T he effect of water quality on the phytoplankton community was investigated in Mariut wetland, Egypt. Water samples were collected from the lake through five stations representing the four basins of the lake (northeast, northwest, southeast and southwest), in addition to Nubaria canal. Eighty-nine phytoplankton species, dominated with bacillariophytes and cyanophytes, were recorded. The northwest basin had the highest number of phytoplankton followed by the northeast basin, Nubaria canal, and the southeast and southwest basins. Holoplanktons dominated over tycoplanktons, meroplanktonic, and epiphetic algae. The dendrograms resulting from the agglomerative clustering technique based on water characteristics and phytoplankton composition had more or less the same trend. Moreover, the application of principal component analysis indicated that water pH, P, Cd, Zn and HCO3
were the most effective variables affecting the distribution of phytoplanktons. Cyanophytes
were highly affected by K and salinity, while bacillariophytes were affected by water pH and
Pb, euglenophytes by Ca and Mg and chlorophytes by P, Cu and Fe. The predominance of
bacillariophytes in the lake indicates the tolerance of this group to the different pollution types,
while cyanophytes prefer fresh water and dominates the least polluted wetlands.