A comparative field study was performed to assess the heavy metals contamination in surficial sediments of highly and less polluted zones at the northern part of the Suez Gulf. In addition, to highlight the relationship among metal contamination and enzyme activity. Seven heavy metals Mn, Fe, Pb, Cd, Zn, Ni, and Cu were analyzed using atomic absorption spectrophotometer. The activity of enzymes (alkaline phosphatase and urease) was estimated in the sediment samples. The statistical results showed that there were high significant differences at p ≤ 0.01 among Cu, Pb, Cd, Ni, Mn and Zn between highly polluted and less polluted sediments. Urease activity had no significant relationship with the tested metals concentrations. Cd, Cu, Mn, Ni, Pb and Zn may inhibit alkaline phosphatase activity. Alkaline phosphatase activity showed high significant difference at p ≤ 0.01 between summer and winter seasons in highly polluted sediment. Moreover, there was significant seasonal difference in Pb concentration at p ≤ 0.01 in the same category. Correlations of the enzymes with each metal showed that alkaline phosphatase activity had significant negative correlation coefficients (r = −0.55, −0.49, −0.27, −0.37, −0.37, and −0.60) with Cu, Cd, Fe, Ni, Zn and Pb respectively in winter, but only with Zn (r = −0.46) in summer season. As a result, ALP activity can possibly be used as a predictor and sensitive indicator of heavy metals bioavailability in marine sediments.
