A freshwater food web model for the combined effects of nutrients and insecticide stress and subsequent recovery

Abstract

A microcosm experiment that addressed the interaction between eutrophication processes and contaminants was analyzed using a food web model. Both direct and indirect effects of nutrient additions and a single insecticide application (chlorpyrifos) on biomass dynamics and recovery of functional groups were modeled. Direct toxicant effects on sensitive arthropods could be predicted reasonably well using concentration-response relationships from the laboratory with representative species. Model predictions showed that nutrient additions alone caused only small effects on toxicant fate and effects probably due to the relatively high dissipation rate of chlorpyrifos. Enhancement of eutrophication effects by the insecticide was relatively small and seemed to be additive. The recovery of some affected functional groups was hampered in the indoor microcosms due to their isolation from outdoor seed populations. Introducing recolonization scenarios in the model simulated dose-dependent recovery. Recolonization increased the recovering rate after exposure to the pesticide. Modeling can extend the use of microcosms as a link between laboratory and field as this allows the prediction of effects and recovery of ecosystems for concentrations that have not been experimentally tested.

Comparison of environmental risks of pesticides between tropical and nontropical regions

“…After all, toxic effects on aquatic organisms depend not only on the concentration of the toxicant but also on the duration of exposure. Consequently, any adverse effect will be of short duration in the tropics and, therefore, the recovery of individuals and populations of small aquatic organisms will be enhanced as well (Van den Brink et al 2002;Traas et al 2004).…”

Environmental Risk Assessment of Agrochemicals — A Critical Appraisal of Current Approaches

“…Also, organisms are usually confined to the small experimental area (a few square metres per unit) and thus can be counted more reliably. Indirect effects on other species and communities are usually detected in this kind of experiments [134,135], whereas such effects would be difficult to observe and measure in field trials. One positive feature of mesocosms and microcosms is that they avoid contamination of the environment, something that field trials cannot do.…”

Traits‐based approaches in bioassessment and ecological risk assessment: Strengths, weaknesses, opportunities and threats

“…They are, therefore, often used to test hypotheses on cause and effects of stressors at the community or ecosystem level in relation to recovery (see, e.g., Brock et al 2009) and indirect effects (Fleeger et al 2003). The mechanistic knowledge derived from these semifield experiments can be used to develop mechanistic effect models to support the ERA of chemicals (examples include Traas et al 2004 andVan den Brink et al 2007). Hommen et al (2010) defined five areas of application of mechanistic effects models in ERA, 1) extrapolation of organism-level effects to the population level, 2) extrapolation of effects between different exposure patterns, 3) extrapolation of recovery processes, 4) analysis and prediction of indirect effects in communities, and 5) prediction of bioaccumulation within food chains or food webs.…”