species are crucial for ecosystem functionality, and their local extinction results in simplified habitat structures and a loss of biodiversity. While these distributional changes are often attributed to global warming, the increasing influence of fish herbivory may also play a significant role. Nonetheless, marginal populations can persist in favorable sites and microhabitats shaped by local conditions, which can alter their vulnerability to herbivores or environmental parameters, particularly during emersion periods for intertidal species. Understanding the processes that govern the persistence or extinction of these species’ populations, especially at the impoverished distribution boundary, the rear edge, is essential for refining future predictions. When natural recovery is challenging, active restoration emerges as a viable solution to preserve and promote the adaptation to climate change of these valuable ecosystems.
This presentation will outline the primary objectives, methodologies, and preliminary findings from the PERSIST and InterMaRest projects. We have employed “in situ” experimentation and sampling surveys as the methodological foundation for innovative approaches in climate change research and biogeography. By measuring how physical variables and species’ vital rates vary on a small scale, we aim to establish a baseline for the ecological requirements and most suitable locations and microhabitats. Additionally, we are integrating these experiments and surveys with spatial analysis, Lidar, and thermographic imaging to comprehend the dynamics of these species under climate change. Finally, we have scaled up from herbivore exclusion cages to exclosure fences to restore macroalgae populations and assess their potential for local-scale population regeneration.