Dynamic Energy Budgets i.r.t. population effects of toxicants Tjalling Jager Dept. Theoretical Biology

Contents  What DEB is not …  What is DEB?  Advantages of using DEB Example life-cycle dataset Bindesbøl 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 % time (days) fraction survival cumulative reproduction time (days) 12 hatching time: 92 days

DEB-less analysis conc.hatching % time (days) fraction survival time (days) cumulative reproduction hatching time: 92 days

Intrinsic rate of increase 2-stage model splined, Euler-Lotka concentration (mg/kg soil) population growth rate (d -1 ) 12

What have we achieved? 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 external concentration (in time) toxico- kinetics toxico- kinetics internal concentration in time life-history traits one-compartment model, accounting for changes in body size

Toxicants in DEB external concentration (in time) toxico- kinetics toxico- kinetics internal concentration in time DEB parameters in time life-history traits ingestion rate maintenance rate coeff. egg costs etc. …

Toxicants in DEB external concentration (in time) toxico- kinetics toxico- kinetics internal concentration in time DEB parameters in time DEB model DEB model life-history traits KM-DEB (Klok et al, 1996) DEBtox (Kooijman & Bedaux, 1996) DEB3 (Jager et al, subm.)

Toxicants in DEB external concentration (in time) toxico- kinetics toxico- kinetics internal concentration in time DEB parameters in time DEB model DEB model life-history traits growth, time to reproduction, reproduction rate mortality etc. …

DEB analysis of data Simultaneous fit size and repro data MoA: decrease in ingestion rate time (days) body length time (days) cumulative offspring per female

DEB analysis of data Assume size-dependent feeding limitation (Jager et al, 2005)

Parameter estimates external concentration (in time) toxico- kinetics toxico- kinetics internal concentration in time metabolic processes in time DEB model DEB model life-history traits TK parstox parsDEB pars to population model …

Population effects concentration (mg/kg soil) population growth rate (d -1 ) 2-stage model splined, Euler-Lotka DEB, Euler-Lotka no-effects

What’s different? effects data individuals effects data individuals population consequences population consequences model parameters model parameters extrapolated parameters extrapolated parameters DEB-less DEB

Educated extrapolation external concentration (in time) toxico- kinetics toxico- kinetics internal concentration in time metabolic processes in time DEB model DEB model life-history traits TK parstox parsDEB pars time-varying concentrations

Educated extrapolation external concentration (in time) toxico- kinetics toxico- kinetics internal concentration in time metabolic processes in time DEB model DEB model life-history traits TK parstox parsDEB pars less food in environment

concentration (mg/kg soil) population growth rate (d -1 ) Food limitation food 100% food 90%

Educated extrapolation external concentration (in time) toxico- kinetics toxico- kinetics internal concentration in time metabolic processes in time DEB model DEB model life-history traits TK parstox parsDEB pars size-dependent feeding limitations

Food limitation juveniles

concentration (mg/kg soil) population growth rate (d -1 ) Food limitation juveniles food 100% food 90%

Educated extrapolation external concentration (in time) toxico- kinetics toxico- kinetics internal concentration in time metabolic processes in time DEB model DEB model life-history traits TK parstox parsDEB pars other compounds (related)

external concentration (in time) toxico- kinetics internal concentration in time Educated extrapolation external concentration (in time) toxico- kinetics toxico- kinetics internal concentration in time metabolic processes in time DEB model DEB model life-history traits TK parstox parsDEB pars other compounds (mixtures)

Educated extrapolation external concentration (in time) toxico- kinetics toxico- kinetics internal concentration in time metabolic processes in time DEB model DEB model life-history traits TK parstox parsDEB 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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