1 / 32

Spatial heterogeneity in marine ecology : two examples

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

pascal
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. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

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

More Related