IP07 Population-Level Ecological Risk Assessment
B113 & B114
8:00 AM - 12:00 PM, Wednesday
(IP052) Use of population growth effect measurement and modelling to provide quantitative information of value for risk assessment.
Spurgeon, D1, Svendsen, C1, Hankard, P1, 1 Centre for Ecology and Hydrology, Monks Wood, Cambs, UK
ABSTRACT- Population growth rate can be assessed either by measuring vital rates and using modelling approaches to estimate the intrinsic rate of population increase (rm), or in a technically more simple approach by measuring changes in population size over time and using this data to estimate the instantaneous rate of population increase (ri). In this study we describe the use of both approaches. Demographic modelling is applied to estimate rm in the earthworm Lumbricus rubellus exposed to metal contaminated soils along a contamination gradient. This data is then used to model the long-term effects of changes in rm on the size and persistence of earthworm populations inhabiting each contaminated soil. Instantaneous rate of population increase is studied in the Collembola Folsomia candida exposed to cadmium, copper, pyrene and chlorpyrifos in artificial soil. Traditional toxicity values LC50, EC50Juvenile and NOECs were calculated for each chemical and ri determined. Comparison of the relative toxicity of the four chemicals indicated that chlorpyrifos had the lowest values and was thus the most toxic, followed by pyrene, cadmium and copper. Significant changes in ri were seen to closely follow changes in the sub-lethal parameter measured (juvenile production) and showed populations in decline at concentrations as low as 40% of the LC50. Mode of action affected the relationship between acute and population levels effects, with population changes occurring at concentrations closer to the LC50 for specifically acting chemicals The study showed that both rm and ri are good measure of population response and we conclude the statistic gives a better understanding of effects on a population than the sole use of traditional critical effect estimates.
Key words: mode of action, Springtails, population growth