Phytoplankton from NE Do?ana marshland (El Cangrejo Grande, Do?ana Natural Park, Spain)

Phytoplankton from NE Do ˜ nana marshland ("El Cangrejo Grande", Do ˜ nana Natural Park, Spain) The study area ("El Cangrejo Grande", Do˜ nana Natural Park) is located at the final section of the Guadiamar River channel and it is a part of the NE Do˜ nana marshland. The hydrological characteristics of the area are complex and dynamic due to the different origin of its water input: the Guadiamar River basin, the Guadalquivir River estuary, and rice paddies outlets. This area is included in the hydrologic regeneration plan for the Do˜ nana marshland ("Do˜ nana 2005"), though the present study was finished before any modification took place. Phytoplankton richness was high since a total of 224 phytoplankton taxa were registered. Diatoms and Clorophytes were the groups that had the highest richness, Nitzschia palea, Cyclotella atomus and Monoraphidium contortum being the most widely distributed and abundant species. Phytoplankton exhibited a strong seasonal variation, in both composition and biomass, segregated in two periods (flood and desiccation) as suggested by the results of the PCA. On the other hand, the spatial differences were less evident according to a multidimensional scaling analysis (MDS). This seasonal pattern was stronger in the ordination of physico-chemical variables (conductivity, nutrient concentration and suspended matter). We conclude that this system is an ecotone zone with a high hydrologic complexity due to a variety of water inputs with a strong seasonality. These hydrologic features would be the determining factor in phytoplankton composition and high taxon richness.