3 March 2012
Saturday March 3rd: We have only 650 miles to go before reaching the Azores. We’re sailing over depths of 5,000 meters, approaching the Atlantic ridge, the spinal column that characterizes the bottom center of the Atlantic Ocean.
With the different sampling stations done since Bermuda and those still to come before we arrive at Horta Island, our chief scientist Chris Bowler hopes to penetrate the mystery of life in this ocean – life largely influenced by the activity of underwater volcanoes running the entire length of this abyssal ridge.
There’s so much life at the bottom of the Atlantic Ocean, with hot springs and active volcanoes – probably at the origin of life on Earth – what types of organisms are found in the first 1,000 meters? Do they resemble those that emerged when the Atlantic was born, with the breakup of the Pangea and the beginning of volcanic activity?
Chris is passionately interested in answering these questions, but first we need to review some history. The Atlantic Ocean was born 450 million years ago, when the continents of America, Africa and Europe first appeared. It was named ‘Atlantic’ in 1507 right after the discovery of continental America by Amerigo Vespucci.
To understand Chris’quest, some basic notions of geology are necessary to perceive the dynamism of this ocean. In the beginning there was a single ocean, the Pan Thalassa. With the splitting apart of the Pangea – the planet’s original, unique land mass, the Atlantic Ocean emerged from the seismic activity that broke and pushed the land to both sides. In fact even today the underwater volcanoes continue a movement begun millions of years ago: geologists estimate that the Atlantic widens by 2 meters every 100 years.
The Atlantic ridge was discovered in 1850 by ships posing telegraph cables on the sea bottom between Europe and America. Men working aboard the cable-laying ships were the first to notice a significant rise in the sea bottom level. Before them, no one had any knowledge of this. But what about the life in this ocean?
Initially, the entire scientific community considered the Atlantic to be an ‘azoic’ region, without life. The Challenger expedition (1872-1876) was the first to explore the water above these depths, and discovered living organisms. Off the coast of Brazil, the Challenger explorers were surprised to find not far from the coast, water at zero degrees where organisms were not the same as in warm, tropical currents. This water coming from Antarctica runs northwards through the depths of the Atlantic Ocean. Indeed many ‘layers’ of water exist, as other scientists before Challenger had imagined, but the species living there move between the layers, so these are not separate, closed environments. Sometimes the layers even mix together.
But the mystery remains about organisms living above the Atlantic ridge volcanoes. Does life there resemble the original explosion? Let’s go back to those cable ships which brought up living organisms from the depths along with their pipes – giant worms, shells and sponges among other things. Closely studied a few years later thanks to CNRS submarines in collaboration with IFREMER, the worms revealed some extraordinary things.
After they were analyzed in special decompression chambers, the worms were found to have particular proteins allowing them to endure very different temperatures on each side of their body. So, very rich forms of life exist near these abyssal fumaroles, where there’s heat, but also sulfur, iron, and quantities of nutrients.
This ocean bottom is the matrix and cradle of pelagic life, and perhaps the origin of life 3.5 billion years ago. But do any ‘representatives’ exist closer to the surface?
This is what Chris wants to know and what inspires his research, and particularly this transatlantic voyage. “The instruments aboard Tara don’t go very deep, only to 1,000 meters, but that’s enough to know if the life forms we find could have developed in conditions similar to the origins, thanks to the presence of this volcanic matrix below. Studying these organisms some of which come up from the great depths at night, we can get information about earlier life forms.”
The interest of this leg, as we gradually approach the Azores located on the eastern part of the Atlantic volcanic chain, is this life in the deep. “After the first two sampling stations and before the next one, the 150th since the beginning of Tara Oceans, we can say that there’s very little life in the first 200 meters from the surface. But below that? »
Still another point that the expedition will no doubt clarify. Like borings taken in ice, exploring the layers of the oceans will perhaps bring us back to the origins. It took a long time to conquer Mount Everest on land. When will we conquer the underwater Everest?