Research on the profile of Fe in the seagrass ecosystem has been carried out. Analysis of seawater, sediment, seagrass samples from the association of mangroves, mangroves-coral reefs and coral reefs taken in the waters of Donggala Regency was carried out using the ICP-OES method (Inductively Coupled Plasma-Opticaly Emission Spectrometry). It turns out that seagrasses associated with mangroves have higher iron concentration in their ecosystem, both in waters, sediments, and in seagrass plants and will be lower in association with mangroves and their association with coral reefs. Likewise, the status of seagrass has a higher concentration of Fe than infertile status or poor status. The results become some reference to show that seagrass plants can be bio-indicators of marine waters fertility.