Restoration of animal forests: a novel transplantion method for coastal octocorals in the NE Atlantic

Octocorals are among the main habitat-engineering species, generating complex three-dimensional ecosystems of unquestioned importance. Despite their importance, octocoral habitats have dramatically declined in the last decades due to several stressors. Consequently, octocoral gardens are internationally recognized as Vulnerable Marine Ecosystems. In the last decade, several octocoral restoration methodologies were the object of study, yet long-term success was sparsely achieved or lacked assessment. To reverse the actual scenario, it is important to develop cost-efficient methodologies to recover impacted, endangered octocoral habitats. In this 4-year study, we developed and tested the Direct Substrate Attachment (DSA) method. This novel octocoral transplant method was trialed with two size classes of the species Paramuricea grayi and extended with a third class (20-40 cm) using Leptogorgia sarmentosa. With a recorded 95% attachment success, yearly annual positive growth, and a survival of 75% after 4 years, we prove the suitability of the DSA methodology in habitat restoration. Moreover, transplant size did not influence success; all transplants had verifiable holdfast and growth rates of up to 8.34 +/- 1.7 cm. Seasonal growth and health status were monitored and compared to further assess the success of the transplant. The transplant performed with the DSA method is to date the first successful octocoral transplant in the Atlantic temperate seas with proven long-term success. The results achieved are especially important in a moment where ecological degradation and mitigation efforts are a hot topic among decision-makers. Using the DSA methodology, octocoral transplantation is possible and should be considered in conservation and restoration efforts.