environmental conditions

Tjalling Jager, Olga Alda Álvarez, Evelyn Heugens, Bas Kooijman

toxicants

process-based analysis

0%

20%

40%

60%

80%

100%

0 0.1 0.2 0.3 0.4

concentration Cd (mg/L)

rep

rod

uct

ion

Reproduction testing

20°C high food

20°C low food

10°C high food

What is ‘sensitivity’?

‘apparent’sensitivity(e.g. ECx,t)

‘apparent’sensitivity(e.g. ECx,t)

‘intrinsic’sensitivity(target site)

‘intrinsic’sensitivity(target site) toxicokinetics

physiology

environment

bioavailability

Dynamic Energy Budgets

maintenance

growth

reproduction

assimilation

DEB model

DEBtox

internal concentration

allo

catio

n p

aram

eter

NEC

blank value

toler

ance

targetparameter

toxicokinetics

intrinsic sensitivity!

apparent sensitivity!

maintenance

Food limitation and ‘sensitivity’

growth

5%

reproduction

assimilation

ad libitum

maintenance

50%

Food limitation and ‘sensitivity’

growth

reproduction

assimilation

limiting

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

0.2

0.4

0.6

0.8

1

0 0.5 1 2algal concentration (mg C/L)

rela

tive

ing

esti

on

rat

e

Relative functional response

10°C

20°C

26°C

Effectiveness of food limitation

Bioavailability/Toxicokinetics

10C20C

26C

Low

Med

High

0

500

1000

1500

2000

2500

3000

3500

4000

BCF (L/kg dwt)

Intrinsic sensitivity

10C20C

26C

Low

MedHigh

0

100

200

300

400

500

600

Tolerance concentration (mg/kg dwt)

10C20C

26C

Low

MedHigh

0

5

10

15

20

25

NEC assimilation (mg/kg dwt)

Physiological changes

10C20C

26C

Low

Med

High

0

0.5

1

1.5

2

2.5

3

3.5

Length at first reproduction (mm)

Conclusions

Intrinsic sensitivity ≠ apparent sensitivity• toxicokinetics, physiology, food-temp. interaction

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

DEB model

targetparameter

toxicokinetics

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