Influencia de la batimetría y tipo de sedimento en la distribución de la microfauna (foraminíferos bentónicos y ostrácodos) en la plataforma marina vasca

Abstract

In this work we describe the microfaunal bathymetrical distribution (foraminifers and ostracods) in the benthos of the Basque continental shelf, by studying the spatial distribution of assemblages. This distribution is controlled by environmental parameters related to depth and type-sediment. A total of 114 species of benthic foraminifers and 88 species of ostracods have been taxonomically identified. Most abundant benthic foraminifer species are Lobatula lobatula, Cibicides refulgens, Gaudryina rudis, Textularia sagittula, Cassidulina laevigata and Globocassidulina subglobosa. Most abundant ostracod species are Carinocythereis carinata, Costa edwardsii, Cytheropteron nodosum, Pterygocythereis ceratoptera and Pterygocythereis jonesii. Foraminifer and ostracod assemblages are distributed accordingly with bathymetry defining three fringes: littoral-inner shelf (<70 m), middle shelf (70-130 m) and outer shelf (>130 m). Inside these bathymetric fringes the sediment-type is the main factor of control for the relative abundance of the species, in particular the percentage of fine-grained (silt-clay) particles in the sediment. The occurrence of estuarine species in areas of the Basque shelf evidences the pattern of currents responsible of the sedimentary dynamics in this shelf