slide1 n.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
Spatial heterogeneity in marine ecology : two examples PowerPoint Presentation
Download Presentation
Spatial heterogeneity in marine ecology : two examples

Loading in 2 Seconds...

play fullscreen
1 / 32

Spatial heterogeneity in marine ecology : two examples - PowerPoint PPT Presentation


  • 151 Views
  • Uploaded on

NVTB Symposium 7 Nov 2006. Spatial heterogeneity in marine ecology : two examples. Jean-Christophe POGGIALE. Centre d’Océanologie de Marseille (OSU) Laboratory of Marine Microbiology, geochemistry and Ecology (UMR 6117) Case 901 – Campus de Luminy – 13288 Marseille Cedex 09

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

Spatial heterogeneity in marine ecology : two examples


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
    Presentation Transcript
    1. NVTB Symposium 7 Nov 2006 Spatial heterogeneity in marine ecology : two examples Jean-Christophe POGGIALE Centre d’Océanologie de Marseille (OSU) Laboratory of Marine Microbiology, geochemistry and Ecology (UMR 6117) Case 901 – Campus de Luminy – 13288 Marseille Cedex 09 poggiale@com.univ-mrs.fr

    2. NVTB Symposium 7 Nov 2006 Mathematical Ecology Dr. David NERINI Dr. Claude MANTE Caroline TOLLA (PhD) Marie EICHINGER (PhD) Dr. Anne-Françoise YAO

    3. NVTB Symposium 7 Nov 2006 EXAMPLE 1 NITROGEN CYCLE IN MARINE SEDIMENTS: Impact of heterogeneity on degradation processes intensity

    4. NO3 N2 Diffusion Assimilatrice reduction NO3 NO2 NH4 Norg Nitrification Ammonification Diffusion NO3 NO2 NH4 N2O N2 Ammonification Denitrification NVTB Symposium 7 Nov 2006 Nitrogen cycle in marine sediments Column water Oxic sediment Anoxic sediment

    5. NVTB Symposium 7 Nov 2006 Usual formulations in biogeochemical models

    6. NVTB Symposium 7 Nov 2006 Role of bioturbation • Bioturbation : reworking activities and displacements induced by macro – organisms in sediments • Transport of particles, solutes and microorganisms • Presence of oxic zones in the anoxic layer and of anoxic zones in the oxic layer (spatial heterogeneity) • Permanent modifications of the micro-organisms environment (temporal heterogeneity) • Source of temporal and spatial heterogeneity How does it affect the fate of organic matter?

    7. Oxic layer NVTB Symposium 7 Nov 2006 Example of experiments Anoxic layer 45 days 45 days 45 days N2 oxic anoxic RedOx oscillations

    8. NVTB Symposium 7 Nov 2006 Conclusions of experiments • Quantification of nitrogen mineralization (organic nitrogen transformed in NH4, NO3, N2O or N2) • Nitrogen mineralization in oxic conditions>1.6 * nitrogen mineralization in anoxic conditions • Nitrogen mineralization in oscillating conditions>4.8 * nitrogen mineralization in oxic conditions

    9. INTERMEDIATE PROCEDURE • define a model which describes the degradation processes; • reproduce temporal variations with a periodic forcing associated to RedOx oscillations. NVTB Symposium 7 Nov 2006 How to proceed to understand the previous result? • define a model which describes the degradation processes; • couple this model with a bioturbation model which reproduces the spatial and temporal heterogeneity.

    10. NVTB Symposium 7 Nov 2006 Modelling bioturbation Cochran model - 1985 C C C z z z

    11. Day 0: luminophores added (4 g; 80-150 µm) Day 9: macrofauna 1-cm thick slicing sieving Sediment and fluorescent particles z drying + homogeneization MUC Core (diam.: 10 cm) [Luminophores] = f (z,t) • Biodiffusive profiles • Cochran (1985) ¶ ¶ Luminophore counting under UV light C C = D 2 b ¶ ¶ NVTB Symposium 7 Nov 2006 Quantification by luminophores technique t x ²

    12. NVTB Symposium 7 Nov 2006 Quantification with 2D-optical system T0: luminophores added (2 g; 80-150 µm) time serie pictures z Plexiglas squared core from Usnel Box corer May 2001 cruise

    13. NVTB Symposium 7 Nov 2006 Example of images 0 18 Time (h) Same kind of images for oxygen, nitrate, pH, …

    14. NVTB Symposium 7 Nov 2006 Biogeochemical models

    15. BAC (%) POC (mmol/l) O2 (µmol/l) NO3 (µmol/l) 2 j 4 j 8 j 16 j NVTB Symposium 7 Nov 2006 Example of numerical simulations

    16. NVTB Symposium 7 Nov 2006 Conclusions and perspectives • Need a more biologically relevant formulation • Micro-organisms respond to environmental perturbations at individuals levels • DEB theory permits to: • take individuals level into account in population dynamics models, • describe the role of organisms on elements cycles by using mass balance arguments, • maintain a trade off between biological realism and required simplicity of models at the ecosystem level • Use a DEB approach to explain how a heterogeneous environment may support higher degradation rates than homogeneous environment

    17. NVTB Symposium 7 Nov 2006 EXAMPLE 2 COMPETITION IN THE COLUMN WATER: Impact of heterogeneity on biodiversity

    18. NVTB Symposium 7 Nov 2006 The problem position • Exclusion principle : no more than one species on one limiting factor in homogeneous environment, the other species are outcompete • Plankton paradox (Hutchinson, 1961) • Lots of explanations, a few of them are really satisfying from a theoretical point of view

    19. NVTB Symposium 7 Nov 2006 Temporal heterogeneity induced by physics Availability of nutrients at individuals scale Time (sec.)

    20. NVTB Symposium 7 Nov 2006 A first approximation : Oscillating conditions

    21. sp 1 excludes sp 2 Region of coexistence m1/d1 Extinction sp 2 excludes sp 1 m2/d2 NVTB Symposium 7 Nov 2006 A first approximation : Oscillating conditions (Hsu, 1980, Smith, 1980) H. Smith, 1997 : monospecific Droop Model

    22. NVTB Symposium 7 Nov 2006 Surge uptake Some experiments suggest that absorption rate increases with reserve at a short time scale

    23. NVTB Symposium 7 Nov 2006 Competition in heterogeneous conditions

    24. NVTB Symposium 7 Nov 2006 Time scales and mathematical simplifications

    25. NVTB Symposium 7 Nov 2006 Competition in fluctuating food conditions

    26. NVTB Symposium 7 Nov 2006 Competition in fluctuating food conditions

    27. NVTB Symposium 7 Nov 2006 Competition in fluctuating food conditions

    28. NVTB Symposium 7 Nov 2006 Competition in fluctuating food conditions

    29. NVTB Symposium 7 Nov 2006 Competition in fluctuating food conditions

    30. NVTB Symposium 7 Nov 2006 Competition in fluctuating food conditions

    31. NVTB Symposium 7 Nov 2006 Competition in fluctuating food conditions

    32. NVTB Symposium 7 Nov 2006 CONCLUSION • Fast response of individuals to food supply fluctuations • Intermittency of food supply simulation : long range memory processes (fractional brownian processes) • Mechanistic basis of the population dynamics model : DEB theory