Recent changes of macrophytes distribution in the Orbetello lagoon (Tuscany, central Italy).

1 - In this study recent changes of the distribution of three phanerogam species (Ruppia cirrhosa, Cymodocea nodosa, and Nanozostera noltii) were studied in the Orbetello lagoon, a meso-eutrophic and human stressed ecosystem. 2 - The aim was: I) to produce SURFER distributions maps, and II) to statistically evaluate significant changes in the spatial distribution taking into account two different factors (basin and year). For these reasons, percentage of coverage (CP) of each species was estimated in 38 sites equally distributed inside the Eastern and Western basins both in summers 2003 and 2009. 3 - The geostatistical maps evidenced changes in phanerogams distribution during the studied period but only variations observed for the N. noltii species at basin level resulted significant on a statistical basis. Significant differences at basin level were also obtained by the multivariate analysis. These results might be explained by the different ecological characteristics existing between Western and Eastern basins.