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The DEB - theory and its applications in Ecotoxicology

Modélisation en écotoxicologie Modelleren in de ecotoxicologie Modeling in ecotoxicology. The DEB - theory and its applications in Ecotoxicology. Jacques J.M. Bedaux Dept Theoretical Biology Vrije Universiteit Amsterdam. Overview. DEB-theory DEBtox modeling frame work Some examples

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The DEB - theory and its applications in Ecotoxicology

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  1. Modélisation en écotoxicologie Modelleren in de ecotoxicologie Modeling in ecotoxicology The DEB-theory and its applications in Ecotoxicology Jacques J.M. Bedaux Dept Theoretical Biology Vrije Universiteit Amsterdam

  2. Overview • DEB-theory • DEBtox modeling frame work • Some examples • Extensions to standard DEBtox • New developments • (demo of DEBtox)

  3. DEB theory Dynamic Energy Budget theory History: It started as a statistical methodology for the study of toxic effects on Dapnnia reproduction. DEB theory presents simple mechanistic rules that describe the uptake and use of energy and nutrients (substrates, food, light) and the consequences for physiological organisation throughout an organism's life cycle

  4. DEBmodel (simple form) food reserve structure maturation maint. somatic maint. reproduction k 1-k

  5. The DEB model The model is tested on a large amount of empirical data.

  6. framework of toxicological model external concentration of chemical compound toxicological endpoint (growth, reproduction, survival)

  7. static toxicological model Log-logistic model

  8. dynamic toxicological model external concentration toxicokinetics internal concentration effects (toxicodynamics) physiological parameter blanc physiology toxicological endpoint

  9. framework standard DEBtox model external concentration toxicokinetics first-order internal concentration effects linear physiological parameter blanc physiology DEB model toxicological endpoint

  10. Example: acute test, survival external concentration C’(t) = kuc – keC(t) internal concentration Hazard rate proportional to internal concentration minus threshold h(t)  (C(t) – threshold)+ S(t) = exp(-0th(u)du) fraction of survivors

  11. internal concentration c > NEC internal threshold c = NEC c < NEC time hazard rate survivor function time time

  12. dose response curve time-dose response surface time concentration concentration • 4 parameters • NEC • elimination rate • killing rate • background mortality

  13. Example: chronic test, reproduction food assimilation reserve growth maintenance reproduction structure work eggs

  14. Effects on reproduction costs external concentration First order, dilution by growth internal concentration Energy costs per egg proportional to internal concentration minus threshold energy costs per egg reproduction rate

  15. Chronic tests: reproduction • DEBtox specifies length, internal concentration and reproduction rate • data only on reproductive output! • 4 parameters to be estimated: - NEC, tolerance concentration, - elim. rate, max. reproduction rate • numerically heavy

  16. Free software: DEBtox • Four types of toxicity tests - Survival - (Fish) Body length growth - (Daphnia) Reproduction - (Algae) Population growth • Parameter estimation, confidence intervals, likelihood profiles, statistical tests, graphical output • Windows, Unix - User friendly (Windows) - For experts (Unix) • downloadable on http://www.bio.vu.nl/thb/deb

  17. Extensions to standard DEBtox • From effects on individuals to effects on population level • Time-inhomogeneous concentrations (Alexandre Péry) • More-samples analysis

  18. From individual to population • Euler-Lotka equation mc/m0 c EC10

  19. References References on DEB: Kooijman, S.A.L.M. (2000) Dynamic Energy and Mass Budgets in Biological Systems (2nd ed) Cambrige UP. Kooijman, S.A.L.M. (2000) Quantitative aspects of metabolic organization: a discussion of concepts, Phil Trans R Soc LondB 356 Nisbet, R.M. et al (2000) From molecules tot ecosystems through dynamic energy budget models, Journal of Animal Ecology69 References on DEBtox: Kooijman, S.A.L.M. and Bedaux, J.J.M. (1996) The analysis of aquatic toxicity data, VU UP. http://www.bio.vu.nl/thb/deb

  20. Related projects • Biodegradation (DEBdeg) • Tumor incidence (DEBtum) • Food-webs

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