Assessing the invasion and impact of coral-killing sponge Terpios hoshinota on coral reefs in the Gulf of Mannar marine biosphere reserve: A case study and review

Abstract

The encrusting cyanobacteriosponge Terpios hoshinota Rützler & Muzik, 1993 has caused severe and often irreversible damage to coral reefs and associated benthic communities in the Indo-Pacific region. Despite its ecological significance, the distribution patterns of T. hoshinota in Indian reefs is poorly understood except for limited reports. Hence, a comprehensive investigation was conducted between September 2018 and August 2019 to assess the range extent of T. hoshinota across 21 islands within the Gulf of Mannar Marine Biosphere Reserve (GoMMBR), located along the southeast coast of Tamil Nadu, India. Utilising coral video transect methodology, a notable outbreak of T. hoshinota primarily on Montipora digitata reefs in Thalaiyari and Valai Islands was documented, where approximately 42.8 % and 45 % of M. digitata coral cover were killed. Furthermore, mild to moderate infestations of T. hoshinota were observed on Porites corals in seven additional islands within the GoMMBR. There were no other factors except T. hoshinota that caused the corals to die (no polyps on the corals). The rapid spread of T. hoshinota from infested corals to other healthy corals was evidently accelerated by coral-coral interactions.