There are currently two types of causes of ocean blue holes, namely limestone caves and coral reef growth structures.
Limestone caves were formed by lowering sea levels during the Ice Age, when the limestone dissolved and developed into large cavities in the lower part . As the dissolution cavities became larger and larger, the top collapsed. A large hole with a steep edge is called a sinkhole. At the end of the Ice Age, sea levels rose and seawater filled the sinkhole, which became the blue hole everyone sees. The type of coral reef growth structure was proposed in the late 1990s, the most typical being the Hautman-Abrolhos coral reef blue hole, located on the southwest outer shelf of Australia. Since the Holocene, 10,000 years ago, the coral reefs of this areadeveloped rapidly. Many smaller, fast-growing reefs formed spine-like protrusions and came together to eventually form a roughly circular hole.
The depths of the blue hole are low-oxygen or anoxic environments, and there is a lack of sunlight. The mechanism that supports the existence of marine life has yet to be explored, particularly microbial and microbial communities. genes under anoxic conditions, which deserve to be explored.