Plankton: the world’s most important lung
When thinking of the “lungs of the world”, everyone spontaneously thinks of the tropical rain forest; but that’s not giving our oceans any credit. The fact is, plankton is our most important source of oxygen. This is only one of the reasons why it is so important to examine plankton and understand how this diversity of microorganisms works. It was with this objective in mind that a large international team of scientists, including Jeroen Raes (VIB/KU Leuven/Vrije Universiteit Brussel), was involved in the Tara Oceans expedition. The schooner Tara left for an around-the-world voyage between 2009 and 2013. During this trip, the scientists collected and analyzed thousands of samples from our oceans. The first results will be published in a special edition of Science on May 22.
Jeroen Raes (VIB/KU Leuven/ Vrije Universiteit Brussel): “This project was a big adventure from the very beginning, something that I wouldn’t want to miss for all the money in the world. Initially there was no budget, but we persisted - and in the end got these fantastic results. Within this gigantic collaboration Gipsi Mendez and Karoline Faust of our lab, in collaboration with scientists from CNRS and ENS, focused on the interactions between planktonic organisms. Samuel Chaffron investigated together with scientists from EMBL how plankton is affected by its environment.”
Eric Karsenti, Director of Tara Oceans (EMBL and CNRS): “Thanks to the excellent collaboration between international teams of scientists, Tara Oceans delivered ground-breaking results that will be important for studying oceans and climate change in the future. One of the goals of this adventure was also to show people how important oceans are to our well-being.”
Plankton: a diversity of organisms
Thanks to Tara Oceans, scientists have a good idea of plankton’s impressive biodiversity. Tara Oceans will also make available to scientists worldwide a database with material from more than 35,000 various types of micro-organisms. The DNA of these organisms was charted, and analyses point to the presence of more than 40 million genes, a large number of which were previously unknown.
The dynamics of the marine ecosystem
Using the latest in computer models, the investigators could predict interactions between the organisms in the plankton. These predictions were confirmed under the microscope.
Jeroen Raes: “We discovered that the ocean is a complex ecosystem of interacting organisms – from viruses to small animal larvae. By working together, they form a complicated food chain that gets CO2 from the air and stores it in the ocean floor. We also found out that parasites and viruses greatly affect the composition of the ecosystem. Figuring out these interactions is the first step towards a better understanding of the dynamics and structure of the worldwide marine ecosystem.”
Jeroen Raes: “It’s an amazing moment when you check a computer prediction under the microscope and see that you had it right – that’s a tremendous rush for a scientist.”
Influenced by the environment
Determining how environmental factors such as temperature, pH, nutrients, etc. influence the microscopic organisms in our oceans was another challenge. The Tara Oceans team was able to demonstrate, in those depths that are still penetrated by sunlight, that temperature is the factor that most impacts the composition of the marine ecosystem. This information is very relevant for future climate change research.
Jeroen Raes: “This expedition yielded many new scientific findings. But we are well aware that we have only just begun our exploration of a whole new (underwater) world.”
A laboratory on a boat: a new experience
In addition to being a scientific adventure, Tara Oceans was also a unique experience for scientists who were on board during the expedition. We discovered magnificent landscapes, weathered storms and lived together with a 15-member crew (half of them scientists). Working in the laboratory on the boat (about 3m² in size) was not only a challenge due to the limited space, but also because of the less than stable ground.
Lima-Mendez, Faust, Henry et al.
Top-down determinants of community structure in the global plankton interactome.
Sunagawa, Coelho, Chaffron, et al.
Structure and Function of the Global Ocean Microbiome.
De Vargas, Audic, Henry, et al.
Eukaryotic plankton diversity in the sunlit global ocean.
Villar, Farrant, Follows et al.
Environmental characteristics of Agulhas rings affect inter-ocean plankton transport.
Brum, Ignacio-Espinosa, Roux et al.
Global patterns and ecological drivers of ocean viral communities.
Take a virtual tour of the boat
Expedition information and images
International press release (pdf)