The Posidonia oceanica (L.) Delile meadow of Portovenere (gulf of La Spezia, Eastern Ligurian Sea)

The present status of the small Posidonia meadow in the Channel of Portovenere (Gulf of La Spezia, eastern Ligurian Sea) is described. Mapping was performed and the meadow and plants were investigated. Large expanses of dead "matte" widely distributed along the channel testify to an ancient meadow that is no longer present. Today the Posidonia meadow exists only on the side of the channel close to Palmaria Island. This meadow, even if it is very small, is in good condition on the western side. In the eastern part signs of a regression trend and disturbances produced by anchoring were found and were well evidenced by the coefficient AM. This parameter was developed from Giraud's coefficient A (Giraud, 1977) separating leaves broken by unknown causes. In the western part of the meadow where clean offshore waters coming through the mouth of the channel can reach the meadow, Posidonia showed a better status.