Seagrass biomass management
To cope with the need of the coastal authorities for precise directions on the management system for stranded biomass, the Ministry for Environment and Territory has issued the Ministerial Memorandum No. 8123/2006 (DPN/VD/2006/08123) “Management of stranded posidonia.” It reaffirms the opportunity to leave on-site deposits of stranded seagrass biomass because of their important ecological role. At the same time, it notes the possible conflict between this form of management and the use of beaches for tourism, highlighting some possible alternatives, including landfilling. According to requirements of the Ministerial Memorandum, the P.R.I.M.E. project has identified possible solutions and procedures for a proper management of stranded posidonia residues, as follows:
• On-site maintenance of banquettes: this is the best solution from the ecological point of view because banquettes protect the coast from erosion, are a trophic reserve and a source of carbon and nutrients, constitute the natural habitat for many organisms and encourage the formation of the embryonic dunes. It is possible to implement it when the presence of banquettes does not clash with tourist/bathing activities and in coastal areas where the erosive phenomenon is particularly accentuated. The choice of on-site maintenance of banquettes is desirable when the area affected by stranding is located in a marine protected area or in areas A and B of a National Park.
• Removal of stranded residues: stranded residues must be removed when it is not possible to maintain the banquettes on site because of tourist/bathing needs, incompatibility with the regular use of the coast or because of the onset of health problems. Before the removal of residues from any kind of coast (sandy or pebbly beach with dunes or vegetation, sandy and pebbly beach, rocky shore, port area), it will be necessary to remove man-made waste present in the heap. The removal operations must be done through actions aimed to preserve beaches, and using hand tools, such as rakes or shovels, or by automotive vehicles. Removal should not cause geomorphological changes to seaboard nor cause damage to vegetation. In case of removal of seagrass biomass from sandy or pebbly beach, the removal operations of stranded material from the substrate must be made so as to prevent the removal of sand or pebbles, in order to preserve coasts as a whole.
• Displacement of deposits: biomass can be stored in dry areas, transported in the backshore of the same beach where it is stored (in situ storage), moved on beaches that are not accessible or not frequented by bathers or moved on beaches that are vulnerable to erosion (ex situ storage). The displacement can be seasonal or permanent.
• Agronomic use of stranded seagrass biomass: an alternative form of treatment has been identified in the agronomic use of stranded biomass after being subject to composting. The composting process can be divided into three successive stages: 1) Mixing of materials; 2) bio-oxidation process; 3) maturation. After the removal of impurities (sieving) and final refining, the compost can be used in agriculture as a soil amendment or/and as cultivation substrate in vegetable nursery crops, upon verification of compliance with requirements imposed by the Legislative Decree No. 75/2010 “Reorganization and overhaul of regulations on fertilizers, pursuant to article 13 of Law No. 88 of 7 July 2009”: it provides for the admission of algae and marine plants in the production of compost, up to a maximum weight of 20% , after separation of the organic fraction from the possible presence of sand.
• Permanent removal and disposal in dumps of stranded seagrass biomass: the disposal in dumps is, among stranded seagrass biomass management methods, the one with the higher economic and ecological costs, so it should be performed only when none of the solutions for the management of stranded seagrass biomass described above is feasible.