Modeling the Influence of Environmental Heterogeneity on Heavy Metal Exposure Concentrations for Terrestrial Vertebrates in River Floodplains

Abstract

To analyze the influence of environmental heterogeneity on heavy metal exposure concentrations for terrestrial vertebrates in river floodplains, a spatially explicit exposure model has been constructed (SpaCE-model: Spatially explicit cumulative exposure model). This model simulates the environmental use of individual organisms by selecting model cells to be foraged in within a multicelled, heterogeneous landscape. Exposure durations and exposure concentrations are calculated for the selected cells, whereby exposure concentrations are dependent on the availability and contaminant concentrations of different diet items in each cell. The model was applied to a selection of 10 terrestrial vertebrate species, including six small mammalian and four top predator species. It was parameterized for cadmium contamination in a 285-ha, embanked floodplain area along the Rhine River in The Netherlands. Simulations of 1,000 individuals for each species resulted in intraspecies variation in exposure concentrations of between 11 and 39%, with the smallest values generally corresponding to the species with the largest home ranges. Comparison of the model results with cadmium concentrations measured in four of the species from the study area showed that the predicted variation accounted for 12 to 16% of the variation in the measurements. This indicates that environmental heterogeneity governs a minor part of the variation in metal exposure concentrations that can actually be observed in river floodplains.

Modeling zinc regulation in small mammals

“…The SpaCE model, developed by Schipper et al [14], is a tool to assess dietary exposure of terrestrial vertebrates to cumulative chemical stressors. The SpaCE model, developed by Schipper et al [14], is a tool to assess dietary exposure of terrestrial vertebrates to cumulative chemical stressors.…”

“…However, of the metals addressed by toxicokinetic models, only chromium is an essential metal, and for zinc in either human or animal species no simple toxicokinetic models have been developed [13]. The model was incorporated into the Spatially Explicit Cumulative Exposure (SpaCE) model [14] to verify whether it adequately predicts the zinc exposure levels for small mammals living in a zinc-contaminated floodplain in the Netherlands. A mechanistic formula for zinc uptake and elimination was deduced from information on the kinetics of zinc.…”

Uncertainty in hydromorphological and ecological modelling of lowland river floodplains resulting from land cover classification errors

“…Through uptake in vegetation and soil-dwelling invertebrates, these metals may enter food chains and potentially induce toxic effects in the organisms exposed. Although the effects of metal exposure are mostly subordinate to influences of other ecosystem stressors, notably flooding (Schipper et al, 2008b(Schipper et al, , 2011, ecotoxicological hazards cannot be excluded for certain susceptible species ( Van den Brink et al, 2003;Schipper et al, 2008a).…”

“…Over the past decades, much effort has been put into the development of models to quantify the impacts of hydrological changes and landscaping measures on flood risk and floodplain ecology. Hydromorphological models provide estimates of peak water levels and sediment deposition (RWS, 2007;Bates et al, 2010), while ecological models characterize habitat suitability, biodiversity (Lenders et al, 2001;Schipper et al, 2008a) and ecosystem services (Nelson et al, 2009). Such models are routinely used in environmental impact assessments of floodplain restoration projects with landscaping measures that aim to reduce the flood risk and improve the ecological quality of the riverine area.…”

“…In the context of ecological modelling, land cover maps provide essential information to define and delineate habitat (e.g. Schipper et al, 2008a). Establishing accurate land cover maps of large floodplain areas would require extensive field survey, and therefore remote sensing data are used for this purpose.…”