Direct Measurement of CO₂ Air-Sea Exchange Over a Desert Fringing Coral Reef, Gulf of Eilat (Aqaba), Israel

Understanding the role of coral reefs on air-sea CO₂ exchange is essential to accurately estimate carbon budgets throughout the tropical and subtropical oceans. Results from research conducted in humid marine environments show coral reefs are mainly net sources of CO₂ to the atmosphere due to calcification being dominant over respiration and dissolution. However, coral reefs are also found bordering deserts in the subtropical high-pressure belt. Here, we present results from concurrent direct measurements of air-sea CO₂ exchange over fringing coral reefs and open sea bordered by hyper-arid deserts in the Gulf of Eilat (Aqaba). The fringing coral reefs were found to be a net sink of CO₂ at −1.62 ± 4 μmol m⁻² s⁻¹ sequestering 1.96 times more CO₂ than adjacent open sea. The CO₂ fluxes showed a negative correlation with some local meteorological parameters such as humidity, wind speed, and net radiation but were positively correlated to air temperature. The air-sea CO₂ fluxes were also found to be correlated with dust, which is believed to trigger metabolic processes in bacteria and phytoplankton in the low-nutrient, low-chlorophyll sea of the study site. Results are compared to measurements from the humid marine setting of the Great Barrier Reef, Australia.