DIADOM's kick-off

Hi all,

This is the first entry of the DIADOM project blog. The DIADOM ("Interactions between diazotrophs and dissolved organic matter in the ocean") is a postdoctoral research project funded by the Marie Curie Intra-European Fellowships, leaded by Sophie Bonnet and Mar Benavides.

In this project we aim to study diazotrophic nitrogen fixation (or N2 fixation) in the Southwest Pacific, focusing on heterotrophic diazotrophs and their relationships with dissolved organic matter. But... what does this all mean??? Let's see :)

N2 fixation is the process by which atmospheric nitrogen (dinitrogen or N2) is assimilated by microorganisms and transformed into a more bioavailable form of nitrogen: ammonium. The microorganisms called diazotrophs (from the greek di= 2, azo = nitrogen, trophos = nutrition) are the only ones capable of fixing N2, an incredibly tough task which takes a lot of energy.

And why should we care? Well, most of the global ocean surface is poor in nitrogen (the "fuel" phytoplankton use to take up atmospheric CO2), and diazotrophs are capable of bringing this nitrogen from the air into the ocean, boosting primary production and CO2 drawdawn (thus saving us from global warming and allowing the production of 50% of the oxygen we breath)... it really looks like something to care about doesn´t it?

After more than two decades of oceanic N2 fixation studies focusing on the sunlit layer of the ocean (first 100-200 m), now there is some evidence that diazotrophs could be also living in the deeper and mostly unknown dark ocean. The diazotrophs that inhabit these deep waters are inherently different from those living in the sunlit layer of the ocean: the first use organic matter as their nutritious source, while the latter rely on the light provided by the sun and CO2 fixed by photosynthesis.

Our goal is to investigate whether deep ocean diazotrophs use organic matter for their nutrition: which kind of organic matter they use? do different species of diazotrophs use different kinds of organic matter? Overall, we will gain new knowledge on the distribution of poorly studied diazotrophs in the depths of the ocean.

This project will benefit from oceanographic cruises in the Southwest Pacific. One has already finished, check out the MoorSPICE cruise blog here.
This cruise took place in the Solomon Sea between 28th February and 31st March 2014.

 The MoorSPICE science party onboard the R/V Thomas G. Thompson

  The R/V Thomas G. Thompson docked in Nouméa's harbour.


In July 2014 I will spend a whole month in the Mediterranean Institute of Oceanography (MIO) in Marseille analyzing the samples collected during the cruise. Preliminary results and impressions will be posted, follow us!

Cheers

Mar