From UPSC perspective, the following things are important :
Prelims level : Yongle Blue Hole (YBH)
Mains level : Signifcance of Blue Holes
Carbon more than 8,000 years old has been found inside the world’s deepest blue hole — the Yongle Blue Hole (YBH).
Yongle Blue Hole (YBH)
- The deepest known marine cavern is the Yongle blue hole, which measures roughly 300 metres from top to bottom.
- Blue holes are marine caverns filled with water and are formed following dissolution of carbonate rocks, usually under the influence of global sea level rise or fall.
- Its waters are mostly isolated from the surrounding ocean and receive little fresh water from rainfall, making it a rare spot to study the chemistry of oxygen-deprived marine ecosystems.
- What distinguishes them from other aquatic caverns is that they are isolated from the ocean and don’t receive fresh rainwater.
- They are generally circular, steep-walled and open to surface.
Significance of YBH
- YBH has a depth of 300 metres, far deeper than the previously recorded deepest blue hole, Dean’s Blue Hole in Bahamas, which had a depth of 202 metres.
- However, like most blue holes, it is anoxic i.e. depleted of dissolved oxygen below a certain depth. This anaerobic environment is unfavorable for most sea life.
- Such anoxic ecosystems are considered a critical environmental and ecological issue as they have led to several mass extinctions.
- Concentrations of carbon, usually found in deep marine holes like YBH, provide a natural laboratory to study carbon cycling and potential mechanisms controlling it in the marine ecosystem.
- The transition from aerobic to anaerobic environment adversely affects the biogeo-chemistry of the ocean.