ABSTRACT
Burullus, Edku, Manzalah, and Maryut are four large (50 to 500 km2), shallow (~1 m deep) lagoons on Egypt’s Nile Delta that intercept great amounts of agricultural drainage, sewage, and industrial effluents before they are discharged to the oligotrophic eastern Mediterranean Sea. The lagoons have been rapidly decreasing in size as fish pond aquaculture, agriculture, and urbanization encroach on them. Following the completion of the Aswan High Dam on the Nile River in 1965, Egypt’s freshwater resources became fully regulated and the intensity of agricultural irrigation and synthetic fertilizer consumption increased, leading to a rise in the amount of agricultural drainage received by the lagoons. These factors, combined with increases in upstream population and improvements in sewerage infrastructure, have had significant and often dramatic ecological effects. Salinity, as well as ecological indicators like Secchi depth (representing turbidity levels) and dissolved oxygen, have decreased over time while nutrient concentrations, particularly inorganic nitrogen, have been increasing. Commercial fish landings in Burullus, Edku, and Manzalah lagoons have been rising since the 1960s and today constitute almost half of Egypt’s national fish catch. In the most altered and industrialized lagoon, Maryut, the fishery collapsed by around 1980, when sewage from the city of Alexandria was first collected and discharged to the lagoon’s main basin. Nutrient concentrations
Abstract .......................................................................................................................................... 253 11.1 Introduction .........................................................................................................................254 11.2 The Nile Delta ..................................................................................................................... 255 11.3 Physical, Chemical, and Biological Characteristics of the Delta Lagoons ......................... 257
11.3.1 Burullus ................................................................................................................... 258 11.3.2 Edku ........................................................................................................................260 11.3.3 Manzalah ................................................................................................................. 262 11.3.4 Maryut .....................................................................................................................266
