10 February 2022
At the moment, the laboratory is working day and night: Rosette, Marine Snow Catcher, Plankton Net, Colonisers, Sediment Trap... The teams have been very efficient, albeit at the cost of their sleep.
We'd love to share everything with you in real time, but the connection at sea and the pace on board mean you'll need to be patient!
Marine Snow Catcher (MSC)
Marine snow fascinates... and as a result, the MSC doesn't get much rest! Neither do the teams... Sampling is carried out day and night at different depths to obtain as much data as possible on the particles.
Pauline practises these sampling protocols in the laboratory alongside Marc, Chloé, Sophie and Najib.
As a reminder, the MSC captures 100L of water in a desired area and then separates the particles according to their falling speed. After decantation, three parts are differentiated: suspended particles (which float), slow sinking particles (which sink gently) and fast sinking particles (which sink rapidly to the bottom). The speed at which the particles fall depends on their density.
The team is interested in the bacteria that live on marine snow. They would like to describe the bacterial communities associated with particles according to their speed of fall in order to gain a better understanding of the biological carbon pump that they represent.
Thanks to the MSC, they can take samples of the bacteria present on the particles of one stage of the water column (suspended, slow sinking, fast sinking).
So do these grigris work?
The team handles all three sections: hanging, slow sinking and fast sinking, applying the same method each time.
They pass the relevant quantity of water through a pump that gently diffuses the water through filters with different mesh sizes. The particles are filtered according to their size, which makes it possible to obtain a second sample. Marine snow particles populated with micro-ogranisms will be studied in the MIO lab in Marseille.
The researchers will attempt to identify the bacterial species present in the layers of particles using their genes. To do this, the bacteria will be lysed (broken up), and only their genetic material will be preserved. Once extracted, the nucleic acid (DNA, RNA) will be compared with the genes listed in a database that holds the genetic archives of micro-organisms that have already been studied.
Bacteria are defined, on the one hand, by genes common to the bacterial world and, on the other, by more specific genes common to a particular species of bacteria. Researchers will use the latter to identify them!
The luck that emanates from Chloé's grigris may lead them to discover bacterial species that have never been described before!
Sediment Trap
This strange tool is part of the panoply of our microbiologist oceanologists on board. It's a particle trap that, like the Marine Snow Catcher, samples particles in the water. Only, it doesn't sample an area of the water, but captures the marine snowflakes as they fall. The sediment trap is immersed to the desired depth and left for the desired number of hours. It retains the particles of marine snow as they descend inside these 4 tubes (photo).
Chloé has ingeniously developed a gel to trap the particles. She places a slice of it in each of the tubes before they are immersed, and the particles land on it naturally. Once they have penetrated the gel, they are captured! This gel has chemical properties that freeze any biological activity of the micro-organisms, so Chloé can recover the particles one by one and study them separately.
Unlike the studies that follow on from the Marine Snow Catcher, this one allows us to study the bacterial community present on each particle of marine snow sampled.
The Nautile still in action
The teams aboard the ship are not stopping, and neither are the Nautile teams underwater! The missions on the EMSO-LO site continue as long as the swell allows.
Some of the infrastructure still needs to be moved, connected or deployed. Launching the equipment is just the first step in putting it in place.
The Nautile's operations are long and meticulous, but so far they've been guided by success!