Studies have demonstrated that the origin of eutrophication isthe huge amount of nutrients stored in the sediments (Innamoratiand Melillo, 2004; Lenzi et al., 2003) and the yearly generation ofnutrients from four fish farms located in the lagoon (Lenzi et al.,2003). The best way to decrease this concentration, according toInnamorati and Melillo (2004), is to increase the water exchange.Moreover, the lagoon has to be protected from anoxia events fol-lowing the decomposition of the huge amount of macroalgae thatbloom in spring and autumn. The amount of nutrients removedby harvesting macroalgae, however, is very small compared to thenutrients in sediments (Lenzi et al., 2003). That study seems to bethe most accurate available study on the quantity of the macroalgaespecies growing in the Orbetello Lagoon and their data have beenutilized for this paper.