Second year of Tara Oceans expedition: year of the upwelling

© V.Hilaire/Tara Expéditions

26 August 2010

One thing Dr. Chris Bowler (Expedition Scientific Coordinator and CNRS Director of Research in Biology at the Ecole Normale Supérieure) asserts without any scientific doubt: ‘the star’ of the expedition’s second year will be the study of upwelling off the coast of Peru in the Pacific Ocean.

But before that, two other big scientific ‘moments’ await Tara’s arrival:  In Antarctica, the study of diatoms, the phytoplankton which trap the most carbon dioxide in the world. And in the Galapagos, the study of acidification taking place in that part of the Pacific Ocean. Acidification may be an early indication of our future climate.

In his office at the Ecole Normale Supérieure, rue d’Ulm in Paris, Chris Bowler is surrounded by posters and photographs of microorganisms — not exactly an austere setting. An informal ‘fifteen minutes with a journalist,’ he greets me with coffee and a big smile. The conversation begins.

“The most important upwelling we’ll be studying throughout the whole expedition will be the upwelling off the Peruvian coast – one of the richest plankton sites in the world. A lot of anchovy fishing takes place there since plankton is an important food source for this fish.”

Upwelling is a phenomenon whereby sediments and fish detritus rise to the surface. Driven from the depths by powerful underwater currents, it supplies the plankton with all its staple ‘foods’, such as proteins, fatty acids and carbon.

“These important habitats will undoubtedly provide us with some precious samples. Bear in mind that on this three-year Tara expedition, we are establishing a scientific base-line, ‘time zero’, making an inventory of the situation at the beginning of the 21st century.  So, these results will still be instructive hundreds of years from now.” Chris almost regrets not being able to live long enough to see the results. 

On this second year, during its journey from Cape Town (South Africa) all the way to Auckland (New Zealand) Tara will do soundings in two of the world’s four oceans: the South Atlantic and the South Pacific. In both these oceans, where currents move from east to west forming circles (gyres), the biggest upwellings occur in each case on the East coast of the African or American continent. Another upwelling we will study is the one produced by the cold current which runs along the coast of Argentina rising up from Antarctica. It is very rich in sediments.

Chris turns to a world map on the wall. The line of Tara’s journey has been marked out. “In our crossing of the South Atlantic, we will also continue to study the famous Agulhas Rings.” His hand gestures depict these circles of currents which form in the Mozambique Channel, and which the expedition followed last July up to the Cape of Good Hope. They carry along within their loops a colossal mass of living microorganisms. “Beyond Cape Town, they proceed on their journey, crossing the entire South Atlantic. We will continue to follow them and observe these beautiful rings on their transatlantic voyage. We locate them via satellite imagery, then we sample them. The question is: How do these circles, and the life they transport, cross the Atlantic? From a biological point of view our knowledge is still very limited in this field. Past expeditions have focused mainly on the physiochemical aspect of things (salinity, the size of these rings, etc). Passionate biologist, Chris is clearly proud to be rectifying this omission.

“The other area we want to study will take us to the shores of the Antarctic Peninsula. Multitudes of diatoms, which are phytoplankton (photosynthesis-performing organisms) live in these waters.  Diatoms proliferate in the glacial Arctic Ocean around the edge of the Antarctic continent.  They seem to like living around the poles.

Like their microscopic brothers and sisters comprising the phytoplankton, diatoms feed at the surface of the ocean on carbon present in the air. But when diatoms die, weighted by their tiny skeletons, they sink to the ocean floor, carrying the carbon with them. So they naturally trap all this carbon that we generate. Understanding how the diatoms live and adapt to changes in the Earth’s carbon dioxide level is therefore essential. The circumpolar current, the giant gyre surrounding Antarctica, thanks to all these diatoms, is the largest carbon sink in the world.

This is of particular interest to Chris.  To be thorough, he doesn’t forget to add that “our eight months around South America will also allow us to study, in the southern Chilean channels, the impact that fish farms in the area are having on plankton ecosystems.  And let’s not forget about our stopover in the Galapagos. In this part of the world the ocean is particularly acidic. Apart from the study of coral, we want to try and understand how plankton is adapting there. If this acidity were to become standard throughout the oceans, the Galapagos constitutes a living laboratory. Especially knowing as we do now, that life in the oceans is affected by climate change.

“But in addition, the Galapagos takes us back to Darwin, since that’s where he put together his famous theory of evolution.” Chris’s face lights up again, as before, when we were discussing diatoms.

The biologist takes a book from his library: The Voyage of HMS Challenger, in 1872, which took place well-after Darwin’s Beagle voyage. “We know that Darwin was investigating life on earth. Tara Oceans follows in the footsteps of this other British expedition, the first oceanographic expedition in the history of mankind. Way ahead of their time, the men aboard the Challenger were interested in sediments, and crossed the South Atlantic several times in pursuit of that interest. On board there was a certain Ernst Haeckel, naturalist, biologist, artist. Some of his drawings of plankton inspired an archway for the Universal Exhibition in Paris in 1900.” For a long moment Chris admires one of these drawings. Our voyage is also leading us on a journey into the past.

Though he’s not making drawings for Tara Oceans, Chris enjoys reviving the romance of these great expeditions. For him, it’s another of his goals of this new year: to convey the message that science, art and adventure on the seas are still closely connected, just as they were in the old days. 

Vincent Hilaire