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

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

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

Dynamic Energy Budgets reproduction assimilation growth maintenance

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

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

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

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

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

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)

Data set at 20°C, simultaneous fit

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

Bioavailability/Toxicokinetics Low Med High 500 1000 1500 2000 2500 3000 3500 4000 BCF (L/kg dwt)

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

Physiological changes Low Med High 0.5 1 1.5 2 2.5 3 3.5 Length at first reproduction (mm)

Conclusions http://www.bio.vu.nl/thb/ 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/