Brackish-water polychaetes, good descriptors of environmental changes in space and time

1 - The aim of this study is to review the knowledge on the distribution of soft bottoms polychaete assemblage in Mediterranean brackish-waters.
2 - The Polychaete distribution of several biotopes located along the Tyrrhenian and Adriatic coast, which has been the object of authors' past studies, is reported and discussed.
3 -Polychaete species composition was used to identify patterns of distribution inside the same biotope and among different biotopes, as well as changes in time in the same biotope.
4 - Polychaetes was revealed good descriptors of biotope characteristics, reflecting a pattern similar to that arising from the examination of the entire benthic community.
5 - We propose the use of polychaete assemblage fearures in assessing the ecological quality status of brackish-water bodies. For this purpose a general model of species distribution is given.