A dynamic biophysical fugacity model of the movement of a persistent organic pollutant in Antarctic marine food webs

Abstract

Environmental contextPersistent organic pollutants (POPs) are potentially toxic chemicals capable of long distance transport and are often found far from their source. Little is known of their behaviour in Antarctica, where the marine plankton food web is driven by strong seasonal variations in solar radiation. Here the first dynamic coupled ecosystem–fugacity model to describe how POPs distribute through the Antarctic environment is presented. The model is used to identify the important processes that govern the presence of hexachlorobenzene in Antarctic plankton. AbstractPolar regions can be repositories for many persistent organic pollutants (POPs). However, comparatively little is known of the movement and behaviour of POPs in Antarctic ecosystems. These systems are characterised by strong seasonal effects of light on plankton dynamics. This work describes a mass-conserving, fugacity-based dynamic model to describe the movement of POPs in the Antarctic physical and plankton systems. The model includes dynamic corrections for changes in the population volumes and the temperature dependence of the fugacity capacities, and was developed by coupling a dynamic Nutrient–Phytoplankton–Zooplankton–Detritus (NPZD) ecosystem model to fugacity models of the chemistry and biology of the Southern Ocean. The model is applied to the movement of hexachlorobenzene, a POP found in the Antarctic environment. The model predicts that the burden of HCB in the plankton varies with the seasonal cycle in Antarctic waters, and induces a seasonal variation in the biomagnification factor of zooplankton. This suggests that time series of POP concentrations in Antarctic biotic and abiotic systems should be measured over complete seasonal cycles. Furthermore, detritus is shown to be a key contributor to the movement of POPs in polar environments, linking physical and biological components of the model.