Dr. Nicola Wannicke
- Nitrogen fixation and release of nitrogen compounds by cyanobacteria
- Identification, cultivation and determinatiom of physological parameter of phytoplankton
Biological impacts of ocean acidification (phase II)
Subproject 1.4 Diazotrophic nitrogen fixation and nitrogen cycling within the plankton community.
We aim to better understand the uptake of nitrogen by primary producers (especially diazotrophic cyanobacteria), as well as the release of nitrogenous compounds under different pCO2 concentrations. Community specific uptake will be done using stable isotope tracer addition and mass spectrometry analysis. Different nitrogenous tracer will be used (15N2 gas, 15N-amino acids) to address different aspects of nitrogen cycling. Cell specific nitrogen uptake and processing as well as cell specific metabolic rates can be investigated using the IOW facility of the NanoSIMS. This method will help to understand cell specific differences based upon changes in the specific genome making specific genotypes more efficient within one species.
Moreover, the time depended transfer of diazotrophic nitrogen into the bacterial community or towards higher trophic levels will be analysed using stable isotope tracer addition.
Furthermore, the impact of ocean acidification on toxin production (mainly Nodularin and Microscystin) will be determined using HPLC and ELISA techniques.
Two joint Mesocosm experiments will be carried out by the whole Consortium 1 (Pelagic ecosystems under ocean acidification: ecological, biogeochemical, and evolutionary responses) at which our subproject participates. KOSMOS I (Kiel Offshore Mesocosms for Future Ocean Simulation) will take place in 2013 in Gullmar Fjord near Kristineberg, Sweden , KOSMOS II 2014 at Gran Canary.
We propose to test the following hypotheses:
- Does the theory of reduction of carbon concentration mechanism hold true to explain the mechanisms of increased primary production and N2 fixation in cyanobacteria as a response to ocean acidification and temperature increase?
- Will the rate and stoichiometry of organic matter turn-over and nutrient cycling become affected? What are the tipping points?
- Can relationships between environmental constraints e.g. OA and toxicity be developed?
- Do microbes (autotrophs and heterotrophs) respond to OA along gradients of natural variability as typical for the Baltic Sea (alkalinity, DIC, CO2, T, nutrients)?
- Is the community composition of cyanobacteria blooms sensitive to OA?