Data from: Deep oxygen-depleted Red Sea coral reef depressions sustain resistant ecosystems

Persistent oxygen-depleted zones in the ocean are known primarily from
enclosed basins in temperate regions or the open-ocean (including oxygen
minimum and limiting zones). However, little is known about the potential
for such zones in tropical coastal domains, despite warmer temperatures
and complex geomorphological structures in some tropical areas increasing
the likelihood of their existence. Here, we report two subsurface
oxygen-depleted zones within deep depressions of the Red Sea’s Difaht
Farasan—a carbonate platform hosting the world’s third-largest contiguous
tropical coral reef system. One zone maintains suboxic oxygen levels
(~11-14 µmol kg⁻¹), while the other sustains oxygen levels below detection
(<2 µmol kg⁻¹). The suboxic zone shows no fixed nitrogen loss,
while the near-anoxic zone hosts anaerobic microbial populations and shows
signs of nitrogen loss. We propose that the warm and saline environment of
the Red Sea interacts with the semi-enclosed depressions to restrict
vertical mixing, limiting oxygen resupply at depth. However, unlike most
other oxygen-depleted zones, our deep-sea vehicle surveys demonstrate that
these zones support resistant aerobically respiring taxa, indicating an
unusual capacity to reduce aerobic oxygen demands at high temperatures
(>21°C). Targeted exploration of deep tropical coastal environments
is crucial for determining if similar zones exist beyond the Red Sea and
understanding their potential responses to climate change.