Population level effects of chemicals in polar bears
Published on: Mar 4, 2016
Transcripts - Population level effects of chemicals in polar bears
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 femaleBear 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 theWa…. mass [kg] at age aW…. asymptotic length model. The mechanism and Update cb 153 levelsk…. mass growth rate constant according to lactation age parameters of the lactationalA…… fitting constant, equation and par. calculate cb levels of offspring transfer in polar bears thereforevalues 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 individualsf…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 Yorkyear] (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, PhDHunting seals: every bear conducts thesis, University of Saskatchewanrandom selection of sex and age of each caught sealuntil 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 GreenlandOrganochlorine dynamics in females (Regehr et al 2010) in our research. The research was has been financially supported by the Europeanand lactational transfer to cubs: Union under the 7th Framework Programme (project acronym CREAM, contractfrom Polishuk (1999) number PITN-GA-2009-238148.) WHAT IS CREAM? ! Mechanistic Effect Models for Ecological Risk Assessment of Chemicals http://cream-itn.eu/!