Invasive Species Mediate Insecticide Effects on Community and Ecosystem Functioning.

Area of Science:

• Ecotoxicology
• Freshwater Ecology
• Invasive Species Biology

Background:

• Anthropogenic activities introduce pesticides and invasive species into freshwater ecosystems, complicating ecological risk assessment.
• Combined stressors can alter community structure and ecosystem functioning, but their interactions are not fully understood.

Purpose of the Study:

• To investigate the direct and indirect effects of chlorantraniliprole (CAP) on benthic macroinvertebrate communities and ecosystem functions.
• To assess how invasive crayfish and invasive Eucalyptus globulus leaf litter mediate insecticide toxicity and impact freshwater ecosystems.

Main Methods:

• Artificial stream mesocosms were used to test the effects of chlorantraniliprole (CAP) exposure.
• The study examined the influence of invasive crayfish (Procambarus clarkii) and invasive Eucalyptus globulus detritus on macroinvertebrate community structure and ecosystem functions (leaf decomposition, primary production).
• Structural equation modeling (SEM) was employed to analyze the interactions between stressors and their effects.

Main Results:

• Low CAP concentrations reduced shredder and grazer abundance, decreasing leaf decomposition and increasing primary production.
• Invasive species (crayfish and E. globulus litter) reduced macroinvertebrate survival, leaf decomposition, and enhanced primary production.
• SEM revealed that crayfish presence or E. globulus litter mediated CAP toxicity to macroinvertebrates.

Conclusions:

• Invasive species alter the impact of insecticide exposure on benthic freshwater communities.
• The study provides a mechanistic understanding of indirect effects and interactions of multiple stressors on ecosystem functions.
• Integrating biotic stressors into ecotoxicological experiments is crucial for accurate risk assessment.