Carbon,Nitrogen & Oxygen Fluxes associated with the cyanobacteria Nodularia spumigena in the Baltic Sea:
All nutrients are a necessity to growth and survival at any trophic level and carbon, nitrogen and oxygen are most probably the key 3. The demand and competition for them in the oceans is massive and so their are numerous sources and studies happening to test just how good an organism is at retrieving and utilising these things.
A study by Ploug et al. (2011) looked at the fluctuations in these chemical concentrations in the day and at night. To test whether there was a fluctuation and if so was it significant. To test this the study looked at Photosynthesis, Nitrogen Fixation, Respiration & Ammonium release during an algal bloom in the Baltic Sea in August 2009.
The way they tested each parameter was to: for photosynthesis and respiration they transferred freshly sampled colonies to a petri dish coated by a 3mm thick agar layer which was then covered with water from the sampling site. Diffusion on this agar is similar to that in the ocean so the test is accurate for gas diffusion. The petri dish was then transferred to to a thermostated container at an in situ temperature. From here the oxygen concentration gradients were measured using a clark-type oxygen microsensor.
For the Carbon analysis, the samples were injected into an acid stream (30mM HCL) to convert dissolved organic carbon into carbon dioxide. These samples were then analysed in a flow injection system coupled to a conductivity cell.
Finally for the ammonium analysis, these values were quantified in the filtrate after incubations with nitrogen during 0,3 & 6 hours in light or darkness using a method originally used by Warembourg 1993. Then from this the samples were analysed on a gas chromatography isotope ratio monitoring mass spectrometer.
The results from all of the above analyses showed that at the beginning of the bloom the dissolved inorganic carbon decreased significantly and that the carbon and nitrogen fixation rates in the day were larger by a ten fold increase than those rates in darkness. Within the bulk planktonic community the average ammonium release was six fold higher in light than in darkness. It was noted that although the general trend about carbon and nitrogen fixation was seen the exact fixation rates were highly variabl between individual cells.
Also as with the studies looking at how iron induces extra growth of cyanobacteria it is useful to see that in the light environments this cyanobacteria thrives, so should there need to be a mass collection of this species it could be concluded that a bloom is the best location etc.
This study is interesting and useful for the future as not only does it add to the information that is known about fixation rates for this specific species but it also adds a replicable method for other studies should there be any.
The url of this paper is below:
http://www.nature.com/ismej/journal/v5/n9/full/ismej201120a.html
Any questions please let me know.
Hi Oliver,
ReplyDeleteI was just wondering whether the people mentioned anything about why the ammonium release was higher in light conditions?
Thanks,
Sophie
Hi Oliver,
ReplyDeleteIs this paper just a species specific contribution to the literature, reporting specific rates of usage? It seems to me rather obvious that fixation rates for phototrophic cyanobacteria would be quicker in the light when photosynthesis and light-dependant carbon fixation is going on... or have I missed the point entirely here?
You make a good point about the method here, it is nice when papers actually describe their method in such a way that you could repeat it and be convinced of its reliability and validity, or not as the case may be.
hey vicky, i was always of the assumption that it was a start of more research sort of thing, so it is species specific but will spark other comparisons and build up a sort of library of results, yes it is pretty obvious that the results were expected, and it doesnt say they used them with any other data sets from other experiments so yes im with you on that front.
ReplyDeleteYes all it says is a similar method to Warembourg 1993, and i checked online and you can find this method, all you have to do is google it :)
Let me know if theres anything else i can help with.
Ollie.
hey sophie, it doesnt state exactly why but ill try and help, in the discussion section it merely states that the lowest ammonium release occured in the colonies that had a high respiration rate relative to gross photosynthesis, and i assume vice versa, so it is my thoughts that for the high ammonium release there was a relatively low respiration rate- photosynthesis in these colonies hence the higher amounts. Thats all i can locate at the moment, ill keep browsing though if this doesnt help.
ReplyDelete