Effect of Cultivations on Aquatic Plants in Canals in Upper Egypt

Abstract

The present study investigated the mam pollutants which are produced due to agricultural activities. The effect of these pollutants, in relation to other environmental variables, on growth and distribution of submerged aquatic plant communities was examined. Two study areas (comprised 17 sites, representing eight irrigation and five drainage canals) were selected in Kom Ombo and Nasser Districts in Aswan Governorate. The study indicated that monospecific stands were mainly recorded in drainage systems, characterized by the high dry weight standing crop (DWSC), but more diverse stands (usually occurring in irrigation canals directly connected with the River Nile) had low DWSC. Pearson's correlation was carried out to test the significance of the relationship between the mean number of the species recorded and their TDWSC. The mean monthly number of species correlated with the monthly TDWSC (positively significant) in site 2 in Ganabiet Kassel irrigation canal and El-Sahel irrigation canal, (positively very highly significant) in Suars irrigation canal and in Maniha drain (negatively highly significant. Otherwise, no significant relationship was detected between the mean monthly number of species and their monthly TDWSC at the level of each site, each waterbody and the whole set of data. CCA showed that sulphates, phosphates, total hardness, total

oxidized nitrogen (factors that directly mirror the use of agrochemical), flow rate, under water light climate, depth, bicarbonates, conductivity, dissolved oxygen and chemical oxygen demand were the most important water variables affecting the aquatic macrophytes distribution. Also, canonical correspondence analysis (CCA) indicated that sulphates, phosphates, total oxidized nitrogen, ammonia (main components of fertilizers), bicarbonates, organic matter, sodium and chlorides were the most influential hydrosoil factors. The present study pointed out the ability of Potamogeton schweinfurthii, Potamogeton nodosus, Potamogeton pectinatus and Vallisenaria spiralis to survive in habitats with relatively high hydrosoil phosphates, total oxidized nitrogen and ammonia Potamogeton perfoliatus, Potamogeton pusillus and Najas minor restricted to habitats with moderate concentrations of nutrients in hydrosoil and water. Potamogeton crispus associated with sites characterized by high water phosphates and hydrosoil ammonia. Azalia filiculoides and Ceratophyllum demersum occurred in habitats of high level of organic matter and water phosphates.