Impact of pollution on productivity and fisheries of Lake Mariut, Egypt

Abstract

Water quality profile of Lake Mariut (Egypt) was investigated during the period from April 1996 to March 1997. A comparison of nutrient and oxygen concentrations during late 1950's with those of the present study, indicated a pattern of increasing eutrophication and organic pollution and dominance of the sewage, industrial and agricultural drains on the ecology of the lake. In the polluted main basin, the water showed much higher concentrations of some heavy metals such as iron, copper and zinc. Accumulation levels of heavy metals in fish muscles are within the legal limits of WHO standards. In response to the heavy pollution, the primary production and fertility of the main basin of the lake reduced to about 1/3 of that found in 1961. The average annual fish production declined from 1850 kg ha-1 in 1970's to only 461 kg ha-1 in 1996, and more declining is expected in the near future, unless a management programme is applied to conserve this vital ecosystem.