An experimental investigation aimed at validating a seagrass restoration protocol based on transplantation

Protection and restoration are crucial components of conservation strategies aimed at preserving biodiversity and ecosystem services. Here, we propose a successful protocol to restore the most important and protected Mediterranean seagrass species, Posidonia oceanica. A 52-month experiment was carried out to evaluate the feasibility of the restoration of a P. oceanica meadow damaged by the Costa Concordia shipwreck. Specifically, we investigated: i) the suitability of cuttings taken from clods of matte detached by boat anchoring and storms, as transplanting material; ii) the effects of collection and transplanting at different depths on the cuttings' survival, shoot density, and Daily Leaf Production (DLP); iii) the degradation rate of iron transplant stakes used to fix the cuttings. Cuttings taken from clods of matte displayed a considerable survival rate (75%) and shoot density increase (+ 57%), thus pointing to an effective non-destructive alternative to the use of donor meadows for restoration purposes. Cuttings transplanted at a similar depth they were collected, offered the best effectiveness, branching more (+ 90%) than cuttings transplanted either deeper or shallower. DLP highlighted the colonization-predisposition of transplanted P. oceanica, revealing higher leaf growth than natural plants over the study period. We estimated the degradation of the iron transplant stakes would lead to a seabed free from any anthropogenic artifacts within 20–24 years. This protocol could offer significant advantages over any restoration plans so far developed, including its considerable success, extensive availability of vegetal material without impacting P. oceanica meadows, and a seabed potentially characterized by natural elements only. •Posidonia oceanica can be successfully restored to accelerate the meadow recovery.•Cuttings deriving from boat anchoring are an effective non-destructive alternative.•Transplanting Posidonia at a similar depth it was collected is the best solution.•Chemo-degradable iron transplant stakes can establish a semi-natural seabed with plants only.•Case-specific plans and protection measures are needed to reach effective outcomes.