Management of beach-cast Posidonia oceanica seagrass on the island of Sardinia (Italy, Western Mediterranean)

Removal of beach-cast Posidonia oceanica seagrass litter, called "banquettes," is a common practice on Mediterranean shores to allow the recreational use of beaches. Ongoing removal practices of R oceanica banquettes were analyzed on the island of Sardinia to quantify this phenomenon on a broad scale and to evaluate the potential environmental impacts of banquette removal and dumping on the coastal zone. Data on banquette management were collected by means of a questionnaire given to the coastal municipalities and private companies in charge of beach-cleaning operations during 2004. P. oceanica banquette removal resulted in a widespread practice applied on 44 beaches (out of 116). The total removed amount for 2004 was estimated at 106,180 m(3). Heavy machines were generally used to remove banquettes. Relationships between banquette removal and beach characteristics showed that higher quantities removed resulted in low-energy beaches. The amount of sediment subtracted to the beach following removal was evaluated by analyzing sand concentration in banquettes collected at three locations. Mean sediment concentration in banquettes was 92.8 kg m(-3). This value, multiplied for the amount of banquettes removed, allowed us to evaluate the sediment subtracted from each beach between 0.5 and 1725 m(3). Furthermore, the majority (80%) of the volume removed was dumped in unauthorized areas. Following the findings of the study, some management measures are suggested in order to minimize environmental impact of banquette removal.