We’ve been drastically underestimating Earth’s microbial diversity

A two-year expedition across the Pacific has revealed that the microbes present in coral reefs there can be as diverse as the microbiomes of other ecosystems on Earth combined. This could mean that we are significantly underestimating the overall microbial diversity on Earth.

Coral reefs make up less than 1 percent of the ocean, but are home to nearly a third of the marine flora and fauna. The expedition, launched in 2016 and led by Serge Planes of the University of Perpignan in France, visited 99 reefs in the Pacific Ocean. Plains and his colleagues took water samples from each reef and sampled three types of coral and two types of fish.

They sequenced a significant portion of DNA from the bacteria and archaea present in the samples. Out of the approximately 3 billion resulting sequences, over 500,000 unique sequences were found, demonstrating the vast diversity of microbes. Different microbiomes were also present in samples taken from different locations in the ocean.

“Coral diversity is reflected in microbiome diversity,” says Pierre Galland of France’s Sorbonne University.

Extrapolating these results to the microbiomes of hundreds of other coral species and thousands of fish that live on Pacific reefs, the researchers say, the total microbial diversity on the reefs is enormous. there is All those reefs will be almost six times as high. They say this could be larger than some estimates of global microbial biodiversity.

Such microbial diversity plays an important role in coral reef ecosystems. For example, some corals have symbiotic relationships with bacterial species. Other microbes facilitate nutrient cycling or protect against pathogens.

“Microbes are involved in so many different processes that they actually run these ecosystems,” says Deron Birkepyle of the University of California, Santa Barbara.

But it’s unclear how microbiomes will be affected by factors such as rising temperatures due to climate change, ocean acidification, and overfishing that are causing the loss of reef macrodiversity, Plains said.

“There is currently no direct link between coral reef decline and microbiome changes,” he says. “It’s largely because we know so little about the microbiome.”