Algae are highly adaptable and can thrive in different environments, making them ideal for synthesizing effective and affordable antibacterial compounds. To optimize the harvesting of marine algae and determine the period during which the algae display maximum activity, we studied the effect of seasonal variation (during a closed year) and temperature and salinity on the antimicrobial activity of fifteen species of algae (four species belonging to the Chlorophyceae class, two species belonging to the Phaeophyceae class and four species belonging to the Rhodophyceae class). These algae were tested for their antimicrobial activity against S. aureus, B. cereus, E. coli, and C. neoformens. These observations reveal that the optimal harvesting season for phaeophyceae and rhodophyceae extracts is spring, whereas that for chlorophyceae is during the summer period, when temperature and salinity are at their highest. In this study, it was found that the largest inhibition diameter of algae extracts occurs during summer.