Effect of Domestic Pollution on the Distribution of Nitrogenous and Phosphorus Species in the Coastal Mediterranean Region in front of the Eastern Harbor of Alexandria, Egypt

The coastal Mediterranean region in front of Alexandria is subjected to water exchanges with Eastern Harbor throughout El-Boughaz and El-Silselah openings. Surface and bottom water samples were collected seasonally from this area to investigate the influence of discharged domestic wastes on the levels of nitrogenous and phosphorus species. The extensive waste discharges, mainly from Kayet Bay outfall, increased dissolved inorganic phosphorus (DIP), dissolved organic phosphorus (DOP) and particulate phosphorus (PP), especially at the near shore locations. However, the regression equations of DOP with salinity and of PP with suspended particles indicate that DOP and PP might also be associated with biological activities. The ratio of DIP/DOP indicates predominance of DOP. The maximum nitrate and nitrite averages near El-Silselah outfall reflect their high contents in its discharges. The regression equations versus salinity indicate that nitrate was mainly derived from this outfall, which was not the only contributor of nitrite. Abundance of ammonium was similar to that of nitrate. The annual mean surface nitrite, nitrate and ammonium concentrations were higher than the bottom means, reflecting the direct influence of discharged wastes. The maximum surface and bottom dissolved organic nitrogen (DON) averages in front of El-Silselah outfall indicate its main external anthropogenic origin. However, the positive correlations of DON with salinity, pH and ammonium in the bottom water possibly reflect the DON source from living organisms. The highest particulate nitrogen (PN) averages were in the vicinity of Kayet Bay discharges. The regression equation between PN and suspended particles confirms external input of PN.