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IODA6000, the ANTARES' jedi spiritProduction and remineralisation of organic matter by microorganisms along water column is a key point of carbon cycle. If the euphotic zone has been much studied by all scientific community, activities in deep water are still not well known. One of reasons is the lack of techniques. Since last decades, new instruments have been developed (Bianchi 1999) to sample and incubate under in situ conditions (i.e. temperature and hydrostatic pressure). A method for quantifying remineralisation rates of organic matter is to measure the respiration rate of microorganisms but until now, there is no direct method to reach it. This is why a new tool has been developed through a tight collaboration between the LMGEM (Laboratoire de Microbiologie Géochimie et Ecologie Marine) and the CPPM (Centre de Physique des Particules de Marseille). The In situ Oxygen Dynamics Auto-sampler (IODA6000) is an autonomous and programmable equipment made of a 5 litre incubation chamber auto sampling water at its depth of immersion. At high frequency, temperature and oxygen concentration are measured in and out the chamber by two optodes Aanderaaô. The combination of these measured parameters enables to derive the respiration rates in the dark ocean and to observe the evolution of water masses oxygen contents. |
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Bientôt, en français. | ||||||
DataIODA6000ôs data on ANTARES site at 2000 m depth from May 2008 to September 2010 are presented on the figure on the right. Each cycle is 5 days long, with an opening time of 3 hours in order to remove completely the water sample.
Since 2008, in situ oxygen concentration fluctuates a lot with a delta of 2 to 3 ôM, even at short time scale. This first result is surprising compared to discrete measurements by CTD profiles. In parallel, mean respiration rates measured in the incubation chamber is around 0.3 ôM O2 d-1. This result is 2 order of magnitude higher than predicted by indirect measurements (Del Giorgio and Williams 2004). So this is another surprising result, but concomitant with previous study (Tamburini 2002) which has shown that activities of samples incubated under in situ conditions are higher than those incubated under atmospheric pressure. Contact persons: D. Lefèvre & C. Tamburini (dominique.lefevre@univmed.fr;ô tamburini@univmed.fr) |
Oxygen concentration
measured by the IODA6000 on
the
ANTARES site from May 31th 2008
to September 2010. |
Author : Thierry Stolarczyk