Change detection using remote sensing in a reef environment of the UAE during the extreme event of El Niño 2015–2016

Coral reefs of the United Arab Emirates (UAE) are living in the
world’s hottest sea. Recently, corals harbouring Symbiodinium
thermophilum, a thermotolerant microalgae, were found to be
prevalent among UAE reefs and were reported to endure extreme
sea-surface temperatures. Late 2015–early 2016 was marked with
the strongest El Niño on record worldwide, which caused massive
coral bleaching (loss of symbiotic microalgae from reef-building
corals). In September 2015, the waters flanking UAE coasts were
identified to be among the areas facing a thermal stress reaching
its highest level liable to cause massive coral bleaching. However,
the effect of this thermal stress on UAE corals remained largely
unknown. Here, multi-temporal DubaiSat-2 satellite images were
used to show that changes in the reef environment of Dalma
Island, UAE, between 2014 and 2016, occurred in macroalgaedominant
habitats, whereas live corals remained unaltered.
Furthermore, extending the study to a larger area helped in discovering
a continuum of live and pristine corals, which was not
reported or studied before. While sea-surface temperature anomalies
of 1°C were reported to significantly damage coral reefs
around the world, the live coral habitat was observed to exhibit
no-change despite four consecutive months of +2°C to 3°C
anomalies reported during the study period. These findings
point to the tolerance of UAE live corals faced with extreme
climate conditions