07 February 2022
Bacterial colonisers
Iron is essential to life and occurs naturally in the environment. Céline is interested in its oxidation by bacteria in the depths of the ocean.
Iron oxidation is a natural reaction that provides the bacteria with energy. It works as follows: oxygen atoms extract electrons from iron atoms, generating energy. It's the same principle as in a battery: the flow of electrons produces electricity, and that's how these so-called ferroxidising bacteria work.
The oxidation of iron transforms it into another type of iron, the process of rust formation, and the same thing happens in the bottoms.
The photo shows the colonisers prepared by Céline for bacteria living at 2400m. Each tube is a little living environment made to measure for them! Some contain plastic of different compositions, others iron of different origins.
Colleagues of hers would like to understand the degradation of plastics by micro-organisms and seawater at the bottom. They will also identify the species responsible.
Céline studies iron, and has chosen to use two different types. One of synthetic origin: iron shot (steel); and the other of natural origin: basalt glass. Basalt is a magmatic rock. During an underwater volcanic eruption, the magma undergoes extremely rapid cooling, which transforms it into glass, so it is called basaltic glass. It is glass, but very rich in iron. Here, it has simply been made in the laboratory to reproduce the basaltic glass produced by volcanic activity on the seabed. The colonisers will make it possible to study the oxidation activity of these two types of iron by bacteria.
We can study bacteria using iron, and we can go the other way by studying iron using bacteria! Depending on the ferroxidising bacteria identified in the seabed, researchers can determine the associated type of iron and monitor its evolution in the oceans. These studies are also aimed at understanding the impact of global warming on micro-organisms on the ocean floor.
Are you coming down?
The weather forecast predicts a return to calm tomorrow! The Nautile should therefore be ready to dive at 9.00 am! It will be sent to the bottom with a scientist and two pilots to check and adjust the positions of the equipment at the bottom.
In the meantime, we'd like to take you on a tour of this submarine, designed for exploration and intervention at depths of up to 6,000 metres. As a reminder, the living area is a 2m² sphere fitted with a rebreather system that maintains a normal oxygen level and eliminates the carbon dioxide released. The air passes through granules of soda lime, which remove the carbon dioxide. This is known as a re-breathing or circular circuit.
The entrance is on top of the Nautile, and to get there you have to climb to the top floor of the hangar. Here's the hole you have to crawl through to get down!
In the Nautile
Here we are in the living area. It's a bit cramped, but you quickly feel at home! There are 3 small windows for the 3 passengers (pilot, co-pilot and scientist). Their small size is the result of a compromise between the thickness of the glass and the size of the observation window. Withstanding the pressure of 6,000 metres of water is equivalent to 600 kg of force per cm², so the glass must be solid! A larger window would require much thicker glass.
On the sides, the sphere is lined with buttons, electronics and equipment. So it's best to watch your movements and keep your position. The two cushions on either side allow passengers to lie down facing the window and watch the scenery when manoeuvring permits! Pretty cool, isn't it?
Guillaume is one of the co-pilots and is also the Nautile's electronics technician. During the dives, he is in charge of the Nautile's atmospheric management, the positioning of the craft, contact with the surface and taking images. For safety reasons, the Nautile must communicate with the surface every 30 minutes.
Also at the helm of Le Nautile are Olivier, co-pilot, Julien, pilot and technical manager, and Frank, pilot and head of operations. They take it in turns to ensure the Nautile's many dives. Rest and concentration are paramount.
Submerging, steering and recovering Le Nautile involves navigators, mechanics and divers. We'll show you their involvement in the diving of tomorrow!
Photo credit: Nicolas Fromont - @nicolasfromontphoto
Sailor and jeweller
Working on a ship requires rigour, organisation and coordination. It's also a manual job. For Aurore, who is a sailor, the manual side is also very creative! She makes jewellery from marine objects and mechanical materials. Tonight, she's offering us some original souvenirs!