A team of international scientists has announced the discovery of the Taam ja’ Blue Hole (TJBH), a massive marine sinkhole located in Chetumal Bay, on the eastern coast of the Yucatán Peninsula, Mexico. The findings, published in Frontiers in Marine Science, confirm that this underwater structure is now recognized as the second-deepest blue hole ever documented in the world.
Researchers found that TJBH reaches a depth of 274.4 meters below sea level, second only to the Dragon Hole in the South China Sea, which remains the deepest known. According to the team, this discovery offers new insights into submerged karst formations in tropical estuarine environments—areas that have long remained largely overlooked by marine scientists.
The blue hole features an almost circular opening covering approximately 13,690 square meters, or about 1.4 hectares, with an underwater volume reaching nearly one million cubic meters. The walls of TJBH are extremely steep, with some sections sloping at more than 80 degrees.
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Beyond its extreme size, the research team also recorded unusual physical-chemical characteristics within the water column. Near the entrance, at around 5 meters depth, they detected sharp gradients in temperature and salinity—almost 5°C per meter and 10 PSU per meter, respectively. Water stratification inside the hole forms a hypoxic layer at 5–20 meters, a chemocline at 50–80 meters, and a fully anoxic layer at depths greater than 110 meters.
“This type of extreme environment makes blue holes a unique natural laboratory for studying geochemical and microbiological processes,” the team wrote in the publication. Such conditions may also preserve important paleoclimatic records, offering clues to environmental changes in the distant past.
Along the walls of the hole, the researchers documented biofilm layers, sediments, limestone formations, and gypsum ledges. Several organisms—including small worms, mucous filaments, and barnacle remnants—were found in shallow sections, though no pelagic fauna were observed during the survey.
The scientists added that the discovery of TJBH highlights the possibility that many underwater karst formations remain unmapped, especially in enclosed coastal areas such as bays and estuaries. They encourage further exploration to uncover the ecological and geological potential hidden within these environments. This finding marks an important reminder that tropical shallow seas still harbor major geological mysteries—some perhaps as deep and complex as the world’s largest blue holes.
The research on the Taam ja’ Blue Hole was published in an article titled “First insights into an exceptionally deep blue hole in the Western Caribbean: The Taam ja’ Blue Hole (TJBH),” authored by Jaime A. González-Cano and an international research team. The study appeared in the journal Frontiers in Marine Science in 2023. (Sulung Prasetyo)
