Life around the rosette by Ribanna

As CTD watchstanders our duties are deploying and recovering the CTD rosette at every cast safely and to make sure we collect water at the prescribed depths. The CTD rosette contains multiple sensors measuring different parameters while the instrument travels through the water column - such as temperature, salinity, pressure, oxygen, fluorescence and more. The rosette is surrounded by 36 so-called niskin bottles which can be “fired” separately at the desired depth so that eventually we will have water samples from throughout the water column. 

The CTD rosette out of the water, after the cast (ph by Timoor)

While we go through several cycles of excitement in each cast (does the winch unroll correctly? Is the bottom depth right? Can I fire the bottle now or do I have to wait another 4 seconds? Did we estimate the time of the rosette back on board correctly?), the real thrill kicks in when the rosette comes back out of the water. While the marine technician secures it safely in the Baltic room, herds of enthusiastic samplers are waiting in front of the Baltic room door. But they are not allowed to start sampling without the sample cop. The sampling cop is in charge of keeping everything under control while the samplers go wild around the rosette. Samples for gasses, such as CFC and oxygen, have to be sampled first as with the moment the vents are opened, atmospheric gasses can easily contaminate the water. Everyone needs to stick to the order. Everyone wants their samples as quickly as possible. Everyone has up to 36 samples to take. In principal, the sampling procedure is almost the same for all of them with slight differences. For example, I am either sampling for alkalinity or for radiocarbon. While both require thorough rinses of the sample bottle, the stopper and the tube, alkalinity is definitely the easier one. Radiocarbon sampling turns out to be prone to contamination so that the moment I put on my lab gloves, I am not allowed to touch anything but the sample bottle and the sampling tube. And the sample bottle or tube are not allowed to touch anything either! That’s how paranoia start!

Sampling around the rosette, in the Baltic room

The Baltic room is quickly filled with the shouting of numbers forth and back between all the samplers and the sample cop until the very last person is done sampling. For all parameters to be sampled it can easily take up to two hours. However, over the last few weeks we all got used to our tasks onboard the ship so that we have been able to make the whole process of sampling a lot faster already.

Ribanna, dayshift CTD watchstander