Press release – 06/09/17
Having set out in May 2016 to cross the Pacific Ocean, Tara recently reached the halfway point of the expedition dedicated to coral reefs. The schooner has already visited 15 countries and sailed nearly 50,000 km from east to west. This major mission, initiated by the Tara Expeditions Foundation, has enabled scientists to collect more than 15,000 samples so far, in the course of nearly 2,000 dives. Analysis of the samples has just started and will lead to a better understanding of coral reef biodiversity, their state of health and ability to adapt to climate and environmental changes. The scientists aboard Tara have observed global coral bleaching across the Pacific Ocean: in some sites, close from 30% to 90% of coral cover was impacted. Tara Pacific is supported by the CNRS, CEA, CSM and PSL Research University, as well as many other public and private partners.
© Francis Latreille – Tara Expeditions Foundation
Tara departed from Lorient, her home port, in May 2016, and to date has sailed half of the 100,000 km of the Tara Pacific 2016-2018 expedition. While crossing the Pacific Ocean from east to west during the first year of this campaign, Tara reached the most remote coral reefs in the South Pacific. Scientists aboard have collected 15,000 out of a planned 35,000 samples. Analysis of these samples will give us a better understanding of how coral biodiversity faces environmental changes.
Upon arrival at Ducie Island (British Overseas Territory), located west of Easter Island in November 2016 and then in Moorea (French Polynesia) the following month, Tara’s crew observed the first reefs strongly impacted by global warming.
Tara witnessed many episodes of massive coral bleaching
The mission focuses primarily on coral’s biological responses to current environmental disruptions and several observations were made by Tara’s crew:
• In Polynesia, bleaching affects 30 to 50% of coral in some islands of the Tuamotu archipelago,
• At some sites, close to 70% of coral cover is impacted by bleaching. The same observation was made at Pitcairn Islands.
• Wallis and Futuna remain relatively preserved.
• Further north, despite more temperate waters, reefs have not been spared bleaching: for example, 70% are affected in Okinawa, Japan.
In sparsely populated areas with little pollution like Polynesia, the rise in temperature is the only factor responsible for such coral degradation. “The higher the temperature and the longer the exposure to these high temperatures, the more devastating the bleaching” says Serge Planes, CNRS researcher and scientific director of the Tara Pacific mission. The combination of these 2 factors causes the symbiosis between alga and coral to rupture, thus leading to polyp death when a warming period exceeds 3 weeks. According to Serge Planes, “We can no longer speak of one-off or cyclical episodes of temperature rise, like the climatic phenomenon El Niño. Now, the ocean is warming up globally and summer seasons are getting very hot and increasingly closely spaced in time”.
For Romain Troublé, executive director of the Tara Expeditions Foundation, this is proof that “limiting global warming to 2 degrees as enacted in the Paris Agreement is far from being sufficient for marine ecosystems”.
Profound changes of coral reefs in the next decades
“Original data from the Tara Pacific expedition will provide reliable information on which micro-biodiversity factors favor or not the resistance of species” explains Denis Allemand, director of the Scientific Center of Monaco (CSM) and scientific co-director of the expedition. Today, abundant coral species are those for which conditions are ideal. In the future, the environment will become favorable to the development of other species. In the current context of ecological changes, the ability of species to adapt is evolving. This suggests that profound changes in coral reef ecosystems will take place in the next decades.
Bleached coral in the Tuamotu – © David Hannan – Ocean Ark Alliance – Tara Expeditions Foundation
15,000 samples collected
During this first year of expedition, the Tara Pacific team collected close to 15,000 samples from 17 sites to define the microbial diversity associated with coral. The scientific team also tested aboard Tara a new in situ DNA sequencing technique able to identify molecular species. “Thanks to the ‘MinIon’, a sequencer the size of a large USB key, high throughput DNA sequencing is conducted aboard, which is very useful for immediately identifying species in case of doubt. Data analysis enables us to classify collected species by comparing them to those already known” explains Quentin Carradec, Genoscope (CEA).
Coral sample – © Yann Chavance – Tara Expeditions Foundation
In France, the Genoscope teams have begun sequencing the genomes to characterize microbiome diversity – all micro-organisms associated with coral, reef fish or the surrounding sea water. The first sequencing tests reveal samples of very good quality, confirming that the sample preservation and transportation methods used by the Tara team are satisfactory.
Studying microbial life to understand responses to environmental changes
This sample library will allow us to establish a unique database intended for international laboratories brought together by the Tara Expeditions Foundation in the framework of Tara Pacific. In the long term, scientists will be able to compare reefs and distinguish their ability to withstand environmental disruptions, and to check the hypothesis that a rich coral ecosystem with high biodiversity is more resilient. A possible correlation could be established between microbial diversity associated with coral and diversity of coral species. Studies of genetic diversity aim at discovering the genomes of a whole set of organisms cohabiting with and/or around coral and their responses to stress, especially related to global warming.
Tara at the heart of the Coral Triangle for the second part of the expedition
The schooner is now on the Great Barrier Reef and in coming days and months will sail to New Caledonia, Solomon Islands, Papua New Guinea, Indonesia, the Philippines, Palau, China and Taiwan, where researchers will continue the sampling protocol. Tara will cross areas of very rich biodiversity, including some never studied before, particularly in China. Back east, in Clipperton, the scientific teams will focus on marginal coral colonies. In La Paz, they will observe the northernmost corals in the East Pacific. Tara Pacific will then end with the schooner’s return to Lorient in October 2018. More than 100 researchers from 23 international laboratories
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