Unexpected ecosystem found deep below Red Sea Coral Reef

Scientists from King Abdullah University of Science and Technology (KAUST) and the National Center for Wildlife (NCW) report in PNAS NEXUS an unusual ecosystem below the third largest coral reef system in the world and biggest in the Red Sea. Found in Difat Farasan, otherwise known as the Farasan Bank and located near the border between Saudi Arabia and Yemen, deep waters were inhabited by corals, fish and other animals not expected to survive in conditions of such low oxygen and high acidity.  

Several of the creatures showed unexpected coping strategies to the extreme environment. Fish swam slower, and corals were healthy in conditions that normally prevent the calcification of their skeletons. Calcification is necessary for coral growth and survival. 

"The ability for these animals to live in warm, oxygen-depleted zones suggests they have an unusual ability to reduce how much oxygen they use to sustain life. This discovery highlights the need for greater marine exploration of deeper layers tropical coastal areas, as they may hold unexpected ecosystems.” said KAUST Research Scientist Dr. Shannon Klein, who led the study. 

Although underwater, fish, corals and many other sea creatures need oxygen to survive. While their bodies have evolved differently from land animals to metabolize oxygen, they too asphyxiate if oxygen levels drop dangerously low. However, in the Red Sea, there are resistant ecosystems. Considering that oxygen depletion in the sea is one consequence of rising temperatures, greater study of how these creatures exist there may help us understand how marine life can withstand the challenges of climate change.  

Coral reefs usually exist in shallow waters. But the study found depressions that went more than 200 m deep throughout the Farasan Bank coral reef system.  

"This research highlights the significance of the Red Sea as a natural laboratory for studying marine resilience. Discovering ecosystems that thrive in extreme conditions expands our understanding of how marine life adapts and reinforces the need for continued exploration and conservation of these unique habitats," said Dr. Mohammad Qurban, CEO of the National Center for Wildlife and contributor to the study. 

KAUST Assistant Professor Froukje van der Zwan, Associate Professor Francesca Benzoni and KAUST Ibn Sina Distinguished Professor Carlos Duarte also contributed to the study.