Distribution and ecology of benthic foraminifera in the Santoña estuary, Spain

Resumen

The living and dead assemblages in the Santoña estuary were studied seasonally in order to determine the distribution and abundance of the benthic foraminifera in this area. Samples were collected from Winter 1983 to summer 1985 to document the seasonal variation of the faunas and various ecological factors in the intertidal zone. Salinity is thought to be the main control of the living assemblages and two different biofacies characterising the upper and lower areas have been defined. Ammonia beccarii and Haynesina germanica are the most dominant forms throughout the estuary with Miliammina fusca as co-dominant in the upper estuary and Quinqueloculina seminulum as co-dominant in the lower estuary.

The dominant living species are also dominant in the dead assemblages but in the latter the agglutinated indigenous component is much more abundant. This compositional difference is thought to be caused by production rates and change in the environmental conditions within the estuary. The living and dead assemblages have been analysed and compared using the Fisher a diversity index, Triangular plot of wall types and Sanders similarity index.