Diatoms constitute an important component of the fouling community. Although a lot of work has dealt with the fouling diatom community structure, work on the species interactions within the community is still meager. In this regard, a study was carried out by transferring the natural diatom biofilms into controlled conditions so as to understand the roles of nutrients, initial cell inoculum and the seasonal variations in species composition in structuring the fouling diatom community. The diatom community exhibited seasonal variations during the monsoon, postmonsoon and premonsoon periods. During each of these seasons, the diatom species interactions varied depending upon the species composition. It was observed that excess nutrients favored those species with comparatively higher growth rates thereby suppressing the growth of other co-existing species. This competitive trait was found to be effective at an appropriate cell density ratio of the competitive and target species. Understanding such pathways will be useful for modeling the fouling diatom species interactions in various habitats under different resource conditions.