We e amined the surface nutrient regime and hypo ia in Manila Bay, Philippines, during the southwest monsoon along a transect from off Limay, Bataan Peninsula, to Metro Ma nila. The water column showed stratification, with warm, less saline water in the top 10 meters overlying cold, saline bottom water. Hypo ia was present in the bottom waters along the entire transect, and ano ic conditions were observed off Manila. Ammonium concentrations ranged from 6.7 to 40.2 µM, e ceeding those of nitrate and nitrite, both of which were nearly depleted at almost all stations e cept off-Manila, with levels below 0.1 µM. Phosphate varied from 0.1 to 1.9 µM, resulting in a stoichiometrically nitrogen-rich condition at the surface, with N:P ratios ranging from 17.1 to 149.7 and an average of 37.4. This is in contrast to the phosphate-rich con ditions reported during the northeast monsoon period. A plume with high nutrient concentrations and high chlorophyll a was observed off Manila, indicating freshwater inflow from sewage and the Pasig River. Diatoms, including the Skeletonema costatum comple and Chaetoceros spp., were abundant, and these eutrophic conditions likely favored the occurrence of green Noctiluca, while it was not observed during our study.departmental bulletin pape
