Fig. 5: Source of the brine.

Microbial staining suggests the main pool is fed by brine released from the toe-of-slope of the eastern margin of the Gulf of Aqaba. This microbial community occupies a niche defined by the presence of hypersaline brine interfacing with oxygenated normal marine waters. Hence, the microbial stain is restricted to the shore of the brine pools and cases where brine emanates from the seabed. a Shows a breccia block partially buried in hemipelagic sediment at the toe-of-slope. Microbial stain suggests that this block has mobilized brine from the sediment which flows via gravity into the pool below. b Captures brine weeping from the toe-of-slope into the main pool. c Shows another breccia block beneath which brine is liberated into the pool. Notice abundant shrimps Plesionika sp. (Pandalidae) which were observed scavenging animals stunned or killed by the anoxic brine. In d, e, up to 5 m above the pool, brine seeps from the slope. f Outcrops from the toe-of-slope 1 m above the pool. The stratigraphy is interleaved with a conspicuous sheeted horizon (arrowed) determined via XRD to be composed of aragonite, high- and low-Mg calcite with a minor contribution of orthoclase feldspar, indicative of enhanced diagenesis of foreslope sediments in the presence of hypersaline waters.