Like the voyages of a hundred or two hundred years ago, the Tara Pacific voyage lasted two years. Purpose: to investigate the conditions of life and survival of corals. The ship crossed the entire Pacific Ocean, collecting the largest gene pool conducted in any ocean to date.
Photo credit: University of Konstanz
The team’s 70 scientists from eight countries took about 58,000 samples from a hundred reefs that were studied. The first results of the analysis have now been published in Nature Communications. The most extensive collection of coral reefs is freely available and, for years to come, will be the basis for integrating the characteristics of corals and finding them a way to survive the climate.
The first important result of the expedition: Global biodiversity is much higher than previously thought. The effect of environment on evolution depends on species. And, genes important to corals are reproduced.
Global Biodiversity Ten Times Higher Than Thought
Reefs are oceans that contain some of the world’s most diverse ecosystems. Although they make up only 0.16 percent of the world’s oceans, they contain about 35 percent of known marine life. Using a genetic marker-based dataset, the researchers found that all the world’s bacterial species are already present in coral reefs. “We have been underestimating the diversity of the world”, says Christian Voolstra, professor of genetics of adaptation in aquatic systems at the University of Konstanz and scientific coordinator of the Tara Pacific expedition. It is estimated that the current number of different species of life (about five million bacteria) is decreasing by about 10.
Impacts of Environment on Evolutionary Adaptation and Species-Species
The 32 island groups under study act as natural ecosystems and provide diverse ecological environments, allowing for the analysis of the relationship between environment and genetics at large spatial scales. This led to another important discovery: the effect that the environment has on the evolution of corals varies by species. To find out, researchers looked at telomeres, the ends of chromosomes that carry genetic information, for the first time.
In humans, telomere length decreases throughout life, the more cells divide, meaning that natural age is closely related to telomere length. Researchers on the Tara Pacific expedition have now found that the telomeres in corals that cope with stress are always the same length. “Apparently they have a way of maintaining the length of their telomeres”, Voolstra concludes. In the most vulnerable coral species, which also have a short life span of about a century, telomere length correlates with environmental stressors, such as temperature fluctuations. “The direct impact of environmental stress on the fitness of an organism can also affect human health”says Voolstra.
Essential and Duplicated Genes
Research from the Tara Pacific Expedition has shown that the longevity of some coral species may have another reason: the duplication of certain genes. Many important genes are found multiple times in the genome. The researchers were able to find this out by sequencing coral genomes using a new high-resolution technique. This method, called long-term sequencing, makes it possible not only to know the type of genes present, but also to look at their order in the genome. According to Voolstra’s book, the high rate of gene duplication may be the reason why corals can live for thousands of years even when exposed, for example, to high levels of UV radiation in shallow water.
The Tara Pacific expedition, named after the research vessel, will provide the basis for a large-scale assessment of the diversity of coral reefs for years to come. What also makes this program unique is that the samples were collected in several locations and over several years. The researchers examined the corals at each site in the same way, resulting in the same results.
All Data Collections Available Free of Charge
All data sets are publicly available and fully described with physical and chemical parameters to provide them as a scientific tool for all researchers. “This is special”, Voolstra says. “It’s the largest collection of coral reef material ever collected and it’s completely open.” His hope is that this data collection will be the foundation and research to guide future research on coral reefs around the world for many years to come.
Source: https://www.uni-konstanz.de/en/
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