Restoration of soft-bottom habitats: assessing transplantation success and herbivore exclusion effects on two native seagrass species in the Eastern Mediterranean

Seagrass habitats are vital for maintaining marine biodiversity and ecosystem functions. In the Eastern Mediterranean Sea, Posidonia oceanica and Cymodocea nodosa are among the dominant seagrass species; however, these ecosystems are increasingly threatened by rising seawater temperatures, invasive herbivores, and anthropogenic pressures. Marine protected areas (MPAs) and active restoration practices have emerged as key strategies for their conservation. This study was conducted in the Gökova Bay MPA, South Aegean Sea, to evaluate the effectiveness of seagrass transplantation and the impact of invasive herbivores on restoration outcomes. Transplants were established within both open plot and exclusion cage systems to compare herbivory pressure and transplantation performance. Metrics, such as shoot density and leaf length were used to assess transplantation success, while visual surveys recorded evidence of grazing. The results revealed species-specific responses: P. oceanica showed significant variability in shoot density under different experimental conditions, whereas C. nodosa consistently declined across all treatments. Cage systems had no significant effect on the biomass performance of P. oceanica, but negatively affected C. nodosa, leading to reduced shoot density. These findings highlight the importance of tailored restoration strategies that account for species-specific ecological responses and offer preliminary insights for improving habitat conservation efforts in the region.