Microbial enzymatic activities of α- Amylase and β- Galactosidase enzymes were measured  seasonally in marine water samples that were collected from two sites located at the south Levantine Sea basin of the Mediterranean Sea of Egypt, Port Fouad city in the east and Alexandria city in the west during four successive seasons from autumn 2014 to summer 2015. Determination of microbial enzymatic activities were carried out by determining reducing sugars using DNS reagent. This research provided a newly applied method for the determination of microbial enzymatic activities in natural open water system, the Mediterranean Sea. The applied methodology involved using marine water samples as the source of crude enzyme , eliminating the difficulties of extracting an enzyme from specific microorganism as well as avoiding the adjustment of aseptically required conditions for the inoculation and incubation of the desired microorganism in culture media tube under the laboratory conditions while providing almost natural conditions for the microbial community represented in water samples. The water samples were chemically analyzed to determine the effect of certain metal ions concentrations on the enzymatic activities of the microbial α- Amylase and β- Galactosidase enzymes. The results showed that though water samples were collected from the same marine source yet, spatial variations occurred between the two sampling sites and seasonal variations at the same sampling sites which were attributed to the naturally occurring environmental variations during the different seasons of the year.

Keywords : α-Amylase, β-Galactosidase, Bacteria.