Seasonal changes of phytoplankton in three coastal lagoons of the Ebro Delta in relation to environmental factors

Seasonal changes in phytoplankton cell numbers and species composition were studied in three coastal lagoons of the Ebro delta (Encanyissada, Tancada, Buda) from May, 1978 to May, 1979 in relation to salt concentration, nutrients and other environmental factors. Species composition, abundance and seasonal distribution of the phytoplankton during the year depend mainly on salinity changes produced by the balance between fresh and salt water inflows, and also on the nutrient concentration which is related to the freshwater inflows. If the water circulation between the lagoons and the sea is restricted, the lagoon changes to a high eutrophic state, with the gross development of the phytoplankton that takes the lead over the phytobenthos.