Peer Review #1 of "First ex situ outplanting of the habitat-forming seaweed Cystoseira amentacea var. stricta from a restoration perspective (v0.1)"

In the Mediterranean Sea, brown algae belonging to the Cystoseira genus play a valuable role as foundation species.Due to evidences of regression/loss of the habitats of these species caused by the interplay of human and climatic disturbances, active restoration measures have been encouraged by EU regulations.In particular, nondestructive restoration techniques, which avoid the depletion of threatened species in donor populations, are strongly recommended.In the framework of the EU project ROCPOP-Life, the first ex situ outplanting experience of Cystoseira amentacea var.stricta has been implemented in the Cinque Terre Marine Protected Area (northwestern Mediterranean).A total of 400 clay tiles, hosting approximately 3 mm-long germlings of C. amentacea, were fixed to the rocky shore with screws: the tiles were monitored for the next two months by photographic sampling, and survival (presence/absence of juveniles on the tiles), cover and growth were assessed.Additional sampling was performed 6 months after tile deployment, after which an unprecedented storm surge severely affected the restoration performance.After two months, over 40% of the tiles were covered with Cystoseira juveniles, which reached approximately 8 mm in total length.The tiles that survived the storm hosted 3-6 cm-long juveniles.The high cover (> 25%), assuring moisture and shading, and the appropriate size of the juveniles, to avert micro-grazing, at time of deployment were key to the survival and growth of the outplanted juveniles, increasing the potential for restoration success.Our findings show that outplanting of midlittoral canopyforming species is a feasible approach for restoration efforts, with particular attention given to the early phases: i) laboratory culture, ii) transport, and iii) juvenile densities.These results are strongly encouraging for the implementation of restoration actions for Cystoseira amentacea on a large scale, in light of EU guidelines.