30 November 2013
Since sampling station number 211 in the Labrador Sea, the rosette and nets have remained neatly stored on the rear deck. Does this mean no more scientific work will be done aboard Tara during the rest of the voyage, before our arrival in Lorient ? Explanation below:
The reason for ceasing the sampling stations is simple: a year and a half ago, the previous Tara Oceans expedition ended with a transatlantic crossing similar to this one, just a little further south. So there’s no reason to collect more samples in an area that we’ve already explored. But this doesn’t mean no science is being done aboard,” explained Fabien, oceanographic engineer. We’re still doing surface sampling — a whole range of sensors are constantly taking measurements on board.”
Specifically, a pump located under the hull of Tara collects seawater which is then analyzed by a multitude of sensors that measure the levels of CO2, quantity of suspended solids, pH, temperature, and salinity. Every day, the CNRS engineer sends a portion of this data to the international Coriolis program which collects all the physico-chemical data of water bodies sent by research vessels worldwide.
The continuous surface data is also automatically saved on several hard drives on board, to be sure that none of this valuable information is lost. “Every hour, I check the computers and instruments to make sure everything is functioning correctly,” says Fabien. At night, the people on watch do the same thing. It’s also the occasion to check the refrigerators where all the plankton samples have been stored since the beginning of the Arctic expedition – a very precious bounty.
Finally, Fabien takes 3 samples each day from water pumped beneath the hull: a milliliter of water is immediately stored in liquid nitrogen, 2 liters are filtered to collect plankton and other particles, and 100 milliliters feed the FlowCam. This device continuously photographs the water flowing through it and counts all the particles in suspension. The FlowCam can then classify them by size, and get a set of statistics. Thus, even without sampling stations, Tara continues adding to the huge data base accumulated during the nearly 7-month expedition.