Study of Nutrient Salts, Chlorophyll-a and Physicochemical Condition in El-Mex Bay Water, Alexandria, Egypt

Abstract

The present work aimed to study the physicochemical parameters and nutrient salts of El Mex Bay area to evaluate its composition since El- Mex Bay exposed to several kinds of human activities and receive different types of industrial pollutants. Various pollutants are dumped daily by industrial, agricultural and domestic sources over Alexandria coasts through several outfalls, El-Mex Bay one of these disposal sites (El-Mex Pumping Station). Surface and bottom water samples were collected seasonally during the period from September (summer) 2012 to April (spring) 2013. Salinity variation appeared in water quality changes, it ranged from 2.25‰ to 38.87‰ and from 26.21‰ to 39.64‰ at the surface and bottom water, respectively. Dissolved oxygen levels indicated poor aeration conditions along the water column, it is lower in most stations at surface layer (ND-3.15 mgl -1 ) than that in the bottom layer (0.79 – 6.28 mgl -1 ). The pH values of the study area at surface ranged (7.05 - 8.73), while at the bottom water ranged (7.18 - 8.45). Inorganic nitrogen species in El-Mex Bay water decreased in the order of NH4 + > NO 3 - > NO2 - . The measured nutrient content varied greatly as follows: NH4 + , 4.73±5.70 to 99.27±72.53 µM; NO 2 - , 0.72±0.43 to 4.34±3.43 µM; NO3 - , 1.33±1.01 to 31.68±24.59 µM Regional and seasonal variations of total nitrogen concentration in El-Mex Bay surface and bottom water ranged from 28.26± 14.87 to 335.12±226.66 µM. The concentrations of reactive phosphate (PO 4 ) and total phosphorus (TP) were in the ranges of 0.05-17.36 µM and 0.11-28.01 µM, respectively. As a result of nutrient enrichment, phytoplankton growth was very intensive, reflected by an abnormally high concentration of chlorophyll-a (annual average: 13.64±10.69 μ g l −1 at surface and 3.96 ±2.42 μg l -1 at bottom water).