Sedimentological and geomorphological consequences of Posidonia oceanica banquette removal: example of Sakarun Beach

Dugogodišnja praksa uklanjanja naslaga (banketa) morske cvjetnice Posidonia oceanica na plaži Sakarun u prestanku je 2020. godine zbog pojačane erozije sedimenta. Ostavljanje banketa na plaži otvorilo je priliku za proučavanje morfologije i dinamike banketa i sedimenta, kao i procjenu posljedica njihovog uklanjanja s plaže. Kroz pet jesenskih i zimskih mjeseci praćene su promjene količine istaložene posidonije i njena interakcija sa sedimentom. Na mjesečnoj bazi su uzorkovani uzorci iz 1/16 m3 naslaga posidonije radi utvrđivanja količine zarobljenog sedimenta. Za karakterizaciju taložnog okoliša i definiranja njegovih geoloških i sedimentoloških parametara sakupljeni su uzorci sedimenta plaže, plitkog podmorja i okolnih stijena. Napravljena je procjena količine sedimenta koja nestaje s plaže zajedno s uklonjenom posidonijom, te je prikazan utjecaj livada posidonije u moru i njenih banketa na obali na ukupni budžet sedimenta na plažiThe Long-term practice of seagrass deposits (banquettes) of Posidonia oceanica removal from the Sakarun beach has come to an end in 2020 due to the increased sediment erosion. Leaving banquettes on the beach provided an opportunity to study the morphology and dynamics of the banquettes, as well as the impact of their removal from the beach. During the five autumn and winter months changes in seagrass debris quantity have been monitored, as well as its interaction with sediment. In total, 1/16 m3 of banquettes was sampled on monthly basis in order to determine the quantity of sediment caught within the seagrass deposits. Samples of beach and submarine sediment together with nearby rocks were collected in order to characterize the depositional environment and to determine its geological and sedimentological parameters. Quantities of sediment removed together with banquettes were assessed, and the effect of banquettes and seagrass meadow of Posidonia oceanica on the total sediment budget was given