Relationship between substrate, physico-chemical parameters and foraminiferal tests in the Doñana National Park, a Biosphere Reserve in SW Spain

A multidisciplinar analysis of sediments collected in different environments of the Doñana National Park (Guadalquivir estuary, SW Spain) provides an overview of the textural, mineralogical and physico-chemical parameters that control the distribution of benthic foraminifera in this Biosphere Reserve. These microorganisms are absent in the fine quartzitic sands that constitute the substrate of temporary ponds with brief hydroperiods located in the dune systems and spits, as well as in other ponds with low conductivities or hypersaline conditions located in the inner marshland or near the Guadalquivir river banks. Benthic foraminifera are mainly found on phyllosilicate-rich, silty-clayey substrates, where cluster analysis permits to delimitate six foraminiferal assemblages. Cluster II (Ammonia inflata + Haynesina germanica) is the dominant assemblage in the central ponds and the margins of the main channels, while cluster IV (Trochammina inflata + Entzia macrescens) is restricted to some ponds located on the high marsh and cluster VI (Ammonia beccarii + Quinqueloculina spp.) is abundant on external beaches. Tidal fluxes cause the transport of marine species both to the inner areas of the estuary and to these beaches.