Marine forests dominated by macroalgae have experienced noticeable regression along some temperate and subpolar rocky shores and natural recoveries are usually extremely difficult, being these forests permanently replaced by less structured assemblages.

This study presents a macroalgal restoration methodology based on recruitment enhancement techniques. The results show how, using this methodology, four populations of the canopy-forming alga Cystoseira barbata were successfully restored in areas from which they had completely disappeared at least 50 years ago (Menorca, NW Mediterranean). The study compares the feasibility and costs of active macroalgal restoration by means of in situ and ex situ techniques and defines the best indicators of success in the different restoration phases.

The obtained results show that after 6 years, the densities and size structure distributions of the restored populations were similar and comparable to those of the natural reference populations.

The authors highlight that the cost-effective and successful restoration method, monitoring and success indicators proposed in their study may have applicability for other macroalgal species, especially those that produce rapidly sinking zygotes. It is concluded that recruitment enhancement should become an essential tool for preserving Cystoseira forests and their associated biodiversity.

Verdura et al. (2018) Restoration of a canopy-forming alga based on recruitment enhancement: methods and long-term success assessment. Frontiers in Plant Science 9:1832.