Metacommunities, metaecosystems and the environmental fate of chemical contaminants

1. Although pollution is a major driver of ecosystem change, models predicting the environmental fate of contaminants suffer from critical uncertainties related to oversimplifying the dynamics of the biological compartment. 2. It is increasingly recognized that contaminant processing is an outcome of ecosystem functioning, that ecosystem functioning is contingent on community structure and that community structure is influenced by organismal dispersal. We propose a conceptual organization of the contribution of organismal dispersal to local contaminant fate. Direct dispersal effects occur when the dispersing organism directly couples contaminant stocks in spatially separate ecosystems by transporting contaminants in its biomass. Indirect dispersal effects occur when the dispersing organism indirectly influences contaminant fate via community assembly. This can occur either when the dispersing organism is a contaminant processor or when the dispersing organism alters, via species interactions, the abundance of contaminant biotransporters or processors already established in the ecosystem. The magnitude of direct and indirect dispersal effects is modulated by many factors, including other contaminants. These will influence population growth rates of the dispersing species in the donor ecosystem, or the probability that a dispersing individual reaches the recipient ecosystem. 3. We provide a review of pertinent literature demonstrating that these two mechanisms, and their chemical modulation, are well supported or likely to occur in many natural and human-modified landscapes. The literature also demonstrates that they can operate in concert with each other. 4. Synthesis and applications. Managed ecosystems thought to be important contaminant and nutrient sinks, such as artificial ponds and constructed wetlands, should be monitored and controlled for in-and-out animal movement if contaminant export is found to be relevant. Uncontaminated fishing grounds linked to contaminated sites via movement of dispersing species should be monitored and resident species evaluated for health consumption advisories. Assessing the success of contaminated site remediation can be improved by better matching the spatial extent of site remediation and the home range of monitored species. Finally, interagency research fund programmes should be developed that narrow the current gap between the fields of ecology and ecotoxicology.