Distribution of live benthic foraminifera in the Rيa de Vigo (NW Spain)

The spatial and vertical distributions of live benthic foraminifera from the muddy central axis of the Rيa de Vigo were examined under downwelling and upwelling conditions. The spatial distribution of the main benthic foraminiferal species is controlled by salinity variations (San Simَn Assemblage), food availability (Outer Rيa Assemblage) and oxygen concentrations and/or reducing microenvironmental conditions in the sediment (Inner Rيa Assemblage). crohabitat distribution of benthic foraminifera is mainly dependant on the oxygenation/redox conditions in the sediment and the vertical segregation of food. In the inner areas of the rيa, low oxygen and/or reducing microenvironmental conditions prevent the vertical segregation of microhabitats. In outer areas oxygen penetration is deep but microhabitat partitioning only occurs in the presence of additional food resources (mainly fresh organic carbon from phytoplankton blooms) which triggers the colonisation of the surface layer by new species and the migration upwards and reproduction of opportunistic species.