Seagrass sod transplantation: A relevant tool for preventing the destruction of meadows in coastal construction projects

We present a successful case of seagrass meadow transplantation on the scale of an industrial project, challenging the long-held belief that these ecosystems are "non-transplantable." Using a sod-based transplantation technique, we relocated 384 m² of Posidonia oceanica meadow from a construction site in 24 days in 2017 to mitigate the environmental impact of reclaiming six hectares of marine land for a new development in Monaco. The eight-year monitoring program (2017–2024) evaluated both structural and physiological parameters of the transplanted seagrass, along with the sediment chemistry in its surrounding environment. Despite nearby maritime construction works during two years, the transplanted meadow showed remarkable resilience, with its health indicators quickly aligning with those of the surrounding natural meadows. Three years after transplantation, the seagrass was flowering in synchrony with the natural meadow and after eight years, its area had expanded beyond the initial transplant, growing by 25,8 % in 2024. This outcome supports salvaging and subsequent transplantation as a viable, ecologically sound alternative to destruction and subsequent compensation measures in coastal development projects. By confirming the effectiveness of careful transplantation techniques, the study underscores that transplantation should be fully considered as a relevant mitigation measure in the Avoid-Mitigate-Compensate sequence.