Periphytic diatom community in a Mediterranean salt wedge estuary: the Ebro Estuary (NE Iberian Peninsula)

Abstract

The Ebro River discharge is themain factor controlling hydrological dynamics in the Ebro microtidal salt wedge estuary. The aim of this study was to describe the species composition of the periphytic diatom communities, and to elucidate the main environmental factors affecting them. Samples of periphytic diatoms were collected at 8 sites along the estuary in October 2007 and January 2008. The diatom community was sampled both from natural and artificial substrata.Water depth, velocity, pH, dissolved oxygen, temperature, conductivity, total chlorophyll and water chlorophyll a, total periphytic chlorophyll, dissolved nutrients (P-PO4 3–, N-NO3 –, N-NO2 –, N-NH4 +, Si-SiO4 4–), total dissolved nitrogen and total dissolved phosphorous were determined in each campaign. Altogether, more than 120 taxa of diatoms were identified. The most abundant genera were Cocconeis, Amphora, Navicula and Tabularia. The variability of the diatom community was analyzed with multivariate analysis methods. Water stratification affected diatom community in both the horizontal and the vertical gradient, according mainly to salinity, dissolved oxygen and nutrient concentration differences.