Day 11
10 february 2022
Lately, the laboratory has been running day and night: Rosette, Marine Snow Catcher, Plankton Net, Colonizers, Sediment Trap... The teams have been very efficient, even if at the cost of their sleep.
We would like to share everything with you in real time, but the connection and the work rate on board require a little patience!
Marine Snow Catcher (MSC)
The marine snow fascinates... and the MSC doesn't know much rest! Neither do the teams... Sampling is done day and night at different depths to get a maximum of data on the particles.
Pauline is practicing in the laboratory through sampling protocols with Marc, Chloe, Sophie and Najib.
As a reminder, the MSC allows to capture 100L of water in a desired area and then separates the particles according to their falling speed. After decantation, three parts are differentiated: suspended (which float), slow sinking (which sink slowly) and fast sinking (which sink fastly to the bottom). The falling speed of the particles 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 the particles according to their falling speed to better understand the biological carbon pump they represent.
With the MSC, they can sample the bacteria present on the particles of a water column stage (suspended, slow sinking, fast sinking).
So does these lucky charms work?
The team takes care of the three parts: suspended, slow sinking and fast sinking; applying the same method each time.
They pass the relevant amount 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 allows to obtain a second sampling. The marine snow particles populated with micro-ogranisms will be studied at the MIO lab in Marseille.
The researchers will try to identify the bacterial species present in the particle layers using their genes. For this, the bacteria will be lysed (broken), and only their genetic material will be preserved. Once extracted, the nucleic acid (DNA, RNA) will be compared to the genes listed in a database that keeps the genetic archives of microorganisms already studied.
Bacteria are defined on the one hand by genes common to the bacterial world and on the other hand by more specific genes, common to a bacterial species. Researchers will use the latter marker to identify them!
The luck that emanates from Chloe's lucky charms may lead them to discover bacterial species that had never been described before !
The Sediment Trap
This strange tool is part of the toolbox of our oceanologists on board. It's a particle trap that, like the Marine Snow Catcher, allows to sample particles in the water. Only, it does not sample an area of the water, but it 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 fall 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 enter the gel, they are captured! This gel has chemical properties that freeze any biological activity of the microorganisms, so Chloe can retrieve the particles one by one and study them separately.
Unlike the studies that follow the Marine Snow Catcher, this one allows the study of the bacterial community present on each particle of marine snow.
Le Nautile still in action
The teams aboard the ship don't stop working, and neither do the teams on the Nautile underwater! Missions on the EMSO-LO site continue as long as the wind allows it.
Some bottom infrastructures still need to be moved, connected or deployed. The launching of the devices is only the first step in their installation.
The Nautile's operations are long and meticulous, but so far guided by success!