Coral reefs recovery post bleaching event in Central Tapanuli, North Sumatra

Abstract

Abstract Temperatures on the west coast of Sumatra, South Java, Bali, and Nusa Tenggara in the Indian Ocean rose dramatically in 2016. The extreme increase in temperature greatly affects sea surface temperature and coral reef ecosystems. Central Tapanuli waters were also the area that could not escape this phenomenon. Coral bleaching has caused damage to coral reefs which is characterized by decreasing live coral’s cover. Observations on coral reef recovery have been carried out at 13 sites in Central Tapanuli waters. Observations were made using the UPT (Underwater Photo Transect) method to determine live coral’s cover. The coral fish density was determined using the UVC (Underwater Visual Census) method. From the observations, coral cover decreased by 57,68% in 2016. Observations were made in 2015, 2016, 2018, and 2021. Observations in 2018 have shown increasing live coral cover by approximately 5%. Meanwhile, in 2021 there was an increase in live coral cover by approximately 8.25% from 2018. Even though coral composition changes and mostly the number of coral decreases, after 5 years, the number of corals starts to increase. The reef health index likewise rises in tandem with these changes. Despite some chronic stress being present at some places, the water quality was favorable for coral recovery.