Monitoring of coral-killing sponge (Terpios hoshinota) caused rapid coral tissue loss assessment through environmental parameters in the Palk Bay

Abstract

Coral-killing cyanobacteria sponge T. hoshinota has been affecting the Palk Bay coral reef since 2009, causing rapid destruction to coral tissues. Monitoring studies provide essential information on the prevalence of T. hoshinota and an understanding of the environmental parameters contributing to coral tissue loss, further helping conservation policies to be made. The study conducted a benthic transect survey using the standard method in 2017 and 2020 in the Palk Bay region. Results revealed that T. hoshinota prevalence has increased by 46.68% from the 2017 survey; it was (Mean ±SE) 11.25 ± 1.01% in 2017 and 21.09 ± 1.53% in 2020. Coral mortality due to T. hoshinota impact was observed in the 2017 survey at 0.84 ± 0.06% and significantly increased (75.29%) in the 2020 survey, recorded at 3.42 ± 0.11%. The Pearson correlation plot showed that SST and PAR were strongly correlated during the survey periods, while turbidity has not been correlated with any other environmental parameter. The R-based hierarchical regression analysis revealed that environmental parameters NO3 (β=0.58; p = 0.004) and PAR (β=0.35; p = 0.02) were associated with T. hoshinota causing rapid tissue loss in the Palk Bay coral reef. The coral-killing sponge T. hoshinota and associated environmental parameters rapidly progressed over the study period in the Palk Bay coral reef, resulting in rapid tissue loss and coral mortality. Consequentially, the live coral cover in Palk Bay would decline. Hence, T. hoshinota based conservation management activities have to be made in Palk Bay.