Effects of Surface Microlayer and Sediment Water Interface Layer on the Nutrient Species in the Eastern Harbour of Alexandria

The Eastern Harbor (EH), a small shallow semicircular basin surrounded by Alexandria, has an area of 2.53 million m², with an average depth of 6.5 m and water volume of 16.44 million m³. It is sheltered from the Mediterranean Sea by a water break leaving two openings through which the harbor water is connected to the open seawater. The EH is mainly influenced by sewage disposal from Alexandria. Water samples were collected seasonally at three selected stations from the surface microlayer (SML) to sediment water interface layer (SWIL) for studying the effects of SML and SWIL on the distribution of nutrient species in the rest of the water column; middle water layer (MWL). Contrary to nitrate and particulate nitrogen, the annual means of the rest of parameters (nitrite, ammonium, dissolved organic nitrogen, dissolved inorganic, organic and particulate phosphorus and silicate) in the SML were higher than the corresponding means in the SWIL, confirming that contribution of these nutrient species from the SML to the MWL was more than that from the SWIL to the MWL, which generally gave intermediate annual means. Accordingly, it could be concluded that most of the nutrient species in the EH originated mainly from an allochthonous source (untreated domestic wastes) floating over the surface harbor water rather than from the autochthonous sources; decomposition of organic remains and release from the harbor sediments.