[Coral-List] Refugia against bleaching in the Red Sea

Eslam Osman eom.osman at gmail.com
Thu Nov 2 11:58:51 EDT 2017

Hi all,

I would like to mention a successful story of bleaching at the northern Red
Sea. The place that is considered a safe-haven for corals against climate
change, and actions must be taken to protect the region to keep it as a
genetic reservoir. Please read more about that in our recent published
paper in Global Change Biology.


Here is the abstract:

Tropical reefs have been impacted by thermal anomalies caused by global
warming that induced coral bleaching and mortality events globally.
However, there have only been very few recordings of bleaching within the
Red Sea despite covering a latitudinal range of 15° and consequently it has
been considered a region that is less sensitive to thermal anomalies. We
therefore examined historical patterns of sea surface temperature (SST) and
associated anomalies (1982–2012) and compared warming trends with a unique
compilation of corresponding coral bleaching records from throughout the
region. These data indicated that the northern Red Sea has not experienced
mass bleaching despite intensive Degree Heating Weeks (DHW) of >15°C-weeks.
Severe bleaching was restricted to the central and southern Red Sea where
DHWs have been more frequent, but far less intense (DHWs <4°C-weeks). A
similar pattern was observed during the 2015–2016 El Niño event during
which time corals in the northern Red Sea did not bleach despite high
thermal stress (i.e. DHWs >8°C-weeks), and bleaching was restricted to the
central and southern Red Sea despite the lower thermal stress
(DHWs < 8°C-weeks). Heat stress assays carried out in the northern
(Hurghada) and central (Thuwal) Red Sea on four key reef-building species
confirmed different regional thermal susceptibility, and that central Red
Sea corals are more sensitive to thermal anomalies as compared to those
from the north. Together, our data demonstrate that corals in the northern
Red Sea have a much higher heat tolerance than their prevailing temperature
regime would suggest. In contrast, corals from the central Red Sea are
close to their thermal limits, which closely match the maximum annual water
temperatures. The northern Red Sea harbours reef-building corals that live
well below their bleaching thresholds and thus we propose that the region
represents a thermal refuge of global importance.


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