Red Eléctrica Marine Forest

Trasplanting of the Mediterranean endemic, slow-growth seagrass Posidonia oceanica was done to promote the recovery of lost meadow at the inner part of Pollença bay, north Mallorca, Balearic Islands, Spain. The plant material used for trasplanting was plagiotropic rhizome fragments of P. oceanica produced by natural processes (storms) which were collected manually by SCUBA divers from drifting material accumulated in meadow gaps in Pollença bay. Additional planting material were seedlings obtained from fruits collected in beach cast. A total of 12800 fragments and 400 seedlings were planted manually by SCUBA divers in 2 Ha of seafloor from March 2018 to February 2020. Monitoring of the survivorship and vegetative development of trasplanted fragments and seedlings is done annually. Recovery of ecosystem function (habitat for epifauna and fish) and services (fish nursery) were also monitored. Fragment survivorship during the first 4.5 years after trasplanting was higher than 95 % while fragment size has not increased relative to initial size. Seedling survivorship was 45%. The comparison of results with previous trasplantings of plagiotropic rhizomes shows that fragment survivorship in REE Marine Forest is in the upper end of the values obtained previously while seedling survivorship is within the range of values reported previously, and similar to that shown by seedlings established through natural processes. Abundance and diversity of epifauna and fish was not different between trasplanted and control areas. The results obtained until now (September 2022) show that it is feasible to trasplant plagiotropic fragments and plant seedlings of P. oceanica when the substratum is dead matte and the location is shallow and sheltered from wave action. These results are hopeful for the success of P. oceanica restorations but preliminary because of the low growth that characterizes the species. Recovery of ecosystem function at this early stage of restoration seems minimal. Extended monitoring will be needed to assess if full recovery of structure and function is achieved and the time scales involved.