by Michelle Albinus, Claudia Thölen and Jochen Wollschläger
7:05 a.m. My first walk takes me not directly to breakfast (and to the loudly calling coffee), but to the universal lab – my cave, my playground. In the center is a large, square wooden table with laptops and protocols spread out on it. Along the walls are lab tables that house all of our equipment. During the course of the sampling station three of them will reveal to me what particles are in the water by absorbing light.
First, though, I’ll see if my ADCPs (Acoustic Doppler Current Profiler) are doing well. The two current sensors are installed in the moonpool and the side of the RV Meteor and provide continuous data that is displayed on the lab’s monitor. Check. Just a handle away, the Shimadzu (called René), a dual-beam photometer, is waiting to be turned on, as is the LS55, a fluorometer called Sofia. Both will later receive 0.2 µm filtered sample water in clear glass cuvettes to determine the concentration of Colored Dissolved Organic Matter (CDOM) in the case of René and Fluorescent Dissolved Organic Matter (FDOM) in the case of Sofia. I also prepare the tables in which I note information about the origin of the sample, the parameters of the measurement method, and the resulting data tables during the measurements. Check. Once turned 90°, two steps forward and I am standing in front of the PSICAM, an instrument that also measures absorption, but in the diffuse cavity of a cube illuminated by a lamp. This also has to warm up and the measurement environment has to be set up in the associated software. Check. 7:15 am. Off to breakfast!
Equipped with a second coffee, I return to my sanctuary, where my measurement-minded friends are waiting for me, ready for action. My colleagues also gather here first thing every morning: Jochen, Claudia, Kai and Neeske. The last two, however, usually disappear straight back outside. Sofia and René now need measurements with pure water in order to subsequently subtract the absorption from the sample data, which comes from the water alone and not from the particles they are looking for. Because René wants to have three of them directly, Claudia helps me so that I can devote myself to other things. The construction of the filtration unit, for example. Here a pump sucks the water through 20, 2 and 0.2 micrometer filters, so that I can also examine different size classes of material. I set up the filter and the announcement “On station” comes.
From the water bottles of the CTD I soon get my sample water from 100 m depth and the chlorophyll maximum (currently mostly 10 m). But I get the surface water from the tap. Yes really. The ship transports the water from 4 m depth with a pump to the labs, where I can pick it up and already start measuring this sample, while the CTD is not even back on deck yet.
Now it’s time to filter! The ubiquitous rattling of the pump mixes with the music, by which everyone can tell who is working here. While the water runs through the filters, I measure the unfiltered sample in the PSICAM – water into the cube, fiber optic cable and lamp in, measure the temperature (and don’t forget to write it down!), tap out the air bubbles, put the plug on and give the system the measuring command. Then pour the water back into the bottle, shake out the cube, wash with pure water and send the sample through the next filter. Now do this four times per sample for a total of eight different filtrates. Meanwhile, I fill the cuvettes for Sofia and René, wipe them carefully dry and clean with a cloth, and start the measurements (René takes about 15 min, Sofia takes 45 min). Back to the PSICAM and fill, tap, measure. A beep announces that René is done and wants to be fed, Sofia is happily whirring away. Around 10 a.m., I actually leave my lab briefly for once and descend deeper into the ship to take the daily salt sample (this will later be used to calibrate the thermosalinograph, a sensor that measures surface water parameters). The last drops fall into the bottles and one after the other Claudia, Neeske, Kai and Jochen return. The station draws to a close and I pour water from A to B for the last time. I turn everything off, clean my workplace and say goodbye to the PSICAM, Sofia and René. But only until the next station in the afternoon …