Abstract
Coral reefs are experiencing a dramatic loss of hard coral abundance and associated habitat structure from a myriad of local and global factors. Here, utilizing U–Th radiometric age-dating of coral death assemblages, we investigated patterns of coral mortality from the eastern margin of the Red Sea along a latitudinal gradient (Yanbu, 24
o
N; Thuwal, 22
o
N; Al-Lith, 19
o
N; Farasan Banks, 18
o
N) in 2018 and 2019. In all four regions, radiometric ages of in situ dead
Acropora
and
Pocillopora
colonies were largely confined to the late twentieth and early twenty-first century. During the early twenty-first century, coral mortality was found to be synchronous with previously documented bleaching events in 2010 and 2015 and, at one site (Farasan Banks), an outbreak of crown-of-thorns starfish (COTS) in 2009. The most northern site, Yanbu, had the highest relative percentage of live coral (42 ± 4%) and of living
Acropora
, and may serve as a refugium under climate warming scenarios
.
For the three southern regions (Thuwal, Al-Lith, Farasan Banks) benthic structure was mostly comprised of dead corals. The southernmost survey site, Farasan Banks, underwent a dramatic change in coral benthic structure associated with a COTS outbreak in 2009 and a bleaching event in 2015, and had the lowest relative percentage of live coral (6 ± 2%), comprised mostly of massive
Porites,
with no live
Acropora
or
Pocillopora
. Our results highlight the asynchronous impact of disturbance events on eastern Red Sea coral reefs and emphasize regional differences in recovery and ecosystem state.