Structural changes in a macrozoobenthos assemblage after imidacloprid pulses in aquatic field-based microcosms.

Area of Science:

• Ecotoxicology
• Aquatic Ecology
• Environmental Science

Background:

• Neonicotinoid insecticides, like imidacloprid, are widely used and can enter aquatic ecosystems.
• Understanding the impact of pulsed pesticide exposure on aquatic invertebrates is crucial for ecological risk assessment.
• Field-based microcosm experiments offer a controlled yet naturalistic approach to study these effects.

Purpose of the Study:

• To investigate the effects of repeated imidacloprid pulses on a lentic macrozoobenthos assemblage.
• To assess the ecological impact under natural conditions, considering organism interactions.
• To evaluate the efficacy of a field microcosm approach for pesticide impact studies.

Main Methods:

• A field-based microcosm experiment was conducted using a lentic benthos assemblage.
• Organisms were exposed to three imidacloprid pulses weekly at concentrations from 0.6 to 40 μg/L.
• Imidacloprid photodegradation was monitored, with a half-life of 28 ± 8 hours.

Main Results:

• Decreased abundance and emergence of Ephemeroptera were observed.
• Reduced survival rates in chironomid species (Tanypodinae, Orthocladiinae) occurred at 2.3 μg/L.
• The gastropod Radix sp. became dominant at higher imidacloprid concentrations due to reduced competition.

Conclusions:

• Repeated short-term imidacloprid contamination can impact aquatic ecosystems, even with rapid photodegradation.
• Pulsed low-level insecticide exposure can alter community structure and species dominance.
• Field microcosms are effective tools for assessing the ecological effects of contaminants like imidacloprid.