MESOPHOTIC CORAL ECOSYSTEMS – A LIFEBOAT FOR CORAL REEFS?
30
The towns of Aqaba and Eilat, located on the northernmost
coast of the Gulf, are both large population centers with
significant infrastructure development. The 14 km long
shallow reef in Eilat was once a flourishing natural ecosystem,
but in the last 40 years has been increasingly impacted by
human activities (Loya 1975, 1976a, 2004, 2007, Walker and
Ormond 2003). Extensive parts of the reef have been destroyed
as a result of multiple factors, including inexperienced divers
(Walker and Ormond 2003), sewage spillages, oil spills
(Loya and Rinkevich 1980) and natural disturbances, such
as extreme low tides (Loya 1972, 1976a) and severe southern
storms (Eyal et al. 2011, NMP 2013). The shallow-water corals
do not generally experience bleaching — although it has
been hypothesized that they have been genetically selected
to tolerate periods of elevated water temperature (Fine et al.
2013), new coral diseases have been reported (Rosenberg and
Table 1.
Data summary for scleractinian coral cover (per cent) at Eilat IUI reef, mean Shannon-Wiener index of diversity (H’), mean number
of species per quadrat (#), and total number of species of all corals observed along the survey transects at 2 m, 40 m and 60 m. The survey
includes three transects of 10 quadrats at each depth, with a total of 30 m
2
per depth (Eyal 2012).
Ben-Haim 2002). In contrast, some of the mesophotic corals
have been observed to suffer from partial bleaching during
the summer, followed by recovery in the autumn (Nir et al.
2014). Bleaching is most pronounced on the lower edge of
the reef slope between 40 and 63 m. It has been suggested
that temperature alone is not responsible for the bleaching.
Instead it may be due to a complex seasonal acclimatization
regime that results in an oscillation in the mesophotic coral-
algae relationship frommutualistic in the summer to parasitic
in the winter (Nir et al. 2014).
Currently, Eilat’s reefs are continuouslymonitored by the Israel
National Monitoring Program at the Gulf of Eilat. Gradual
improvement in reef healthhas been recorded in some shallow-
water locations, but there is still little information on MCEs
(NMP 2013).
2
40
60
23.95
34.23
33.04
1.00
2.33
1.83
3.714
8.375
6.121
1.329
2.918
1.728
10
25
20
Depth
(m)
Mean per
quadrat (#)
Mean per
quadrat (SD)
Total no.
of species
Diversity
( H´)
Cover
(%)
Data summary for scleractinian corals at Eilat reef