摘要
在1965年阿斯旺高坝合龙之前,尼罗河滋养着两个沙漠--一个陆地性的,一个海洋性的.每年的洪水在提供水和富营养的沉积物以维持尼罗河河谷洪泛区和河流三角洲中生命方面的作用明显地反映在埃及农业的悠久历史[1-3]和早期的卫星图像中[4].历史上尼罗河洪水对埃及沿岸地中海的生产力的影响也许不太普遍被人们察觉到,但这种影响是引人注目的[5-7].
Prior to construction of the Aswan High Dam, the annual Nile flood delivered about 7–11 × 10^3 t of biologically available phosphorus (P), at least 7 × 10^3 t of inorganic nitrogen (N), and 110 × 10^3 t of silica (Si) to the Mediterranean coastal waters off Egypt. These nutrients stimu-lated a dramatic “Nile bloom” of diatoms which supported a productive fishery. After closure of the dam in 1965, flow from the Nile was reduced by over 90%, and the fishery collapsed. It remained unproductive for about 15 years. The fishery began a dramatic recovery during the 1980s, coincident with increasing fertilizer use, expanded agri-cultural drainage, increasing human population, and dra-matic extensions of urban water supplies and sewage collection systems. Calculations of the potential anthro-pogenic contribution of nutrients (P and N, but not Si) are consistent with the hypothesis that human sewage and agricultural drainage now support the fertility once provided by the Nile, though the nature of the productive ecosystem now supporting the fishery appears to be quite different from the historical one.
