03 February 2022
It's time for the first launch, and it's a moment as important as it is delicate. After a short night, the mobilised teams are on deck at 4:00 to send the BJS (from theIfremer) and the seismometer (from GeoAzur) at the bottom of the site.
The BJS is an essential component for the operation of equipment at the bottom. Its role is to provide an electric current and an Internet link to the devices located 2400m away: it is an intelligent multi-socket. It is submerged with its 200 metres of cable that can be seen wound on the gigantic spool. This cable will be needed to establish a link with the 'Node' connecting the KM3NeT Neutrino Telescope (LSPM) already in place, relaying energy to the bottom from the ground. The BJS cable will be connected to the 'Node' later in the mission using the Nautile submarine and its electronic arms. Tonight, the aim was to lower the BJS to the bottom - one step at a time.
The seismometer was also lowered during this first descent. It was placed at the EMSO-LO site, at the same depth as the other equipment, to monitor gravity instability and understand the behaviour of the seabed. The EMSO-LO site is indeed a multidisciplinary underwater observatory!
The BJS and the seismometer are well in place, 3m from their target at a depth of 2440m!
Photo credit: Nicolas Fromont - @nicolasfromontphoto
Plankton sampling
Plankton is a group of animals and plants, generally invisible to the naked eye, called zooplankton and phytoplankton respectively, which move with the currents. And this morning, it's plankton sampling time with the sunrise! Marthe is looking for bioluminescent micro-organisms.
The onboard technical team deploys its plankton net. This is the simplest tool for collecting small organisms. The water enters at the top of the cone and is filtered by guiding the particles towards the bottom of the net, called the collector. The net is submerged to a depth of 100m and raised at a slow speed (50cm/sec) to be as gentle as possible with the plankton.
Marthe will then sort her sample by identifying the different groups of species present. She will be particularly interested in those that emit light, and the bioluminescent organisms will be taken back to a team at the MIO for more precise identification. This will advance our knowledge of the bioluminescence of marine organisms!
Photo credit: Nicolas Fromont - @nicolasfromontphoto
In the lab, researchers are looking at a natural phenomenon with a rather poetic name: marine snow. This term is used to describe the organic debris formed in the upper layers of water and drifting slowly towards the seabed. This debris is said to be organic because it is mainly made up of dead animals and plants (mainly plankton) and faecal matter. This phenomenon of decomposition is comparable to leaves and other materials falling to the ground in a forest, except that it resembles a shower of flakes, hence the name "marine snow"!
It is a source of food for many species, from the largest to the smallest. But it is also an important oceanic process in the carbon cycle: At the surface, photosynthesis by phytoplankton (micro-algae) uses the carbon present in the atmosphere in the form of CO2 and transforms it into different carbon molecules using solar energy. This atmospheric carbon is therefore captured and continually carried down to the seabed by particles. This is how the carbon is stored in the sediments of the ocean floor. Marine snow that sinks to a depth of more than a kilometre stores carbon in the deep ocean for more than 1,000 years, preventing the carbon from returning to the atmosphere. We can therefore speak of carbon sequestration. This rain of particles is slow: some flakes can fall for weeks before reaching their destination! The largest particles sink the fastest, and the smallest do not necessarily reach the bottom. The longer they fall, the greater the chance that they will be digested by an organism or colonised by bacteria... And that's what the scientists on board are all about! They are interested in the bacteria present in marine snow.
Photo by Virginie Riou, CNRS - 2021.The Marine Snow Catcher
To find marine snow without having to dive, use a Marine Snow Catcher. It collects particles of marine snow with a minimum of trauma. It's a PVC structure in the shape of a bottle with a volume of 100 litres, only it has two openings: one at the top and one at the bottom. Its operation is simple: it is immersed in the open position at the desired depth (Marc and Chloé sent it to 100m) then, once full, it is closed again on command from the shore. The Marine Snow Catcher thus captures the desired column of water and raises it gently. After recovery, the device remains upright on deck for 2 hours to allow the particles of marine snow to sink to the bottom. This is the settling phase. Then, very carefully, the first 95 litres that contain no particles of interest are drained off through a tap. The lower part of the water bottle contains the remaining 5 litres of water and the sea snow. This is the part that is recovered for the laboratory!
In the photo, Najib and Marc retrieve the Marine Snow Catcher from the crane and leave it to settle.
Photo Credit: Nicolas Fromont - @nicolasfromontphoto
This is the second boat launch of the day! The radiometer on the CPPM left for the underwater observatory this morning and is the first radiometer to be sent to this depth in the Mediterranean!
But what exactly is a radiometer? It's a tool used to measure the radioactivity of an environment. Radioactivity is a ubiquitous natural phenomenon. It is caused by atoms seeking stability: when atoms have excess energy, they disintegrate by ejecting some of their neutrons and protons to find a more stable form. All this generates radiation, which is known as radioactivity. (Radioactivity can also be artificial, as in the case of nuclear power stations).
This radiometer has been designed to be stable on a tripod, and its radioactivity detector faces downwards to protect it from falling particles. If it is covered, it will no longer be able to take measurements! The long tube above the detector is the probe, which collects and processes the information received by the detector. Higher up is the radiometer's electronic container. The whole thing is protected by a cover, the disc at the top of the infrastructure. The radiometer is one of the devices connected to the Scientific Junction Box.
Thanks to this radiometer, researchers at the CPPM will be able to follow the measurements of radioactivity in the depths - radioactivity that is still little known!
Photo credit: Nicolas Fromont - @nicolasfromontphoto
The BathyBot launch
It's BathyBot's turn to join the EMSO-LO site at a depth of 2,500 metres! This robot was designed by Christian Tamburini and Séverine Martini, and its technical aspects were carefully developed by Carl Gojak and his team (INSU, MIO, OSU – CNRS).
BathyBot is a benthic robot, in other words a robot designed to explore the seabed. Its mission is to study bioluminescence in a quite unprecedented way, using a hypersensitive camera. BathyBot is equipped with cameras and sensors that will enable it to observe biodiversity and study the flow of particles. In this way, researchers hope to understand the biogeochemical dynamics of the deep environment (biogeochemistry is concerned with the transformation of organic matter, and major elements such as carbon, under the effect of biological, geological and chemical processes: Bio-Geo-Chemistry).
BathyBot is launched in its BathyDock, a rallying point on which you can clearly see two coiled cables, one red and one blue. To operate, the BathyDock will be plugged into the Scientific Junction Box (the smart power strip at the back) using the red cable. The blue cable will act as a leash for BathyBot: it will be able to walk around the BathyDock while attached to its structure - while receiving electricity and internet for image transmission. The orange rectangles are floats that allow the cable to float. They are ingeniously designed to allow the leash to form a floating arc when deployed, preventing BathyBot from getting tangled up!
The Nautile submarine will soon be heading to the bottom of the site to check that BathyBot has arrived!
Photo Credit: Nicolas Fromont - @nicolasfromontphoto