Pacific Ocean coral reefs reveal millions of types of bacteria

Coral reefs are increasingly becoming an object of study for scientists. In 2016. The Tara Pacific Expedition program was launched, with an international team of scientists collecting samples of three types of coral, two species of fish and plankton from each of the 99 coral reefs in the Pacific Ocean. The Tara ship has covered more than 100 thousand. km, making about 3,000 dives. As a result, the crew collected more than 60,000 samples for advanced molecular and biogeochemical analyses. The goal of the expedition was to reveal new aspects of biodiversity that coral reefs have in the face of ongoing climate change. The scientific expedition ended in 2018. and after five years of analysis and waiting for research results, Tara Pacific is sharing the results of its expedition. The results shed a whole new light on the biodiversity of coral reefs and the Earth.

a

Coral reefs with nearly 3 million varieties of bacteria

The schooner of the Tara expedition reached the most isolated coral reefs in the southern Pacific Ocean and the most urbanized coastal areas of Asia, not forgetting the Coral Triangle (located between the Philippines, Indonesia and Malaysia). The area of the Pacific Ocean, where more than 40% of the world’s coral reefs are located, has never before been surveyed on this scale. The 32 archipelagos visited by the Tara Pacific Expedition presented a wide range of environmental conditions in terms of temperature, acidification and reef health, being a huge source of data. Scientists studying coral have calculated that coral reefs from the Pacific Ocean may harbor at least 2.8 million types of bacteria. This figure suggests that there are essentially more bacteria on the planet than previously thought.

Coral reefs and climate change

Coral reefs are the most diverse ecosystems on Earth. It is predicted that the bacteria they harbor may help corals obtain the nutrients they need to survive or protect themselves from disease. “The huge diversity of microorganisms on reefs can provide ecological insurance for corals, fish and other inhabitants. If some bacteria have similar functions, then one bacterium that does not survive due to environmental conditions could potentially be replaced by another,” said Pierre Galand, a scientist at Sorbonne University in France and co-author of the Tara expedition study. “The high diversity of the reef microbiome may therefore be important because it can help mitigate environmental perturbations. This will be the subject of future research.”

However, this underwater ecosystem is extremely sensitive to temperature fluctuations and water pollution that result from climate change. Coral reefs, exposed to prolonged stress caused by elevated water temperatures, fade and die. They then lose symbiotic algae, causing the death of the entire colony. Environmentalists regularly warn that coral reefs are in poor condition and that they may soon be in danger of total degradation. With the threat of coral reefs disappearing from the Earth, it is important to conduct research and expand knowledge about these fragile ecosystems.

a

Tara Pacific Expedition project – revealing a new aspect of coral reef biodiversity

The Tara Pacific expedition has helped to present new insights into the diversity of coral reef ecosystems. During the expedition, the crew collected coral samples in a systematic manner and following the same protocol at multiple locations and over an extended period of time – corals at each site were examined in an identical manner, making the results comparable. Tara scientists have shown that compared to other environments, coral reefs are much richer in microflora, and that the world’s microbial biodiversity is largely underestimated.

Tara’s latest research on coral reef biodiversity provides material for large-scale analyses of coral ecosystem diversity. They make it possible to structure and manage data at ecosystem scale. Tara’s scientific expedition is the largest study of coral genotypes conducted to date. Tara Pacific wants to make the data collected during the expedition available to a wider audience and make it publicly accessible to all interested parties. Scientists believe that this will increase the desire to protect coral reefs, that the need to take care of them will be better understood by global communities. “After our initial observations, it seems clear that the future state of coral reefs will depend on the climatic trajectory and our ability to locally protect reefs from local practices and pollution,” – said Serge Planes, scientific director of the Tara expedition.

Photo author: Katarzyna Banaszak