Bleaching Impacts on the Last Remaining Acropora-dominated Reefs in the United Arab Emirates

Coral reefs in Arabian Gulf and Gulf of Oman waters of the United Arab Emirates (UAE) have historically been dominated by Acropora corals. By early 2021, however, extensive Acropora cover remained at only two UAE locations: the fringing reefs of Sir Bu Nair Island (SBN) (Arabian Gulf) and Khor Fakkan (KF) (Gulf of Oman). A summer 2021 marine heatwave impacted these last Acropora refugia and caused the first mass bleaching event on the UAE’s Gulf of Oman coast. Benthic surveys were conducted before, during and eight months after this event. Bleaching severity was high, with 41% of hard corals bleached in KF and 93% in SBN. Total live coral cover declined from 68% to 25% at KF and from 36% to 9% in SBN during bleaching. Acropora cover declined from 23% to 2% in KF and from 19% to 0.02% in SBN during bleaching. There was limited recovery eight months after bleaching. Community composition shifted away from Acropora toward heat-tolerant taxa, particularly Porites and Dipsastraea, with increased homogenization of coral assemblages. These last Acropora refugia could have served as valuable sources of larvae to support coral recovery elsewhere in UAE waters, highlighting the importance of conservation and restoration efforts.