Population level effects of chemicals in polar bears
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This individual-based model simulates PCB contamination levels in polar bears in East Greenland between 1994-2008. The model incorporates polar bear physiology, ecology, toxicology, and PCB data from their seal prey. Model predictions of PCB levels agree reasonably well with field data, though the model overestimates male and underestimates female contamination, suggesting lactational transfer of PCBs requires better understanding. While absolute PCB levels depend strongly on uncertain parameters, the model captures observed sex- and age-based patterns in contamination. This model will be used to simulate population effects of contaminants by imposing individual health impacts.
![Modelling population level effects of chemical contamination in polar
bear populations with special regard to PCBs:
An individual-based approach
Viola Pavlova1, Jacob Nabe-Nielsen1, Rune Dietz1,Volker Grimm2, Jens-Christian Svenning3
1National Environmental Research Institute, Department of Arctic Environment, Aarhus University, Roskilde, Denmark
2 Helmholtz Center for Environmental Research – UFZ,Department of Ecological Modelling, Leipzig, Germany
3 Ecoinformatics & Biodiversity Group, Department of Biological Sciences, Aarhus University, Denmark
In order to reconstruct the patterns of contamination levels Results & discussion
(concentrations or body burdens) that have been observed in polar bears
(Ursus maritimus) in East Greenland between the years 1994-2008 we have
constructed an individual based model that incorporates currently available Model predictions:
knowledge on polar bear physiology, ecology and toxicology and uses the Fig. 2: Prediction of mean
data on PCB levels (cb 153 only!) in their main prey, ringed seals contamination in consecutive years for
(Phoca hispida) from the same area and time period. different values of f…the field metabolic
The results allow us to asses whether our current knowledge of factor (f = 2 (left) and 4 (right), blue -
mechanisms involved in contamination exposure, dynamics of the males, red-all bears, lilac-females, year
0 = 1994, all bears older 2 yrs
contaminant in the bear body and general knowledge of bear biology is
good enough to create a realistic model, or which information needs to be
collected or verified in the field and to which parameters is the model most The absolute value of concentration greatly depends on the value of f,
sensitive. a factor which converts the basal energy requirement into field energy
This model will be later used to simulate population level effects of requirement, however its value is unknown for polar bears, comparison with
contaminants by imposing individual health effects in the modeled polar real data on contamination of polar bears would however rather support f = 3 or
bears . 4, than 2.
Methods FEMALES MALES
Fig.3: Comparison of
a) model predictions
FEMALES
MALES (f =3)
Model: non-spatial, individual based model, runs in yearly steps in Net and b) real data on
Logo platform. The agents represent individual polar bears with main polar bear
attributes: age, sex, weight, contamination & reproductive status contamination from
East Greenland 1994 -
Input data (F.Riget et al., unpubl.): Fig.1: Model scheme 2008 (data by F.Riget)
seal growth & contamination Data
a) b)
on seals SETUP
The model predicts sex and age dependent patterns in cb 153 concentration
similar to those that can be found in the nature, however the absolute values
Predict offspring
survival for this year are strongly dependent on values of parameters used for modelling lactational
transfer from mother to offspring.
Calculate energy Fig. 4: prediction of tissue concentration of cb 153 in a) 1994 (bottom left) -2008 (upper right) and
requirement of each bear b) in 2008 only, f = 3
a) b) The model tends to overestimate
age = age + 1, year = year +1
Satisfy energy demand male and underestimate female
Bear growth and energy requirement:
by hunting seals + contamination showing that the
calculate total
Wa = W (1 − e − k ( a − A) )3 cb153 consumption
loss of body burdens via lactation
is probably a too high in the
Wa…. mass [kg] at age a
W…. asymptotic length model. The mechanism and
Update cb 153 levels
k…. mass growth rate constant according to lactation age parameters of the lactational
A…… fitting constant, equation and par. calculate cb levels of offspring transfer in polar bears therefore
values from Derocher & Wiig (2002) need to be further explored.
References:
Energy: E = 365 f â‹… 70 â‹…Wa 0.75 Natural mortality Derocher A, Wiig O (2002) Postnatal growth in body length and mass of polar bears (Ursus
maritimus) at Svalbard, J. Zool., Lond. 256, 343±349,
+ breeding - create new individuals
f…factor adjusting for field Kleiber M (1961) The fire of life: an introduction to animal energetics. John Wiley & Sons, Inc.,
metabolic rate E..yearly energy need [kcal/ New York
year] (Kleiber 1961) Regehr EV, Hunter CM, Caswell H,Amstrup SC, Stirling I (2010) Survival and breeding of polar
+ adjustments for lactating females OUTPUT: Concentration of cb 153 bears in the southern Beaufort Sea in relation to sea ice, Journal of Animal Ecology 79, 117–127
in polar bears for this year
Polishuk S (1999) Organochlorine dynamics in free ranging polar bears and their cubs, PhD
Hunting seals: every bear conducts thesis, University of Saskatchewan
random selection of sex and age of each caught seal
until the energy requirement is covered => Acknowledgements:
calculate the total cb 153 increment from Population dynamics:
feeding survival & breeding rates of bears We gratefully acknowledge the consent kindly given by Frank Riget and ????? to
in Southern Beaufort Sea population: include the data on ringed seals and polar bears from Eastern Greenland
Organochlorine dynamics in females (Regehr et al 2010) in our research. The research was has been financially supported by the European
and lactational transfer to cubs: Union under the 7th Framework Programme (project acronym CREAM, contract
from Polishuk (1999) number PITN-GA-2009-238148.)
WHAT IS CREAM? !
Mechanistic Effect Models for Ecological Risk Assessment of Chemicals http://cream-itn.eu/!](https://image.slidesharecdn.com/populationleveleffectsofchemicalsinpolarbears-130205023054-phpapp01/85/Population-level-effects-of-chemicals-in-polar-bears-1-320.jpg)
Population level effects of chemicals in polar bears
- 1. Modelling population level effects of chemical contamination in polar bear populations with special regard to PCBs: An individual-based approach Viola Pavlova1, Jacob Nabe-Nielsen1, Rune Dietz1,Volker Grimm2, Jens-Christian Svenning3 1National Environmental Research Institute, Department of Arctic Environment, Aarhus University, Roskilde, Denmark 2 Helmholtz Center for Environmental Research – UFZ,Department of Ecological Modelling, Leipzig, Germany 3 Ecoinformatics & Biodiversity Group, Department of Biological Sciences, Aarhus University, Denmark In order to reconstruct the patterns of contamination levels Results & discussion (concentrations or body burdens) that have been observed in polar bears (Ursus maritimus) in East Greenland between the years 1994-2008 we have constructed an individual based model that incorporates currently available Model predictions: knowledge on polar bear physiology, ecology and toxicology and uses the Fig. 2: Prediction of mean data on PCB levels (cb 153 only!) in their main prey, ringed seals contamination in consecutive years for (Phoca hispida) from the same area and time period. different values of f…the field metabolic The results allow us to asses whether our current knowledge of factor (f = 2 (left) and 4 (right), blue - mechanisms involved in contamination exposure, dynamics of the males, red-all bears, lilac-females, year 0 = 1994, all bears older 2 yrs contaminant in the bear body and general knowledge of bear biology is good enough to create a realistic model, or which information needs to be collected or verified in the field and to which parameters is the model most The absolute value of concentration greatly depends on the value of f, sensitive. a factor which converts the basal energy requirement into field energy This model will be later used to simulate population level effects of requirement, however its value is unknown for polar bears, comparison with contaminants by imposing individual health effects in the modeled polar real data on contamination of polar bears would however rather support f = 3 or bears . 4, than 2. Methods FEMALES MALES Fig.3: Comparison of a) model predictions FEMALES MALES (f =3) Model: non-spatial, individual based model, runs in yearly steps in Net and b) real data on Logo platform. The agents represent individual polar bears with main polar bear attributes: age, sex, weight, contamination & reproductive status contamination from East Greenland 1994 - Input data (F.Riget et al., unpubl.): Fig.1: Model scheme 2008 (data by F.Riget) seal growth & contamination Data a) b) on seals SETUP The model predicts sex and age dependent patterns in cb 153 concentration similar to those that can be found in the nature, however the absolute values Predict offspring survival for this year are strongly dependent on values of parameters used for modelling lactational transfer from mother to offspring. Calculate energy Fig. 4: prediction of tissue concentration of cb 153 in a) 1994 (bottom left) -2008 (upper right) and requirement of each bear b) in 2008 only, f = 3 a) b) The model tends to overestimate age = age + 1, year = year +1 Satisfy energy demand male and underestimate female Bear growth and energy requirement: by hunting seals + contamination showing that the calculate total Wa = W (1 − e − k ( a − A) )3 cb153 consumption loss of body burdens via lactation is probably a too high in the Wa…. mass [kg] at age a W…. asymptotic length model. The mechanism and Update cb 153 levels k…. mass growth rate constant according to lactation age parameters of the lactational A…… fitting constant, equation and par. calculate cb levels of offspring transfer in polar bears therefore values from Derocher & Wiig (2002) need to be further explored. References: Energy: E = 365 f ⋅ 70 ⋅Wa 0.75 Natural mortality Derocher A, Wiig O (2002) Postnatal growth in body length and mass of polar bears (Ursus maritimus) at Svalbard, J. Zool., Lond. 256, 343±349, + breeding - create new individuals f…factor adjusting for field Kleiber M (1961) The fire of life: an introduction to animal energetics. John Wiley & Sons, Inc., metabolic rate E..yearly energy need [kcal/ New York year] (Kleiber 1961) Regehr EV, Hunter CM, Caswell H,Amstrup SC, Stirling I (2010) Survival and breeding of polar + adjustments for lactating females OUTPUT: Concentration of cb 153 bears in the southern Beaufort Sea in relation to sea ice, Journal of Animal Ecology 79, 117–127 in polar bears for this year Polishuk S (1999) Organochlorine dynamics in free ranging polar bears and their cubs, PhD Hunting seals: every bear conducts thesis, University of Saskatchewan random selection of sex and age of each caught seal until the energy requirement is covered => Acknowledgements: calculate the total cb 153 increment from Population dynamics: feeding survival & breeding rates of bears We gratefully acknowledge the consent kindly given by Frank Riget and ????? to in Southern Beaufort Sea population: include the data on ringed seals and polar bears from Eastern Greenland Organochlorine dynamics in females (Regehr et al 2010) in our research. The research was has been financially supported by the European and lactational transfer to cubs: Union under the 7th Framework Programme (project acronym CREAM, contract from Polishuk (1999) number PITN-GA-2009-238148.) WHAT IS CREAM? ! Mechanistic Effect Models for Ecological Risk Assessment of Chemicals http://cream-itn.eu/!