Many species of crustaceans, mollusks, gastropods and fishes have been observed to inhabit the seagrass beds. The Gulf of Mannar harbours a total of 117 species of coral belonging to 7 genera. Coral reefs serve as the spawning grounds for fisheries, seagrass beds as nursery grounds and mangroves as shelters form a unique component of life-support systems of coastal biodiversity that relates to global benefits and local needs. Seventeen different mangrove species occur within the Biosphere reserve area. The coastal mangrove Pemphis acidula, is endemic to Gulf of Mannar.
Coastal mangroves are important nursery habitats and biodiversity reservoirs in coastal areas.
The Gulf's seagrass communities are valuable habitats for commercially harvested species, particularly the green tiger prawn Penaeus semisulcatus, which is extensively harvested for the export market. Halothurian, an endemic echinoderm found in abundance in Gulf of Mannar, is extensively exploited for export to Japan and other Southeast Asian countless as a highly priced food item for human consumption. The economically viable species of seaweeds such as Hypnea, Gelidiella, Gracelaria, Stiechospermum, Hydroclathums, Clathatus, Padina, Caulerpa are largely distributed in the Gulf of Mannar. In addition, ornamental shells, chanks, and pearl oysters are exploited in the Gulf. Sea fans and seaweeds are exported for industrial and decorative purposes.