I seriously wonder what the local people think, when this suspicious group of young men passes by on its daily walk to work. Two sharp dressed Nigerians, one Italian constantly receiving phone calls and myself, who phenotypically would rather be expected in Scandinavia, than 100 kilometers offshore from Morocco. But I can assure you, we are neither on the run nor pursuing any shady business. We are “The Filtration Team”. Our mission is filtering water samples, a fundamentally important activity in oceanographic research. The measurements performed on the filtered samples allow insights into many different parameters of plankton ecology and biogeochemistry.
Our mission: filtration at its finest.
Every sampling day starts with the same routine of filling the canisters with water from the mesocosms, by using sampling tubes. Afterwards the samples are transported to PLOCAN and stored in a cooling chamber. In this freezing underworld, where jackets and scarfs are indispensable for survival, we fill our filtration bottles. Back in the lab, the samples are poured into the funnels of the filtration racks, which are connected to a pump, creating a vacuum.
Filtration in action
By using filters of different pore sizes and materials we are able to concentrate samples for various purposes and further analyses, for example for particulate organic carbon, nitrogen and phosphorus, biogenic silica, chlorophyll and fatty acids. Each of them represents a piece of the puzzle about what is going on with the plankton community in our mesocosms. The amount of biogenic silica for instance indicates how much diatom biomass there is, the most productive group of marine phytoplankton and one central focus of this project. In most filtrations we use chemically inert glass fiber and cellulose acetate filters.
Preparing the filtration rack for the next load of samples.
Although the work itself is not rocket science, it requires our full concentration, since routine and boredom lead to errors. Vessels and petri dishes for further storage need to be labelled carefully. Volumes for filtration need to be obtained precisely. Also we need to ensure that every single filter is placed properly on the rack without any contamination that could distort the measurements later on. Even the smallest dust particle floating through the laboratory could make the difference. Multiple racks need to be observed at the same time, while no filter should run dry. The used vacuum should not exceed 0,2 bar otherwise the probes could be damaged. Furthermore the storage of the probes in an oven or fridge has to follow a precise routine. Our holy book in the whole process is the “sampling protocol” in which filtering durations need to be noted as well as every small deviation from the norm. This is necessary to trace back sources of possible error later on.
After spending some hours in this almost meditative focus, you tend to forget about the world around you and just become one with your task. But caution, this mental flow is not without side effects. Reflecting back, I have to admit, that most of our conversations during this time were not necessarily of high intellectual value. Some might seem confusing or even insane to outsiders. Weird dancing, talking to the gods and the improper use of German words are just some incidents I want to mention here.
Finally I want to express my gratitude on behalf of the filtration team to all our supervisors for patiently instructing us, giving advice and for some pretty interesting conversations. Especially Andrea (L.), Silvan and Peter invested a lot of time and nerves into training us. And I guess not because they have nothing else to do.
David preparing the labels for the next day.