Dynamic Energy Budgetsi.r.t. population effects of toxicants

Tjalling JagerDept. Theoretical Biology

Contents

What DEB is not … What is DEB? Advantages of using DEB

Example life-cycle datasetBindesbøl et al (2007)• copper in Dendrobaena octaedra• size, survival, cocoons over 20 weeks• here, only [Cu] > 80 mg/kg

What DEB is not

DEB is not a population model DEB is not needed to estimate population effects

DEB-less analysis

conc. hatching %

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hatching time: 92 days

DEB-less analysis

conc. hatching %

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hatching time: 92 days

Intrinsic rate of increase

2-stage modelsplined, Euler-Lotka

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What have we achieved?

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longer exposure time,

untested concentrations,

time-varying conditions,

temperature,

food limitation,

other species,

other compounds …

Integrated effects on survival and reproduction over time … … for test concentrations and test conditions … Can we make educated inter- and extrapolations?

What is DEB?

Quantitative theory; ‘first principles’• time, energy and mass balance

Life-cycle of the individual• links levels of organisation: molecule

ecosystems

Comparison of species• body-size scaling relationships; e.g., metabolic

rate

Fundamental to biology; many practical applications

• (bio)production, (eco)toxicity, climate change, …

Kooijman (2000)

Kooijman (in press)

Bookkeeping rules …

growth

reproduction

feeding

maintenance

maturation

Toxicants in DEB

externalconcentration

(in time)

toxico-kinetics

toxico-kinetics internal

concentrationin time

life-historytraits

one-compartment model, accounting for changes in body size

Toxicants in DEB

externalconcentration

(in time)

toxico-kinetics

toxico-kinetics internal

concentrationin time DEB

parametersin time

life-historytraits

ingestion ratemaintenance rate coeff.egg costsetc. …

Toxicants in DEB

externalconcentration

(in time)

toxico-kinetics

toxico-kinetics internal

concentrationin time DEB

parametersin time

DEBmodel

DEBmodel

life-historytraits

KM-DEB (Klok et al, 1996)DEBtox (Kooijman & Bedaux, 1996)DEB3 (Jager et al, subm.)

Toxicants in DEB

externalconcentration

(in time)

toxico-kinetics

toxico-kinetics internal

concentrationin time DEB

parametersin time

DEBmodel

DEBmodel

life-historytraits

growth, time to reproduction, reproduction ratemortality etc. …

DEB analysis of dataSimultaneous fit size and repro data

MoA: decrease in ingestion rate

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DEB analysis of data

Assume size-dependent feeding limitation (Jager et al, 2005)

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Parameter estimates

externalconcentration

(in time) toxico-kinetics

toxico-kinetics

internalconcentration

in time metabolicprocesses

in timeDEB

model

DEBmodel

life-historytraits

TK pars tox pars DEB pars

to population model …

Population effects

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2-stage modelsplined, Euler-Lotka

DEB, Euler-Lotka

no-effects

What’s different?

effectsdata individuals

effectsdata individuals

populationconsequences

populationconsequences

modelparameters

modelparameters

extrapolatedparameters

extrapolatedparameters

DEB-less

DEB

Educated extrapolation

externalconcentration

(in time) toxico-kinetics

toxico-kinetics

internalconcentration

in time metabolicprocesses

in timeDEB

model

DEBmodel

life-historytraits

TK pars tox pars DEB pars

time-varying concentrations

Educated extrapolation

externalconcentration

(in time) toxico-kinetics

toxico-kinetics

internalconcentration

in time metabolicprocesses

in timeDEB

model

DEBmodel

life-historytraits

TK pars tox pars DEB pars

less food in environment

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Food limitation

food 100%

food 90%

Educated extrapolation

externalconcentration

(in time) toxico-kinetics

toxico-kinetics

internalconcentration

in time metabolicprocesses

in timeDEB

model

DEBmodel

life-historytraits

TK pars tox pars DEB pars

size-dependent feeding limitations

Food limitation juveniles

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Food limitation juveniles

food 100%

food 90%

Educated extrapolation

externalconcentration

(in time) toxico-kinetics

toxico-kinetics

internalconcentration

in time metabolicprocesses

in timeDEB

model

DEBmodel

life-historytraits

TK pars tox pars DEB pars

other compounds (related)

externalconcentration

(in time) toxico-kinetics

internalconcentration

in time

Educated extrapolation

externalconcentration

(in time) toxico-kinetics

toxico-kinetics

internalconcentration

in time metabolicprocesses

in timeDEB

model

DEBmodel

life-historytraits

TK pars tox pars DEB pars

other compounds (mixtures)

Educated extrapolation

externalconcentration

(in time) toxico-kinetics

toxico-kinetics

internalconcentration

in time metabolicprocesses

in timeDEB

model

DEBmodel

life-historytraits

TK pars tox pars DEB pars

other (related) species

What’s the use of DEB?

In-depth interpretation of effects on individual• all endpoints over time in one framework• indicates experimental ‘problems’• mechanism of action of compound

DEB is essential for inter- and extrapolation• e.g., extrapolation to field conditions• ‘repair’ experimental artefacts

Natural link with different population approaches• simple (e.g., Euler-Lotka and matrix models)• more complex (e.g., IBM’s)

But …

Strong (but explicit) assumptions are made• on metabolic organisation• on mechanisms of toxicity

Elaborate DEB models require strong data• growth, repro and survival over (partial) life cycle• e.g., Daphnia repro protocol extended with size

Almost every analysis raises more questions• difficult to perform on routine basis

Interesting point raised by DEB3 …• hatching time and hatchling size can be affected by stress

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Vacancies• PhD student, Marie Curie training network (CREAM)

Courses• International DEB Tele Course 2011

Symposia• 2nd International DEB Symposium 2011 in Lisbon

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