6 May 2013
Interview with Marc Picheral and Céline Dimier, scientific engineers.
Based at the Laboratory of Oceanography, Villefranche-sur-Mer, Marc Picheral coordinates the installation of some scientific equipment aboard Tara, including everything for the “Dry Lab”. Engineer at the Roscoff Biological Station, Céline Dimier is managing the equipment destined for the “Wet Lab”. We asked them about the material that will accompany the boat for the “Tara Oceans Polar Circle” expedition.
Besides the equipment already present during the Tara Oceans expedition, what will be added ?
Marc Picheral: For the equipment on deck, we’ve modified the Rosette – an instrument that collects underwater samples and measures oceanographic data. We’ve added an underwater sensor that measures illumination, important for photosynthesis. We’ve also added an acoustic sensor (AQUAscat) that can count in a volume slightly larger than optical systems, small objects such as plankton or certain particles suspended in water.
Céline Dimier: In the Wet Lab, the material is basically the same and consists mainly of pumps of different sizes and types (air pump, water, peristaltic, etc.) and filtration units of all kinds (25 mm, 47 mm, 142 mm, tripods, ramp filtering, etc.). With Steffi Kandels-Lewis (logistics engineer) we also calculated, based on the sampling plan, the numbers of tubes, flasks, filters, and boxes needed for a 6-month assignment. And then we also calculated the volume required to store the samples according to their required temperature: RT (room temperature), 4°C (refrigerator), -20°C (freezer), -196°C (liquid nitrogen). All this equipment is used to collect and store the samples of bacteria, viruses and protists destined for genomic analysis or microscopy.
Will other instruments be added to this list ?
Marc Picheral: We’ll be using a continuous plankton recorder from Murmansk to St-Pierre-et-Miquelon. This instrument has been in use for decades, mainly in the North Atlantic. It is towed by merchant ships and continuously collects plankton on rolls of silk.
In addition to this, our surface optical sensor used to characterize solar irradiance during stations, will be replaced by the C-OPS (Compact-Optical Profiling System), a similar sensor, but which can take profiles down to 100 -150 meters. We’ll be able to characterize illumination on the descent and ascent.
Will you also make some additions to the Dry Lab ?
Marc Picheral: Yes, we’ll be adding more light sensors, connected to instruments in the Dry Lab and the forward hold, that will function 24h per day.
There will be one continuous CDOM (Colored Dissolved Organic Material) sensor, and another (Ultrapath) which determines more precise CDOM levels in samples taken with the Rosette bottles at depth.
We’ll have new sensors placed in the forward hold, but controlled from the Dry Lab, i.e. the ALFA (Aquatic Laser Fluorescence Analyser) optical sensor, and the FlowCytoBot, an imaging sensor for identifying microorganisms. In addition there will be the SeaFet, a pH sensor, because of sea water varies according to the CO2 content.
How will you protect the equipment from the cold ?
Céline Dimier: We have to adapt the boat for polar conditions. We’ll provide heating for the Wet Lab and insulate pipes to prevent freezing. We’ll also test the containers for cold resistance (this depends on the type of plastic used). The water purifier will be equipped with water cartridges that function with very cold water (5°C). We’ll also ensure that the reagent solutions can withstand low temperatures.
Marc Picheral: Some sensors resist the cold, while others can not tolerate freezing. We’ll therefore use tarpaulins, electric blankets and hot water systems to protect our sensors when they’re out of the water.
But for equipment maintained inside the boat, the problem is not the cold but condensation. Surface water in the Arctic can be -2°C, and then it passes through our instruments at 20°C. This causes condensation, which will prevent optical imaging. Some instruments will have to be set up in the forward hold, though we’d prefer to put them elsewhere in the boat. This is a question still to be resolved.
Interview by Anne Recoules