The winter hyperbenthos of the Ria Formosa - a lagoon in southern Portugal- and adjacent waters

The hyperbenthic fauna of the Ria Formosa, a tidal lagoon in southern Portu gal, was sampled with a hand-pushed sledge during the winter of 1997. The h yperbenthic community in the lagoon differed from that of the adjacent sand y beaches of the Atlantic Ocean, as well as from that of the main river dis charging into the lagoon. Calculations of density, biomass and diversity re vealed higher values for the community of the lagoon. The salinity of the R ia Formosa doesn't differ from the open sea but there is a difference in ex position: the beach along the Atlantic Ocean is more exposed to currents th an the beaches inside the lagoon and that is probably the main reason why a different community is found in the open sea. A different community was al so found in the upstream part of the river which is correlated with the red uced salinity due to freshwater input.