Day 6 - Let the samples shine !
5th february 2022
It's all about the rosette
The scientists on board are interested in seawater microbiology, and the rosette sampler is one of the most important instruments on board.
This measuring device is used to sample different layers of water with 12 bottles arranged in a circle. The sampling is accompanied by the measurement of temperature, depth and conductivity. Conductivity measures the ease of moving of the electrical charges, and here it's in salty sea water. The saltier the water is, the better the conductivity is. We can therefore make the following shortcut: the measurement of conductivity is an indicator of salinity.
The water catcher works like the Marine Snow Catcher (described on Day 4) : the bottles are dropped in water in an open position and are closed at the desired depth. Having multiple bottles allows the collection of samples at different depths, in a way to compare data.
This rosette sample includes additional measuring tools:
- a fluorometer: it indicates the amount of phytoplankton biomass by measuring the chlorophyll present in the micro-algae
- a granulometer: it measures and classifies the particles in the water thanks to a laser measurement, it's a tool borrowed from geologists and applied to oceanology
- an Underwater Video Profiler : it allows to give specific measurements of plankton particles thanks to images taken by a camera
- a transmissiometer: it measures the content of particles that disturb the water, called turbidity
With all these parameters, we can only be satisfied !
Crédit photo : Nicolas Fromont - @nicolasfromontphoto
Rosette in the morning, Rosette in the evening
Dominique, Marc, Christian, Chloé, Pauline, Najib and Sophie are all involved in the rosette missions.
They try to study the nycthemeral migration of plankton. This word of Greek origin means "a night and a day", so a nycthemeral migration is a migration that occurs according to the day and the night. To study this phenomenon, they have to immerse the rosette twice a day at 600m, once very early in the morning and once in the evening. And to make their studies meaningful, it's necessary to base them on a maximum of data, which implies repeating this choreography every day. It's a demanding work rhythm, but when you love, you don't count!
All these manipulations have attracted little fairies on board !
Crédit photo : Nicolas Fromont - @nicolasfromontphoto
More like fairy bacteria...
This is it! Bacteria responsible for bioluminescence in the depths have been cultivated in this petri dish! Each point is a colony, a real bacterial microcity!
These bacteria will soon be isolated, which means in laboratory language that they will be separated and grown in different dishes. The researchers will then be able to bring them back to Marseille to identify them.
Crédit photo : Nicolas Fromont - @nicolasfromontphoto