The Orbetello lagoon is located in southern Tuscany (Italian West Coast), between 42°25’28” and 42°28’57” lat. North and between 11°10’6” and 11°16’45” long. East, and covers a total area of 25.25 km. This lagoon consists of two communicating basins known as Ponente (West) and Levante (East) measuring in area respectively 15.25 and 10.00 km (values according to Travaglia & Lorenzini, 1985, modified as a result of recent filling operations), with an average depth of about 1 m. The tidal range is small and varies between 0.1 and 0.45m. Precipitation is estimated 700 mm/y (Referred to catchment basin estimated 35 Km). Orbetello lagoon receives freshwater input from Albegna river, which has 1m annual average flow-rate, with the highest flow- rates in autumn. Over the past thirty years, the Orbetello Lagoon, as many other coastal environment in the world has developed a considerable seaweed (macroalgae) proliferation (see Lenzi, 1992 and Bombelli & Lenzi, 1996, for a detailed review).