2023-05-08 17:30:08
Serge Planes is research director at the CNRS and specialist in the genetics of marine organisms and the ecology of coral reefs. He was also scientific director of the Tara Pacific expedition.
You coordinated the research during the Tara expedition, this famous scientific mission by sailboat which is reminiscent of the Deep Life project. Why is this type of expedition necessary to advance research?
Expeditions like Tara or Deep Life allow you to focus on a scientific question for several months, even several years. This is not possible with national oceanographic fleets, since, in this case, we rent a boat for a month, which limits our ability to intervene in the environment studied. On the contrary, these long missions make it possible to apprehend the scientific question on a larger spatial or temporal scale. You can’t do it any other way today.
According to many scientists, knowledge about coral reefs still has many gaps. What difficulties does research encounter in making progress in these environments?
Until now, beyond 50 meters depth, the main means of observation were what are called “ROVs” (for Remote Operated Vehicles), i.e. say small robots or small submarines which made it possible to obtain direct visual or by camera of this environment. The establishment, in recent years, of structures that allow diving into mesophotic environments [à des profondeurs comprises entre – 30 mètres et – 150 mètres] opens the prospect of apprehending by the human eye, by hand – which remains more precise – the diversity of these ecosystems.
These reefs face many threats. With the rise in ocean temperatures, in particular, how will our corals evolve in the years to come?
There is no certain answer, as we still have several unknowns. We can nevertheless affirm that we are in a period of regression in the distribution of coral reefs. This decline is mainly due to global warming. The underwater heat waves that it causes in turn lead to massive bleaching and mortality in certain places. This situation is not systematic: there are families of corals much more resistant than others. But what is clear is that this divergence in the fragility and vulnerability of the different families will lead to changes in the coral ecosystem. As a result, the visual of the coral reef, its composition and its morphology will probably change in the years to come. This will be accompanied by losses of diversity, with a significant decline of certain large families that are less resistant, not to mention extinction.
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