Seagrass meadows are very productive ecosystems and many animal species are dependent of these meadows, including a wide diversity of invertebrates. This study aims to explore spatial diversity patterns of benthic invertebrates associated to Zostera noltei Hornemann, 1832 meadows. Three meadows (A, B, C) were sampled along the salinity gradient of Ria de Aveiro. At each meadow two sites were selected and four core were taken at each site. Fauna was sorted, counted and identified to the lowest taxonomical level. ANOVA tests showed significant differences of taxa number and abundance among meadows. Highest values of species and individuals were found in meadow A (31 taxa and 3342 individuals). Lowest values of individuals were found in B (970) and lowest values of taxa in B and C (20). PERMANOVA allowed to identify significant differences among meadows, being the meadow B similar to C and both distinct from A. Simper analyses showed the main taxa responsible of the differences. These taxa included annelids (Oligochaetes, Hediste diversicolor (O.F. Müller, 1776) and Notomastus latericeus Sars, 1851), molluscs (Peringia ulvae (Pennant, 1777) and Scrobicularia plana (da Costa, 1778)), crustaceans (Cyathura carinata (Krøyer, 1847)) and nematodes. It was also observed that some annelids as N. latericeus and oligochaete and the gastropod P. ulvae presented density gradient of abundance along the lagoon from the inner side to the outer.

Acknowledgements: This research was developed under Project No. 029818, co-financed by COMPETE 2020, Portugal 2020 and the European Union through the ERDF, and by FCT through national funds.