EGYPTIAN URBAN ECOSYSTEM LINKAGES BETWEEN WETLANDS VEGETATION AND TREATED WASTEWATER

摘要

This study was conducted to evaluate the existing condition of Lake Maryout inrnconsideration of various proposals to upgrade the existing wastewater treatmentrnfacilities at the East and West Treatment Plants. The vegetation composition, densityrnand biomass of the four basins of Lake Maryout were evaluated twice during 1996,rnonce in May and again in October. Lake Maryout is divided into four basins, with therneffluent from the East Treatment Plant and the West Treatment Plant both dischargingrninto the Main Basin (2,184 ha). The other three basins include the Southwest Basinrn(2,144 ha), the Northwest Basin (966 ha), and the Fishery Basin (378 ha). Thesernbasins do not receive wastewater treatment plant effluent. In addition, the distributionrnof dominant vegetative communities was evaluated from satellite imagery at two pointsrnin time, once for imagery dated April 1996 and again for imagery dated April 1991.rnPhragmites australis (Phragmites) is dominant in all four basins. No other dominantrnspecies is common in all basins. Submerged aquatic vegetation species, includingrnCeratophyllum demersum and Potomogeton pectinatus, are codominant withrnPhragmites in the other three basins. Species of submerged aquatic vegetation werernnot important in the Main Basin. The vegetation of the four basins are managed tornsome extent by fisherman, using management techniques including burning, cutting,rnplanting, and anchoring vegetation. These efforts are not expected to have had arnsignificant effect on this study.rnPhragmites biomass and density were significantly different between seasons, andrnPhragmites density was lowest in the Main Basin. No other species was dominant orrncodominant in the four basins. The results of the satellite imagery analysis indicatesrnthat the Main Basin has undergone a large community shift from 1991 to 1996, with arnloss of almost 1,000 acres of submerged aquatic vegetation. No other species orrnbasin experienced a change close to this. In addition, the Main Basin is the only basinrnwith a significant proportion of its surface in open water (36 percent).rnThese differences are attributed to the high nutrient loading, the presence of a layerrnof putrescible organic matter (sludge) averaging 8 cm in depth, and the anoxicrnconditions in the water overlying the substrate in the Main Basin. Theserncircumstances may limit the ability for a submerged rooted vascular macrophyte tornobtain sufficient oxygen for metabolic respiration. This situation would be expected tornbe reduced over time if the source of effluent is eliminated or loading is significantlyrnreduced.