Investigating the resilience of North-East Atlantic intertidal forests to disturbance over a latitudinal gradientMacroalgal Traits

Ruby George¹, Francisco Arenas², Fraser Brough³, Thomas Burel⁴, Michael Burrows⁵, Amelia Curd⁶, Dominique Davoult⁷, Marina Dolbeth², Gabin Droual⁶, Tom Fairchild¹, Aline Migne⁷, Pippa Moore⁸, Joanne Porter⁹, Daniel Smale³

¹Swansea University, UK - ²Interdisciplinary Centre of Marine and Environmental Research, Portugal - ³Marine Biological Association of the UK, UK - ⁴University of Brest, France - ⁵Scottish Association for Marine Science, UK - ⁶Institut Français de Recherche pour l’Exploitation de la Mer, France - ⁷Sorbonne University, France - ⁸Newcastle University, UK - ⁹Heriot Watt University Orkney, UK

Foundation species, such as canopy-forming macroalgae, are vulnerable to disturbance from extreme events, with their subsequent recovery crucial to sustaining broader community diversity. However, foundation species’ capacity to recover potentially varies on large scales and may be hampered in more stressful environments towards their range limits. To explore the variation and drivers of intertidal fucoid forest resilience, we are undertaking a large-scale collaborative experiment across seven regions spanning over 20 degrees of latitude, from the warm range-edge of canopy-forming fucoids in the Iberian Peninsula, to Northern Scotland. In Spring 2023, we simultaneously disturbed experimental plots on rocky shores in each region by removing canopy-forming fucoid algae at three treatment levels. For the past 20 months we have been monitoring canopy recovery and community responses, and investigating the potential drivers of recovery including climatic conditions, grazing, competition, and rugosity. The results so far generally support our hypothesis that recovery is hindered under stressful climatic conditions. We have also found that traits of a dominant fucoid differs between regions, with more acquisitive trait values in warmer southern regions, potentially increasing both growth and disturbance vulnerability. Overall, this collaborative experiment is advancing our understanding of how resilience of intertidal forests varies on large scales, and highlights that more stressful conditions under climate change may undermine the resilience of marine ecosystems.