Phytoplankton bloom in the Gulf of Elat/Aqaba was studied before mainly using one-dimensional models and observations from the northern Gulf. Thus, the spatial variability within the Gulf and the contribution of physical processes such as horizontal advection to the bloom have not yet been studied. Moreover, various factors such as light limitation are still debated. Here we used a three-dimensional coupled physical-ecological model for the Gulf of Elat/Aqaba to study the mechanisms for phytoplankton bloom throughout the Gulf. We found the southern surface bloom to be higher than the northern surface. In contrast, southern integrated bloom is lower than the northern bloom. These differences are due to spatial variations in the mixed layer depth, which
is much deeper in the northern Gulf compared with the south. Moreover, horizontal advection controls phytoplankton integrated biomass during the bloom, a process often neglected when dealing with phytoplankton
blooms. Finally, we found that light limits growth of the northern integrated bloom.