"Simulation of the population-level effect of 4-nonylphenol on the wild Japanese medaka (Oryzias latipes)"

Meng Yaobin, LIN Bin-Le, Mamoru Tominaga, Junko Nakanishi 

National Institute of Advanced Industrial Science and Technology

  ECOLOGICAL MODELLING, Vol.197 pp.350-60 (2006/4) 

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Abstract

Here we established a structured matrix model for wild Japanese medaka (Oryzias latipes) and predicted the population-level effects of 4-nonylphenol (4-NP) using a stochastic simulation approach. In the model, the natural fecundity and mortality rates of wild medaka were considered inhibited by 4-NP, based on Weibull dose-response models estimated from a full life-cycle toxicity test. The matrix model was simulated according to three scenarios: 1) stochastic daily growth under optimal conditions, 2) stochastic annual growth under seasonal variation conditions, and 3) quasi-extinction over 3 years under density-regulation. Accordingly, a finite population growth rate, , was applied as an endpoint in the first and second scenarios and a quasi-extinction risk in the third scenario. The median and 95% confidence interval (CI) of 4-NP concentrations corresponding to =1 (C=1) in the first and second scenarios were 26.8 g/L (CI: [20.2, 33.1]g/L) and 17.3 g/L (CI: [16.5, 18.0]g/L), respectively. At low exposure concentrations the changes of quasi-extinction risk to concentration were complex, but the quasi-extinction risk climbed up quickly if the exposure concentration approached C=1.The influence of uncertainties were discussed, and the ignorance whether adult madaka should be considered inhibited by 4-NP or not was found affecting the population-level effects significantly, whereas the uncertainties in fecundity rate and mortality rate exhibited relatively weak influence. This study demonstrated an application of C=1 in a stochastic sense as population-level ecological risk assessment (PLERA) endpoint in chemical risk management. 

Keywords

Simulation,4-nonylphenol,medaka,population-level effect