The reefs of the Gulf of Mannar have been reasonably well-studied thanks to their proximity to Institutions like Central Marine Fisheries Research Institute, Central Salt and Marine Chemicals Research Institute, Madurai Kamaraj University and Center of Advanced Studies in Marine Biology. So far, a total of 91 species of corals under 35 genera have been recorded from these reefs. Other groups that have been studied extensively are marine algae, echinoderms, mollusks, sponges and polychaetes.

Very few of the 20 reefs are in reasonably good shape. The northern islands, especially Kurusadai and Shingle have been heavily impacted due to collections by college and university students over several decades. The southern ones near Tuticorin have been affected by industrial pollutants, especially fly ash and liquid effluents from onshore industries. Most other reefs have been extensively mined for coral blocks and debris. With the inclusion of all these reefs in the Gulf of Mannar Biosphere Reserve, mining has been almost stopped though clandestine removal is still a possibility.

The Gulf of Mannar reef formations are of fringing type, developed around 20 islands located in a chain between Tuticorin (8º48`N; 78º9`E) and Rameswaram (9º14`N; 79º14`E), on the SE coast of India. The reef around the Rameswaram Island extends into the Palk Bay as an 8 km long fringing reef along the mainland coast.