Hypercapnic Hypoxia in Mangroves
Why in News?
A study published in AGU Advances analyzed 23 global mangrove sites, revealing most already face mild (34-43% of time) or severe (6-32%) hypercapnic hypoxia, amplified by low tides and warming.
Definition
- Hypercapnic hypoxia combines hypercapnia (elevated CO₂) and hypoxia (low oxygen), creating chemically hostile water conditions.
- It peaks during low tide when water circulation slows, especially in low-salinity, tropical estuaries.
Causes
- Rising atmospheric CO₂ from climate change dissolves into waters, while warmer temperatures reduce oxygen solubility.
- Low tides trap respired CO₂ and deplete oxygen via microbial activity and limited mixing.
- Tropical mangroves experience it twice as often as subtropical ones due to higher heat.
Impacts
- Reduces habitat quality in mangrove fish nurseries, shifting species toward smaller, tolerant ones and declining large reef-associated fish.
- Threatens biodiversity, fisheries, and livelihoods for millions in developing coastal nations.
- By 2100, 78% of sites may see stressful conditions lasting 12-24 hours consecutively under extreme scenarios.
Mangrove Role
- Salt-tolerant trees/shrubs in tropical/subtropical intertidal zones, acting as buffers against erosion and nurseries for marine life.
- Highly productive but vulnerable ecosystems now facing compounded climate stressors.
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