The epic journey discovers astonishing microbial diversity among coral reefs

In the largest study of Pacific Ocean corals, researchers have found that there is likely to be more genetic diversity among the world’s corals than previously thought.

The assessment is based on a collection of studies reporting the results of the Tara Pacific Voyage, the ship’s two-year research cruise. Tara, It studied the genetic, chemical and microbial diversity of coral reefs. Analysts estimate that More than half of the world’s coral reefs 60% of associated species diversity has disappeared in the last 70 years.

On 28 May 2016 marine scientists, microbiologists and crew members embarked on a 100,000 kilometer journey from the port of Lorient in France. They collected 58,000 samples of water, aerosols, coral, fish and plankton from 249 locations, including Indonesia and Japan. and Papua New Guinea.

In a study published in Natural communication¹, marine microbiologist Pierre Gallant of the Sorbonne University in Paris and his colleagues sequenced a gene commonly used to identify and classify microbes from 5,000 samples. This is called the 16S ribosomal DNA marker gene. The team identified 542,399 DNA sequences called amplicon sequence variations (ASVs), a measure of genetic variation in bacteria.

Gallant says he was surprised to see half a million views in one place. compare, According to an existing estimate, 44,000 ASVs are associated with Indian Ocean coral reefs. „As we continued to sample, we continued to see more diversity and more bacteria,” Gallant says.

The authors state that their data from the Pacific represent one-fifth of the known estimate for the diversity of all bacterial and archaeal communities on Earth (between 2.72–5.44 million ASVs).

Researchers estimate the diversity of reefs worldwide at about 2.8 million ASVs. This suggests that the known value for the diversity of all Earth’s microbial communities may exceed existing estimates, says Serge Plains, a marine ecologist at PSL University in Paris and head of the consortium.

The scientists say they will use the latest results to tease apart how that diversity links to reef function and health, including the impacts of climate change and pollution.

Vitamin 'B’ for bacteria

Another study, too Natural communication Examines the genetic and molecular structure of a type of bacterium commonly associated with coral reefs. The study aims to understand the benefits bacteria can provide, such as helping corals obtain vitamins and amino acids.

Corentin Hochardt, a PhD student at the Sorbonne University, studied three types EndozoicomonadaceaeA family of bacteria commonly associated with corals to better understand what role bacteria play in coral health and function.

The researchers sequenced bacterial genetic material in samples from three coral species, Pocilophora (Cauliflower Corals), Porites (Stony Corals) and Millebora (fire corals), collected from 99 reefs in the Pacific Ocean. their studies³ found that each species of coral is associated with a distinct species Endozoicomonadaceae. This suggests that corals have developed a strong relationship with their bacteria over time and that bacteria are beneficial to corals, says Gallant, who was also involved in the study.

The study found that each bacterial species produces a different array of vitamins and amino acids that may play important roles in coral health and immunity.

The researchers also collected data that allowed them to examine interactions between physiological signs of stress and factors such as water quality and temperature in coral and microbial communities.

„With answers [to those questions]”You can dissect what climate change and anthropogenic pressures will do to the future of coral reefs,” Plains says.

Shipping news

Tara Pacific’s 100,000-km research expedition is one of a relatively small number of maritime scientific expeditions of this scale and ambition.

Scientists collected samples during about 3,000 dives, with teams rotating every six to eight weeks.

The ship had a laboratory to analyze physical and chemical parameters of water samples such as temperature and pH. Coral and fish tissue samples were frozen and stored on board, then sent to onshore laboratories for genetic sequencing and analysis every six months.

The expedition was supported in part by the Tara Ocean Foundation – founded in 2003 by Agnes Trouble, a French fashion designer known as Agnes B, and her son Étienne Bourgois – to research and explore the ocean. The airlines say the trust provided the consortium with the ship and five million euros (US$5.4 million) for internal costs such as fuel and staff salaries.

Other funders are France’s National Research Institute (ANR) in Paris and Genoscope, the French National Sequencing Center in Évry.

The consortium is still analyzing data from the trip. Planes expects another batch of papers to be published next year examining what changes are causing coral biology and physiology and how those changes affect the reef ecosystem.