Multiple Stressor Effects of a Neonicotinoid, Heatwaves, and Elevated Temperatures on Aquatic Insect Emergence

Area of Science:

• Ecology
• Environmental Science
• Insect Biology

Background:

• Intensive agriculture, particularly neonicotinoid insecticides, and climate change are implicated in global insect decline.
• Ecologically realistic field experiments on multiple stressors affecting aquatic insects are limited.

Purpose of the Study:

• To investigate the effects of imidacloprid and climate change scenarios (elevated temperatures and heatwaves) on aquatic insect emergence.
• To assess the combined impacts of these stressors on insect biomass, abundance, and community structure.

Main Methods:

• An outdoor mesocosm study was conducted over three months.
• Aquatic insect communities were exposed to single and combined stressors: imidacloprid (1 and 10 μg/L), elevated temperatures (+4 °C), and recurring heatwaves (+0 to 8 °C).
• Insect emergence was monitored throughout the experiment.

Main Results:

• Significant losses in insect biomass and abundance were observed under both single and combined stressor treatments.
• A high imidacloprid concentration combined with elevated temperatures caused a 47% decline in total insect biomass.
• Diptera and Ephemeroptera were the most sensitive insect orders, with Diptera abundance significantly reduced by the combination of high imidacloprid and heatwaves.

Conclusions:

• The study demonstrates that combined agricultural and climate stressors significantly threaten aquatic insect communities.
• Temperature-enhanced imidacloprid toxicity is a critical factor driving insect decline.
• Effective climate change mitigation strategies are crucial for conserving aquatic insect biodiversity.