A decade of benthic changes on coral reefs in the Southern Persian/Arabian Gulf (2010–2020)

In recent decades, extensive coral mortality throughout the Persian/Arabian Gulf (PAG) from thermal stress events has led to increasing reef degradation and the loss of biodiversity across the region. To quantify these dynamics, water temperatures and benthic cover were monitored on ten reefs spanning about 350 km in the Southeastern PAG (Abu Dhabi) over a 10-year period. Water temperatures measured on the reefs fell into cooler (2010–2015) and warmer (2015–2020) periods. 2010–2015 had lower mean winter minimum (19 °C vs. 19.56 °C) and lower mean summer maximum (35.3 °C vs. 35.8 °C, coral bleaching threshold is 35.7 °C). Over the decade, mass coral bleaching occurred in seven years with four bleaching years after 2015. Coral cover decreased by 78% while turf and coralline algae strongly increased (66% and 154%, respectively), and fleshy macroalgae also collapsed in cover (− 83%). Cyanobacteria increased by 980% from 2017–20 with concurrent coral bleaching but without becoming spatially dominant. Despite the decline in coral cover, no shift into a macroalgae-dominated system occurred.