Mesophotic Coral Ecosystems

MESOPHOTIC CORAL ECOSYSTEMS – A LIFEBOAT FOR CORAL REEFS?

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

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).

23.95

34.23

33.04

1.00

2.33

1.83

3.714

8.375

6.121

1.329

2.918

1.728

Depth

(m)

Mean per

quadrat (#)

Mean per

quadrat (SD)

Total no.

of species

Diversity

( H´)

Cover

(%)

Data summary for scleractinian corals at Eilat reef