Abstract: Total viable heterotrophic aerobic marine bacteria attached to the leaves of Avicennia marina L. from two sites of a mangrove forest along the Qatari Coast did not show significant differences between sites. Maximum counts were recorded in both sites during September and October 1998 and lowest during May and April for site 1 and 2 respectively. Of the 5 bacterial groups studied, proteolytic bacterial counts in both sites were slightly higher then cellulolytic, amylolyic and lipolytic bacteria. Cellulolytic counts were rather prominent in site 2 during July 1998 to February 1999. However, spore formers were very low in both sites. The attached bacterial abundance and densities are correlated with counts in sea water of the mangrove sites. These bacterial variations may be related to atmospheric and leaf temperatures and probable inhibiting substances released by the plant leaves. The concept that only small part of the microbial community is active at any given time appears to be inviting in such cases.