EFFECTIVENESS OF A POSIDONIA OCEANICA (L.) DELILE TRANSPLANTATION IN THE GULF OF TIGULLIO (LIGURIAN SEA) 23 YEARS LATER

Abstract

Posidonia oceanica meadows represent a emblematic marine ecosystem in both scientific and conservation contexts. Despite several national regulations and European directives promoting their protection, P. oceanica meadows have suffered an alarming decline in the last century due to increasing anthropogenic pressure along the coasts throughout the Mediterranean basin. In order to mitigate the impacts resulting from anthropogenic activities and encourage the natural process of recolonization, several P. oceanica seagrass restoration projects have been developed that involve the reforestation of degraded and restricted areas of the seabed. To date, however, in the absence of a standardized methodology, transplanting techniques, although in continuous development, are still not very effective when compared to terrestrial reforestation techniques. This study evaluated the efficacy and success of one of the first experimental transplantation attempts carried out on P. oceanica in the Ligurian Sea in 1996, on the seabed of the Rapallo marina. The reforested meadow area was again monitored in 2019 and mapped through the polygon technique by means of metric ropes; the density of leaf bundles per m² was also measured. A map of the transplanted area was produced with a GIS platform that allowed calculation of the area covered in m² and an estimate of the total number of shoots in the transplanted area, to be compared with the density data recorded in 1996. Twenty-three years later, the reforested portion of the meadow is still present and alive and is expanding, with an area that has almost doubled. The density of shoots, which has increased fivefold since 1996, confirms the good health and success of the experimental transplanting intervention. The results obtained are quite unexpected considering the high level of anthropogenic pressures acting on the transplant area, which is located within a marina. Moreover, this intervention is a unique case as there is no documented information of successful transplantation on such a long time scale in the literature.