The Effect of Transplantation Depth on the Restoration Success of Gongolaria barbata (Fucales) in the Mediterranean Sea

In the Mediterranean Sea, Cystoseira sensu latu species are experiencing a severe decline, and in the last decades, many restoration attempts have been carried out to contrast such decline. Available experience suggests that the choice of the restoration site can be more important than the methodology used. As an example, episodic events, such as intense storms, can cause the loss of the transplants used for restoration attempts, hampering the long-term success of the interventions. Here, we tested the success of restoration of the macroalga Gongolaria barbata at different outplanting water depths along the Conero Riviera (Adriatic Sea, Mediterranean Sea). After growth of G. barbata individuals in mesocosms, they were transplanted at 1, 1.5, and 3 m depth. During the monitoring period ad sea (from late July to December 2023), two strong storms were recorded. The highest success in terms of survival and growth rates increased with increasing transplanting depth. This study confirmed that, even within a narrow bathymetric range, transplantation at deeper depths of the upper infralittoral zone can reduce the impact of wave energy enhancing the success of restoration interventions.