Streamlining restoration: optimizing strategies for recovering Cystoseira sensu lato

Macroalgal forests dominated by Cystoseira sensu lato are undergoing severe range contractions due to anthropogenic and climate-induced stressors, emphasizing the need for effective restoration strategies. Assisted regeneration techniques offer sustainable solutions to mitigate biodiversity loss. This study aimed to refine ex situ recruitment methods by combining controlled-environment cultivation with suspended algaculture to improve scalability and cost-effectiveness. Specifically, we tested whether integrating a suspended algaculture stage prior to outplanting could reduce the resource-intensive mesocosm culture phase. Three experimental conditions, varying in laboratory culture and suspended aquaculture durations, were evaluated using growth metrics (e.g., percent cover and thallus length) and physiological health (e.g., photosynthetic efficiency). Results show that reducing the mesocosm phase from three to two weeks still yields satisfying outcomes and resilience in the field, whereas shortening the laboratory period to one week leads to poorer results. These findings help optimize protocols for large-scale macroalgal forest restoration.