Evaluation of the efficacy of extrapolation population modeling to predictthe dynamics of Americamysis bahia populations in the laboratory

An age-classified projection matrix model has been developed to extrapolate the chronic (28-35 d) demographic responses of Americamysis bahia (formerl y Mysidopsis bahia) to population-level response. This study was conducted to evaluate the efficacy of this model for predicting the population behavi or of A. bahia held (for more than three generations) under controlled labo ratory exposure conditions. The research involved the performance of a stan dard life-cycle test and a multigenerational (greater than three mysid gene rations, 55 d) assay using A. bahia to experimentally evaluate model predic tions regarding population-level risks of chemical exposure. The organic co mpound para-nonylphenol was chosen as the chemical stressor in these assays . This compound is a ubiquitous contaminant and suspected endocrine disrupt er. Utilizing data obtained during the standard life-cycle test, aggregate estimates of population growth rare (lambda) and measured p-nonylphenol con centration were used to develop an exposure-response model of population-le vel effects. These estimates provided the basis of predictions for the long -term dynamics of mysid populations exposed to p-nonylphenol. The veracity of the mysid population model was evaluated through quantitative comparison s of model predictions based on the life-cycle test with dynamics of the ex perimental populations (multigenerational assay results). The results indic ate that the population model was able to project within a few micrograms p er liter the concentration where population-level effects would begin to oc cur (projected 16 mug/L from the model vs measured 19 mug/L from the multig enerational assay).