1、New Developments in the Marine Nitrogen Cycle,1. Basic knowledge & Introduction 2. Increased in denitrification estimates and its consequence 3. Difficulties in the marine nitrogen cycle research 4. New techniques to explore nitrogen cycle4.1 FISH and working hypothesis4.2 Nano-SIMS working hypothes
2、is,Outline,1. Basic knowledge & Introduction,N,NO3,NO2,NH4,N2,Organic nitrogen,Fixed N,Classic nitrogen reaction web (Brandes, 2007),six terms to describe the marine nitrogen cycle: N2 fixation, riverine inputs, atmospheric fallout, sediment organic matter burial, and water column and sedimentary de
3、nitrification.,Early marine nitrogen studies focused on the role of N as a primary productivity-limiting element. Redfield Ratio provided a simple metric to determine whether nitrogen or phosphorus would limit overall levels of primary productivity in a particular ecosystem.N*= NO3 - 16PO4 + 2.9 Rep
4、resents the deviations from RR reflect non-Redfield biological nutrient inputs,1. Basic knowledge & Introduction,N*,Nitrogen fixation,denitrification,2.Increased in denitrification estimates and its consequence,Classic nitrogen reaction web,Diagram of the nitrogen cycle as it is understood today.,(B
5、randes et al, 2007),Denitrification is the only way to loss N,Many processes were found tocontributed for N loss,2.Increased in denitrification estimates and its consequence,A logical consequence of the increase in denitrification estimates has been to create difficulties in achieving balanced marin
6、e fixed nitrogen budgets, which would require higher globally integrated nitrogen fixation rates.Future work will pay special attention to three areas: 1.new processes leading to nitrogen losses, 2.sites of nitrogen fixation, 3.an assessment to balance the preindustrial marine N budget.,1.Marine mic
7、robes other than Trichodesmium may contribute substantial inputs of newly fixed N that would not be represented in any previous biological estimates, which leads to underestimate of nitrogen fixation. But it is difficult to sort the different algae, until the advent of FISH(fluorescence in situ hybr
8、idization).,2.Difficulties in the marine nitrogen cycle research,3.New techniques to solve the problems,Three groups of cells (Prochlorococcus, Synechococcus and picoeukaryotes) can be distinguished. For example Synechococcus is characterized by the double fluorescence of its pigments: orange for ph
9、ycoerythrin (PE) and red for chlorophyll.,http:/en.wikipedia.org/wiki/Photosynthetic_picoplankton,Autofluorescent cells,SYTO-13 stained cells,Fluorescence-activated cell sorting (FACS),Cell Sorting (ink-jet graphic printing and electrostatic deflection),Droplet sorting 25,000/s,Fawcett et al. (2011)
10、 Nature geoscience 4: 717-722.,Assimilation of upwelled nitrate by small eukaryotes in the Sargasso Sea (Fawcett et al., 2011),8L water samples,47 mm 0.4 mm PC membranes,Step 1. Cells (particulate nitrogen) collection and flow cytometric sorting,Collection (100 mm Hg),Agitation,Step 2: Oxidation of
11、PN to NO3-,(Elemental analyzer) (Gas chromatography-isotope Mass spectrometer),Remove the filter,Filtration,(Flow Cytometer) sorting,4mL ( 0.2 mm) seawater,Prochlorococcus Synechococcus Eukaryotic algae Heterotrophic bacteria detritus,5 mL cells water,Collection,Filtrates,30 mm mesh,25 mm 0.2 mm PC
12、membranes,Sonication,2 mL DI water,60 min,Remove the filter,Persulphate oxidation,NO3-,PN,(Chemiluminescent analyzer),Denitrifier method,NO3-,15N,Fawcett et al. (2011) Nature geoscience 4: 717-722.,Figure 1: Important forms of nitrogen in the Sargasso Sea.,Figure 2: Abundances and nitrogen isotope r
13、atios of populations sorted by flow cytometry.,Fawcett et al. (2011) Nature geoscience 4: 717-722.,Figure 3: Changes to previous view of Sargasso Sea nitrogen cycling.,Fawcett et al. (2011) Nature geoscience 4: 717-722.,Nfixation,Light 15N2O,Working hypothesis Simultaneously enhanced GHG release whi
14、le strengthening biopump,0m,Model & 15N,18O,N*,(15,18),biopump15NPN,50m,High N/P,N2O,POM,diatom150m500m,heavier,Low N/P 15NO3=551,Trap 15N=51,SIMS,14N,Modified from Myrold et al. 2011,NanoSIMS,nanoSIMS,Assets: Stable isotopes Highly sensitive Single cell resolution (lateral: 33 nm; verticla: few ato
15、mic layers) Drawbacks: Very expensive equipment ( 2 million ) Intricate to perform,NanoSIMS: Applied on many fields,Biomineralization Environmental Microbiology Nitrogen fixation in the deep-sea Assimilatory ability of organic carbon in autotrophic AOA Plant / Soil Cell Biology Materials Geology & E
16、nvironment The sulphur-based metabolisms for Palaeoarchean microbial ecosystems. Cosmochemistry Intrumentation -FISH (fluorescence in situ hybridization),Deep-sea anaerobic methane-oxidizing archaea fix N2,Incubated with 15N2,(Dekas et al., Science, 2009),Sediment associated processes Mn+/MnO2 parti
17、cipation,Working hypothesis,Suspended particle creates huge amounts of particulate micro-niche with various redox degree in oxygenated water column to proceed N transformation,Particle associated nitrifier,CARD-FISH for nitrifier,Fussel et al. (2011),Aggregate associated nitrifier,Green : nitrifier Blue : All microorganism,
