We studied if functional traits related to resource preemption (light and inorganic nutrients) exert control on space preemption of tropical seagrass meadows. Additionally, we studied if space preemption changed under different eutrophication scenarios. We took seagrass abundance data to study space preemption, seagrass traits data to study their effect on space preemption and eutrophication indicators to evaluate the level of eutrophication at each site/sampling event. The data was collected in Unguja Island (Zanzibar Archipealgo, Tanzania) in seven sites/sampling events (Harbor, Chapwani, Changuu, Bweleo, Fumba, Mangroves and Marumbi). Each site/sampling event comprised a subtidal seagrass meadow (2-4 meters depth) of around 2500 square meters, delimited by the coastline and a fringing reef. The data was taken between the 26.09.2016 to the 05.10.2016. In each site/sampling event, five 50 meters transects were deployed perpendicular to the coast and paralel to each other, approximately separated by 50 meters. The areas enclosed beweeen the transects were names A, B, C and D. δ15N was collected as an indicator of eutrophication. We took one 50ml surface sediment sample per transect for delta 15 nitrogen analysis. The samples were stored at −20°C and transported frozen to the Leibniz Centre or Tropical Marine Research. They were then dried at 50°C in a forced air oven until constant DW, ground to a fine powder with mortar and pestle, and weighed into tin capsules prior to analysis for nitrogen stable isotope composition (δ15N ) with a gas isotope ratio mass spectrometer (Thermo Finnigan Delta Plus). Results are expressed in delta notation (‰) where the standard for delta 15 nitrogen is atmospheric nitrogen.