Mass coral bleaching and mortality associated with high sea surface temperatures in the summer of 2022 in Sekisei Lagoon, Okinawa, Japan

Abstract

The largest coral reef region in Japan, Sekisei Lagoon, experienced widespread coral bleaching and mortality in the summer of 2022 as a result of anomalously high sea surface temperatures. Bleaching impacts were recorded at 30 sites within Sekisei Lagoon. With Degree Heating Weeks (DHWs) exceeding 13.20°C-weeks, resulted in 63% of corals experiencing bleaching and 14% of the corals facing bleaching-induced mortality. Similar to the 2016 bleaching episode, Acropora species were the most affected coral genera in terms of abundance in Sekisei Lagoon, with 54.8% of the population experiencing severe bleaching and 20.7% of colonies experiencing colony mortality. Our analysis suggests that repeated heat events may have enhanced bleaching resistance at some sites in Sekisei Lagoon, as the total coral cover remained stable one year after bleaching.