Twenty-one species of sponges were recorded under the class of Demospongiae and Calcareous sponges of which 19 species were new to Agatti reef. A total of 113 Sponge endosymbiotic bacterial strains were isolated from twenty-one species of sponges and screened for antimicrobial activity. Five bacterial strains of sponge endosymbiotic bacteria (SEB) namely SEB32, SEB33, SEB36, SEB43 and SEB51 showed antimicrobial activity against virulent marine fish pathogens such as Vibrio alginolyticus, Vibrio vulnificus, Vibrio parahaemolyticus, Aeromonas salmonicida, Flavobacterium sp., Edwardsiella sp., Proteus mirabilis and Citrobacter brackii. The secondary metabolites produced by SEB32 from sponge Dysidea fragilis (Montagu, 1818) [48] was selected with broad range of antibacterial activity and subjected for production, characterization by series of chromatography techniques and spectroscopic methods. Based on the results of FT-IR and mass spectrometry, the active molecule was tentatively predicted as "Pyrrol" and the structure is Pyrrolo[1,2-a]pyrazine-1,4-dione, hexahydro- with molecular formula of C7H10N2O2. The LC50 of active molecule was 31 μg/ml and molecular weight of the metabolites was 154. The potential strain SEB32 was identified by gene sequence (GenBank Accession number JX985748) and identified as Bacillus sp. from GenBank database.

Photographic evidence of some important coral diseases (black band disease, black disease/Terpios hoshinota, white syndrome, pink line syndrome, pink spots, invertebrate galls, skeletal growth anomalies, tissue loss), coral competing sponges, and coral–algal phase shifts (competitive overgrowth of the seaweed Caulerpa spp. over corals and competitive scleractinian interactions such as with Halimeda spp.) have been collected during field observations in a few atolls within the Lakshadweep archipelago, Arabian Sea. Further, earlier reports of similar diseases and other stressors within the Indian Exclusive Economic Zone (EEZ) and its contiguous international waters, including the reefs of the Maldives and Sri Lanka, are highlighted and their distributional ranges are shown.

Our study documents the outbreak of a coral-killing sponge Terpios hoshinota in the coral reefs of Lakshadweep archipelago and highlights that it has further extended its territory into the isolated atolls of Arabian Sea and maybe a growing threat to the existing coral reefs in the region.

Our study documents the outbreak of killer sponge Terpios hoshinota on the coral reefs of Lakshadweep archipelago and highlights that the killer sponge has further extended its territory in the isolated atolls of the Indian subcontinent.