toxicants environmental conditions processbased analysis Tjalling Jager Olga

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

Reproduction testing 20°C high food reproduction 100% 20°C low food 80% 10°C high food 60% 40% 20% 0% 0 0. 1 0. 2 0. 3 concentration Cd (mg/L) 0. 4

What is ‘sensitivity’? environment ‘intrinsic’ sensitivity (target site) bi oa va i to xi ph co la bi ki n ys i et ic y s lit ‘apparent’ sensitivity (e. g. ECx, t) ol og y

Dynamic Energy Budgets assimilation reproduction maintenance growth

DEBtox toxicokinetics allocation parameter intrinsic sensitivity! target parameter NEC ce n ra le to DEB model blank value internal concentration apparent sensitivity!

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

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

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

Example Ø 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 Ø Mode of action of Cd is ‘assimilation’ Ø General parameters (at 20°C, high food): • von Bert. growth rate: • maximum length: • maximum reproduction rate: 0. 106 1/d (n. e. ) 4. 7 mm 41 juv/d Ø Environmental factors • temperature through Arrhenius relationship • food by estimating relative ingestion rate Ø 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 Relative functional response relative ingestion rate 1 0. 8 0. 6 10°C 20°C 0. 4 26°C 0. 2 0 0. 5 1 2 algal concentration (mg C/L)

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

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

Physiological changes Length at first reproduction (mm) 3. 5 3 2. 5 2 1. 5 1 High Med 0. 5 0 10 C Low 20 C 26 C

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