The Tara Oceans Expedition has now come to an end after a 115,000 km round-the-world voyage lasting two and a half years. Under the scientific leadership of Dr. Eric Karsenti from the European Molecular Biology Laboratory in Heidelberg, the expedition has collected a unique quantity and diversity of samples and data about marine plankton. The purpose of this international project is to carry out morphogenomic analyses and obtain detailed insights into the interaction and evolution of marine plankton from the perspective of climate change and to develop dynamic models for the coevolution of these ecosystems and the hydroclimate.
The international Tara Oceans Expedition ended on 31st March 2012 in the Breton harbour of Lorient, from where the schooner Tara had set sail on 5th September 2009. During its 938 days at sea, the expedition covered more than 64,000 sea miles (115,000 km) and took more than 27,000 marine samples at 150 locations in the Mediterranean Sea, the Indian, Pacific and Atlantic Oceans and the Antarctic. 126 scientists from 35 countries spent two and a half years on the Tara collecting and analyzing marine plankton, and it was the largest and most comprehensive study of marine plankton that has ever been undertaken. Marine plankton are at the base of marine food chains, and affect the global climate and the geochemical substance cycles on the Earth. The expedition has discovered 500,000 new microorganisms, and analysis of the scientific data has only just begun.
Dr. Eric Karsenti, senior scientist at the European Molecular Biology Laboratory (EMBL) in Heidelberg, is the scientific director and co-director of the Tara Oceans Expedition. Together with Etienne Bourgois, owner of the ship and president of the Tara Foundation, Karsenti brought together and coordinated a unique team of researchers, including molecular and cell biologists, bioinformaticians, ecologists, taxonomists, microbiologists, oceanographers and physicists, acquired the necessary funding and determined the major goals of the expedition:
In addition to coordinating the expedition, Karsenti works with an EMBL group led by Jan Ellenberg whose goal is to develop high-throughput imaging methods for protists (unicellular organisms) and small metazoans (multicellular organisms). He also works with Detlev Arendt on the biogeography and evolution of marine annelids (bristle worms). Peer Bork and his group of researchers participate in the project by contributing genome analyses and developing the expedition database.
Tara Oceans is not the only research project aimed at sampling the microscopic world in the Earth’s oceans. There is also the Sorcerer Expedition led by Craig Venter and the international “Census of Marine Life” which has been ongoing since 2000.
What makes Tara Oceans unique is the expedition’s holistic approach: the investigations focus on organisms that are less than 100 nanometres in size as well as fish larvae that are a centimetre or more in size – this represents a difference of five orders of magnitude, i.e. the size difference between a mouse and an elephant.
Virus es and bacteria were collected by filtering seawater through Millipore filtres with different pore sizes; the protists and zooplankton were caught with nets of varying mesh widths. Water was sampled from the surface of the sea as well as from depths of 1,000 metres, thus including so-called mesopelagic or twilight zone areas in which photosynthesis is not possible, but which are still frequented by planktonic organisms on their daily vertical migrations. The researchers also recorded physical and chemical parameters: temperature, salt content, pH, sea currents, etc. Another unique aspect of this large-scale project is the combination of genome analyses (high-throughput sequencing) and state-of-the art imaging (high-throughput imaging). The researchers envisage that these methods will help them to discover relationships between the genome and organisms and between ecosystems and evolution and contribute to the development of eco-morphogenetic models that help predict how marine life will evolve in response to climate variation.
Eric Karsenti’s original field of research at EMBL has little in common with marine research. His research group is mainly focused on research into how the mitotic spindle forms, the organization of the microtubules during the division of eukaryotic cells, and the biochemistry of the signalling pathways involved. This research is still ongoing, but Karsenti himself has devoted the last four years to the organization and coordination of the Tara Oceans Expedition and concentrated on marine research. He says about himself: "I have always been fascinated by the sea, and as a young student I wanted to be a marine biologist. Things did not turn out exactly like that, and I started a career in cellular and molecular biology. Tara Oceans is a new adventure for me. At 60, I feel the need for a change of pace, to address exciting and disturbing questions concerning the past evolution of our planet and its future. And of course, it is the ocean that concerns us all, because the ocean gave birth to life and life on earth still depends on it. I also felt the need to go to my fellow human beings to share the great adventure of breakthrough in scientific understanding of our universe, because science is not only technology but also a source of wisdom.“ This is the actual mission of the Tara Oceans Expedition.
The 120 t schooner Tara, which is stuffed full of state-of-the-art scientific equipment and has taken the scientists on a two-and-a-half-year voyage around the world, is a very unusual boat. Built in 1989 for the French adventurer and polar researcher Jean-Louis Etienne, the ship was previously used for several expeditions to the Antarctic and Spitzbergen. In 1999, the ship was acquired by the late Sir Peter Blake, a well-known New Zealand sports sailor and winner of many high sea regattas. Renamed “Seamaster”, the schooner was used for expeditions under the auspices of the United Nations Environment Programme. Blake was murdered by river pirates during one of these expeditions into the Amazon in Brazil. In 2003, the fashion queen Agnès Troublé from Paris and her son Etienne Bourgois, director of the fashion and cosmetics company ”agnès b.“, bought the ship.
Renamed Tara, the ship was used for a number of expeditions into the Arctic and Antarctic to investigate the interaction of air, sea and ice. It was also used for expeditions and training programmes to raise public awareness of environmental and climate protection. Etienne Bourgois talks about his commitment to the expeditions and what motivated him to work with Eric Karsenti on the Tara Oceans programme:
“Tara Expeditions was born from a great desire of keeping faith. It is a collective quest to understand what is happening climate-wise and to explain it in simple terms. When we acquired Tara in 2003 to create the Tara Expeditions project, the environmental approach, initiated by a company leader was still quite a marginal gesture. Thank goodness, things have evolved. Today I do not feel like a radical ecologist. I believe we need to live with our contradictions and attempt to resolve them. It really has to do with a revolution in our mentalities. To act in ecology we shall have to relinquish our individualist world. It is the key. This is what we attempted and accomplished on Tara. A team’s work at the service of the planet. This exceptional ship must pursue her mission as ambassador of the world’s citizens, must remain a catalyser of energy and desire to tackle without glitter the main question that arises for each one of us: What future are we preparing for our children?”
Karsenti E, Acinas SG, Bork P, Bowler C, De Vargas C, et al. (2011) A Holistic Approach to Marine Eco-Systems Biology. PLoS Biol 9(10): e1001177. doi:10.1371/journal.pbio.1001177