Human-induced and eutrophication impacts on physio-chemical and isotopic water characteristics of a northeastern Nile delta lake, Egypt

الملخص EN

Deteriorated water quality of Nile Delta lakes has caused eutrophication and loss of their ecological capacity.

The study of Manzala Lake revealed that the lake water tends to evolve chemically from the south to the north towards the composition of seawater.

The lake was changed to hypereutrophic condition due to the increase of nutrient loading associated with agricultural land reclamation and urban waste disposal.

The lake water isotopic values (d18O and dD) define high evaporation rate reflecting the enrichment flux that depends on the residence time of the lake water and water turnover.

Significant variations in d13CDIC values could reflect the difference in biogeochemical conditions , degradation of organic matter, pH, photosynthesis process, dissolved oxygen and phytoplankton distribution that control such changes.

Variations of d15N-NH4 + in Manzala Lake can be transferred to microbial activities (nitrification and denitrification) assimilation of ammonium by aquatic plant, volatilization of gaseous NH3, as well as mixing with seawater.

These data are important for clarifying the present eutrophication and pollution levels of the lake, for identifying anthropogenic imprints on lake waterand also for the development of rational management plans of the lake.