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environmental conditions

toxicants. environmental conditions. Tjalling Jager, Olga Alda Álvarez, Evelyn Heugens, Bas Kooijman. process-based analysis. 20 ° C high food. 100%. 20 ° C low food. 80%. 10 ° C high food. 60%. r eproduction. 40%. 20%. 0%. 0. 0.1. 0.2. 0.3. 0.4. c oncentration Cd (mg/L).

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environmental conditions

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  1. toxicants environmental conditions Tjalling Jager, Olga Alda Álvarez, Evelyn Heugens, Bas Kooijman process-based analysis

  2. 20°C high food 100% 20°C low food 80% 10°C high food 60% reproduction 40% 20% 0% 0 0.1 0.2 0.3 0.4 concentration Cd (mg/L) Reproduction testing

  3. environment What is ‘sensitivity’? ‘intrinsic’ sensitivity (target site) ‘apparent’ sensitivity (e.g. ECx,t) physiology bioavailability toxicokinetics

  4. reproduction maintenance growth Dynamic Energy Budgets assimilation

  5. NEC allocation parameter blank value internal concentration DEBtox toxicokinetics  intrinsic sensitivity! target parameter  tolerance DEB model  apparent sensitivity!

  6. 5% reproduction maintenance growth Food limitation and ‘sensitivity’ assimilation ad libitum

  7. 50% maintenance Food limitation and ‘sensitivity’ assimilation limiting reproduction growth

  8. Arrhenius plot (Kooijman, 2000) How does temperature work?

  9. Example • Cd in Daphnia magna (Heugens et al.) • partial life-cycle test • 3 food levels x 3 temperatures • reproduction and survival in time • length and internal conc. at end of test

  10. DEBtox analysis • Mode of action of Cd is ‘assimilation’ • General parameters (at 20°C, high food): • von Bert. growth rate: 0.106 1/d (n.e.) • maximum length: 4.7 mm • maximum reproduction rate: 41 juv/d • Environmental factors • temperature through Arrhenius relationship • food by estimating relative ingestion rate • Estimated for each treatment • length at first repro • bioconcentration factor • intrinsic sensitivity (NEC and tolerance)

  11. Data set at 20°C, simultaneous fit

  12. Relative functional response 1 0.8 relative ingestion rate 0.6 10°C 20°C 0.4 26°C 0.2 0 0.5 1 2 algal concentration (mg C/L) Effectiveness of food limitation

  13. BCF (L/kg dwt) 4000 3500 3000 2500 2000 1500 1000 High 500 Med 0 Low 10C 20C 26C Bioavailability/Toxicokinetics

  14. Tolerance concentration (mg/kg dwt) NEC assimilation (mg/kg dwt) 25 600 500 20 400 15 300 10 200 5 100 High High Med Med 0 0 Low Low 10C 10C 20C 20C 26C 26C Intrinsic sensitivity

  15. Length at first reproduction (mm) 3.5 3 2.5 2 1.5 1 High 0.5 Med 0 Low 10C 20C 26C Physiological changes

  16. Conclusions • Intrinsic sensitivity ≠ apparent sensitivity • toxicokinetics, physiology, food-temp. interaction • Food and temperature affect Daphnia magna • toxicokinetics/bioavailability of Cd • physiology and resource allocation • intrinsic sensitivity to Cd (temperature) • Process-based models help … • to understand combined effect, • quantify intrinsic sensitivity, • and make predictions for risk assessment http://www.bio.vu.nl/thb/

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