Contents: 1. Introduction. 2. Distribution of seagrasses. 3. Seagrass associated fauna. 4. Importance of seagrass ecosystem. 5. Threats to seagrass ecosystem. 6. Mitigation. 7. References. From the introduction: Marine ecosystem of the planet earth represents 70.8% or 362 million km2 with a total 1.6 million km of coastline. A total of 123 countries of the globe represents the coastal as well as marine ecosystems. Coastal ecosystem extends from the coastline to depths less than 50 m while rest of the areas fall under marine ecosystem. Coastal zone and continental regions are the combination of several ecosystems like mangroves ecosystem, estuarine ecosystem, backwaters, rocky coastal areas, salt marshes, lagoons, sandy beaches, seagrasses ecosystem and luxuriant coral reefs ecosystem. India harbors 7516.6 km of coastline with exclusive economic zone (EEZ) of 2.02 million km2 including 0.86 million km2 on the western coastal areas, 0.56 million km2 on the eastern coastal areas while Andaman and Nicobar Islands share 0.6 million km2 (Venkataraman and Raghunathan, 2015). Seagrasses are considered as under group of flowering plants. They grow and develop in fully submerged and rooted condition in estuarine as well as marine environment. Seagrasses if the world belong to the class monocotyledons with total 60 species from four families viz., zosteraceae, Posidoniaceae, Hydrocharitaceae and cymodoceaceae. These monocotyledons are with multiple evolutionary origins and are polyphyletic in nature. They have emerged several types of adaptation to enable survival in niche (Green and Short, 2003).