The rainforest of the oceans
Expedition to the Pacific Ocean
The Tara left France on 28 May 2016 and sailed throughout the Pacific Ocean for more than two years. The team’s route took them from the Panama Canal to Japan and from New Zealand along the coast of China to Canada. The Tara travelled a total of 100,000 km, across eleven time zones, visiting 40 archipelagos along its way. The ultimate purpose: to understand and document corals and their livelihood in the Pacific.
Each and every factor and environmental condition that may affect coral were to be documented by the Tara Pacific Expedition in order to understand their effects: all the symbiotic relationships between corals and their associated (micro-)organisms, as well as all the plant and animal species that the corals provide a habitat for, even the temperature and chemical composition of the water was documented.
The ship
The Tara is a schooner with a particularly flat stern – particularly well suited to travelling across coral reefs without damaging them. During the Tara Pacific Expedition, the vessel was home to a total of 70 scientists from eight different countries. One of the crew’s leaders was Professor Christian Voolstra, Professor of Genetics of Adaptation in Aquatic Systems at the University of Konstanz.
Pioneering spirit
“It was a dream come true”, Christian Voolstra reflects on the monumental expedition. Up to this point, there had not been such an all-encompassing survey of the living conditions for coral. During the two-year project, Christian Voolstra was able to dive places previously untouched by humans. He saw corals that were bigger than a house and older than 10,000 years. He swam with sharks and collected data in the Pacific’s reefs that will form the basis for decades of research.
At the same time, he encountered a nightmare: He saw entire coral reefs killed by climate change. He witnessed how a third of all existing coral disappeared in less than three years. Instead of giving up, he redoubled his research efforts: to understand the living conditions of coral and to find a way for them to survive climate change.
His largest task is still to come: “Each hour in the water means 100 more hours in front of the computer”, Voolstra says. After the expedition is over, the actual research work starts: All the samples collected need to be analyzed scientifically using the most modern techniques.
Coral, a natural born “multiplayer”
Corals are anything but loners. Instead, they are so called metaorganisms comprised of many symbiotic member species. Corals engage with photosynthetic algae that provide nutrients and energy. They associate with microorganisms and bacteria that play an important role in their metabolism and gene expression. Corals provide a habitat for countless plant and animal species, benefitting in turn from their lodgers. “Hundreds of thousands, if not millions, of species, most of whom have not yet been described, are part of the coral metaorganism community – and that’s not even counting the bacteria”, Christian Voolstra says. “Corals are true multiplayer organisms”.
“Life depends on symbiosis”, Voolstra explains. Corals are specialists for engaging in symbiotic relationships. They are exceptionally adaptive as a result of the flexibility of the holobiont network, driven by environmental factors. “Corals are extremely well-adapted to existing environmental and climate conditions. They use their ecosystem extremely efficiently and are real powerhouses”, says Voolstra. This high level of specialization to their environments is what makes corals so successful but also highly vulnerable: They are extremely sensitive to even smallest changes to their prevailing environmental conditions.
Just one degree Celsius
The colour of death is white for coral. “Coral bleaching” is a severe phenomenon, named after the color corals take on before they die. The cause of coral bleaching is warming ocean waters. As the water temperature rises, the symbiotic photosynthetic algae inside the coral cells that are essential for their survival are lost. Without these algae, coral do not obtain nutrients from photosynthesis. “Corals basically starve to death”, Voolstra describes. “They turn a pale, whitish colour, caused by loss of their photosynthetic algal symbionts, and eventually die of hunger”.
Extent of coral extinction
An increase of the water temperature by merely one degree Celsius is enough to cause coral bleaching in some regions. Even the most optimistic climate change projections project a global temperature increase of at least 1.5 degrees Celsius. That would be enough to cause almost total extinction of corals worldwide.
“Our generation must solve the issue of climate change.”
Nonetheless, Christian Voolstra remains optimistic about humanity having a chance to save the coral reefs: “We live in the most exciting time ever: before now, we did not have the scientific methods to do something. Now we have that chance. Our generation must solve the issue of climate change”. The Tara Pacific project will do its part. Christian Voolstra and his team would like to use the samples from the Pacific Ocean to find out what it takes to make corals the coming century and beyond.
