This work was carried out to shed light on the present status of the Burullus Lagoon's phytoplankton and the long-term changes that had resulted from phytoplankton abundance, community structure, dominant species and diversity indices. Phytoplankton dynamics were examined seasonally from summer 2013 to spring 2014 at twelve sampling stations represented by three basins (eastern, middle and western). Water was alkaline, well oxygenated and with an annual average salinity of 3.89 PSU. Nutrient concentrations were generally high. A total of 163 taxa from five classes were recorded; diatoms were the most diversified group. The three dominant classes: Chlorophyceae, Bacillariophyceae and Cyanobacteria had a progressively lower abundance from west to east, while species diversity showed the opposite trend. The results showed that Chlorophyceae was the dominant group in the three basins, followed by Bacillariophyceae in the eastern and western basins, while Cyanobacteria followed chlorophytes in the middle basin. Shannon-Wiener diversity index values were higher than those recorded during the previous years. Notable phytoplankton species recorded can be regarded as possible indicators for each basin. Providing evidence that phytoplankton abundance decreased from year to year and that a nuisance species such as Geitlerinema amphibium was evidently environmentally harmful, hence suggesting that a major improvement in water quality must be done.
Key words: Phytoplankton, Species Indicators, Burullus Lagoon, Diversity Index
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