Seasonal and spatial variation of aquatic macrophytes and phytoplankton community at El-Quanater El-Khayria River Nile, Egypt

Abstract

In this study, the phytoplankton biomass and species composition in El-Quanater El-Khayria (River Nile, Egypt) was analyzed at four sampling sites on a program of a seasonally sampling and supported by measurements of different water variables as well as biomass production of most common aquatic macrophytes. The major species of aquatic macrophytes were two submerged species (Ceratophyllum demersum and Ceratophyllum submersum), two emergent (Polygonum tomentosum and spontaneum), and one free floating aquatic macrophyte (Eichhornia crassipes). Considerable seasonal variations in water quality as well as macrophytes biomass were found in the studied areas, which result in a variation of phytoplankton flora. A total of 235 phytoplankton species belonging to 7 classes was recorded, with higher numbers in autumn and winter compared to spring and summer. The maximum number of phytoplankton (7238 × 104 L−1 cells) was recorded in winter, however, the lowest one (96 × 104 L−1 cells) recorded in spring. Chlorophyceae was the dominant group, forming 56.96% of the total phytoplankton biomass followed by Bacillariophyceae (34.82%), Cyanophyceae (7.99%), Cryptophyceae (0.10%), Dinophyceae (0.096%), Chrysophyceae (0.03%) and Euglenophyceae (0.02%). Chlorophyll a values ranged from 9.77 µg L−1 to 69.81 µg L−1, with a considerable seasonal and spatial variation. All phytoplankton classes as well as, chlorophyll a was negatively correlated with all aquatic macrophytes species except for C. submersum which correlated positively with chlorophyll a and Cyanophyceae. In addition, it was positively correlated with pH, conductivity and dissolved oxygen. Keywords: Aquatic macrophytes, Ecology, Phytoplankton, Allelopathy, Water quality, River Nile