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In order to determine water quality status in the Duero basin (NW Spain),epilithic diatom samples were collected and analyzed in 137 stations in August 2004 followingnormalized standard protocols. The floristic particularities of the diatom assemblages in thebasin are discussed. A total of 429 diatom taxa were identified in the basin and 90 taxa (21%)were new for the Iberian Peninsula. Especially noticeable was the presence of Achnanthidiumrivulare, only known until now from North America. Ordination revealed the existence of fivespecies assemblages related to the following environmental factors: 5-Day BiochemicalOxygen Demand (BOD5), [PO43-], and conductivity. Light and scanning electron microscopymicrographs are provided for some common, infrequent or exotic diatom species present in theDuero basin. Three diatom indices (Specific Pollution Index SPI, European Index CEC andBiological Diatom Index BDI) were applied. All of them correlated significantly with waterphysical and chemical variables, but SPI achieved the best correlations, and is thereforerecommended as the reference diatom index for this Mediterranean basin |
