Break-down of the nutrient amendment experiment

This day marked the end of my major experiment for the long duration stations (LD). After a 36 hour acclimatization, spiking with 15N2 and 13C -bicarb and then incubating for 24 hours it was finally time to filter the bottles with the different treatments.

For my thesis I'm collecting filters for SIMS (secondary ion mass spectrophotometry) analysis. So I want to see if the activity of the nitrogen fixation and growth for the DDAs (diatom - diazotroph association) changes when exposed to non-limiting conditions of certain nutrients.
In my case these nutrients only included iron, DIP (dissolved inorganic phosphorous) and DOP (dissolved organic phosphorous). Of course I also had a control bottle. My ambition was to also include treatments of silicate and vitamin B12, unfortunately there was a last minute change in the availability of these nutrients, so I had to settle with the ones I ran during this LD and a very limited amount of silicate which I will save for an LD where the DDAs are more abundant.

In addition to these SIMS filters I also filtered water for the diazotroph team responsible for measuring the bulk nitrogen fixation which I will use for later comparison. They wanted to specifically preserve filters for DNA and RNA which I will bring back to Sweden after the cruise. Since filtering water for DNA and RNA samples is somewhat my speciality by now, I was happy to assist.
This proved to be a bigger challenge than I had initially thought. There was a lot of multi-tasking involved since the filtration had to be set up for the different bottles and the water for DNA and RNA had to be split up and measured. The different filtrate purposes also required their own special filters and tubes with either a storage medium or nothing, and finally flash freezing in liquid nitrogen or just put in the -20 degrees celsius freezer.
While managing all this, the filtration time for the bottles varied a bit and I had to constantly keep an eye on the bottles and the time taken for each filtration and then get to work on storing the filters in the correct tubes (pre-numbered).
Rockstar filtration! I just missed some metal music in the lab!

All in all it was, as far as I can tell right now at least, a successful experiment. I just hope that I will actually find some DDAs on my filters when it's time to run the SIMS. My hypothesis is that iron will be the biggest stimulant since nitrogen fixation, specifically the nitrogenase complex, requires a lot of iron for its expression. This only takes the symbionts into consideration however. The diatom might need something in addition to iron (which is mainly used in the RUBISCO pigment for carbon fixation) for boosted growth, silicate perhaps.

After this hectic start of the day I treated myself with some quality time on front deck in the hot tropical sun listening to that metal music that I missed in the lab earlier today. The ocean certainly eminates a contagious calmness. I probably watched the gentle waves roll by towards the endless horizon for hours before hitting the gym.

Finally, I have now passed 500 unique views of my blog since I started some 2-3 weeks ago. I'm thrilled about the relatively large interest in my cruise, which far exceeds any expectations I might have had. Thank you all, it is very flattering. In return I give you this picture proving that nature indeed has a sense of humour.