Resumen de Flood effects on algal biodivesity in a mediterranean river
Jaume Cambra Sánchez, Joan Gomà Martínez
The effect of flood event on the algal biodiversity of the Siurana river, in 10 october 1994, has been studied. The algal flora, the chemical and physical data and the diatom diversity index were compared before the perturbation with equivalent data sampled after this event. As a consequence of the flood, the physical and the chemical characteristics of the water changed, and an alteration of the phytobenthos was observed. Before the flood, the diatom comunities had been dominated by: Achnanthes affinis, Achnanthes flexella, Cymbeila perpusilia, Denticula terms. Diatoma vulgare, Fragilaria capucina, Fragilaria intermedia, Melosim varians, Navicula lanceolata and Nitzschia palea; in this case, the communities were well structurated, with a relatively high diversity index (IT: 1.8-3.7 bits). However, after the perturbation, the communities were less structurated (H'= 0.3-2.1 bits) and dominated by r-strategists as: Achnanthes ?ninutissima, Cocconeis pediculus, Epithemia sorer, Fragilaria ulna and Rhopalodia gibba. Nevertheless, nine months later, the rnacroalgae assemblages were similar to those which were before the flood. However, there is an increase of filamentous green algae (especially Cladophora glomerata and Spirogyra sp.) was observed, though the characean populations were less important.
