Scientific goals and purpose

I suppose it is about time that I explain a bit about why I'm actually away on a scientific cruise (in more detail), what my goals are, what my responsibility on board is and what my field of expertise is exactly.

The fact that I just started my PhD at Stockholm University is probably old news for most people reading this, but field and scope of my thesis is probably not common knowledge (not even for my family, sorry guys), which might be the case for various reasons.
Anyway, my field is nitrogen fixation and nitrogen fixers in tropical open oceans, where my scope is on symbiotic relationships between phytoplankton (the diatom group) and nitrogen fixing cyanobacteria (also called diazotrophs). These symbiotic relationships, also referred to as Diatom-Diazotroph Association (DDA) are hypothezised to be very important for e.g. nutrient cycles in the open ocean and are quite understudied. Therefore I'm also interested in how these relationships play out in future open oceans in the face of global change.

I will try to answer the questions of activity and distribution of these DDAs as well as describing the very nature of the relationship and finally investigating the effects of global change (ocean acidification and global warming).

So the reason why I'm on this cruise is to collect samples for my thesis questions and research goals. I will do this by continuously take DNA samples from every station (in a depth profile) not knowing if the DDAs are present or not and then hopefully be able to take RNA samples (in a depth profile) when they are abundant. That might seem like enough work, but happily it doesn't end there. In addition I will be running experiments on board.
I will collect surface samples and spike with 15N2 and 13C, and then treat them with different substances and nutrients to find out what is limiting the DDAs and how. I will do this analysis by the use of the SIMS (Secondary Ion Mass Spectrometry).
I will also spike samples from a depth profile, again for analysis by the SIMS (with this instrument we can for example study the flows of N and C within single cells).

However, I've been out at sea for a few days now and not run any of the on board experiments yet, so most of the work I've been doing so far (except for my DNA samples) concerns my responsibility on board.
Putting together a cruise like this requires a lot of planning and work and there's the basic need for choosing sampling sites. So by the use of our qPCR I can target four different unicellular diazotrophs (UCYNA1, UCYNA2, UCYNB and UCYNC, too small to detect otherwise) and within a few hours after sampling provide a fairly accurate number of cells/liter in a depth profile (now when the standard curves of the qPCR are finally awesome).
The organisers of the cruise will use this data, together with some physical factors to decide where we put our long duration stations (LD).
It is very exciting that my data is that important but there is also the weight of responsibility, even heavier in this case, but if I were to chose again I would not have it any other way.