[Reading Science] 'Endangered' Coral Reefs, Struggling to Survive Underwater?

Pacific Coral Reefs Exhibit Genetic Diversity Over 10 Times That of the Indian Ocean

Genetic variation in coral reefs inhabiting the Pacific Ocean has been found to be much more diverse than in other seas. This finding draws attention to the potential use of such diversity in ecosystem conservation efforts to respond to climate change, including saving coral reefs that are threatened with extinction due to rising sea temperatures and marine pollution.

▲Adhered Tree Coral. [Photo by Korea National Park Service]

A research team from Sorbonne University in France published these findings on the 1st in the international academic journal Nature Communications. The team conducted field surveys while sailing approximately 100,000 km across the Pacific Ocean, starting from Lorient, France in May 2016, passing through Papua New Guinea, Japan, Indonesia, and other locations. They collected and analyzed over 58,000 samples of seawater, coral reefs, fish, plankton, and more from a total of 249 sites.

The research confirmed that coral reefs living in the Pacific Ocean possess far greater genetic variation than those in other seas. They analyzed 16S ribosomal RNA from about 5,000 samples. The 16S ribosomal RNA is a component of ribosomes, the cellular organelles that produce proteins, and is a molecule found in all bacteria. Since the nucleotide sequences of this gene differ among bacterial species, it can be used to distinguish types. As a result, the team achieved the remarkable outcome of identifying 542,399 distinct DNA nucleotide sequence variants (amplicon sequence variants, ASVs). Compared to previous studies in the Indian Ocean, where about 44,000 ASVs were observed, this is more than ten times greater. It is estimated that the total ASVs of all bacteria and archaea on Earth range from at least 2.72 million to as many as 5.44 million, with over one-fifth of these existing in coral reefs beneath the Pacific Ocean.

Based on this, the research team estimated that the ASVs of coral reefs worldwide exceed approximately 2.8 million, suggesting that the diversity of microbial species on Earth is far greater than previously estimated. The team also hopes to use these results to clarify how species diversity affects the function and health status of coral reefs, including the impacts of climate change and marine pollution.

Meanwhile, coral reefs worldwide are rapidly disappearing due to changes in sea temperature caused by global warming and marine pollution. The area of coral reefs has decreased by more than half over the past 70 years, and species diversity has declined by about 60%.