Long-term exposure to microplastics and heat affects bumblebee behavior patterns, colony development and social networks

Pollinators are crucial for terrestrial ecosystems and global food security, but their populations are declining from multiple stressors including pollution and climate change. The effects of plastic pollution alone or in interaction with climate change on pollinators remain largely unexplored. Here, we investigate sublethal microplastic exposure effects on pollinators at individual, colony and network level in combination with heating to simulate climate warming. We conducted a one-generation trial on 30 bumblebee (Bombus terrestris) colonies in a customized beekeeping structure with a nesting and a foraging room, where colonies were maintained under optimal temperature (25 □) or heated condition (30 □), and fed with oil-seed rape pollens and 50% w/w sucrose solution containing 0, 10, or 100 mg/L 30 μm polyethylene beads. Real-time tracking with object detection (F1 = 83%) and matrix code scanning showed that microplastic exposure and heat significantly stimulated individual activity and altered labor division. Workers shifted to nursing behaviors and foraged more frequently for sucrose solution and less for pollen. Brood development was impaired by up to 48%, and colony population growth was restrained by 12–15%. Microplastic exposure and heating also significantly intensified social interactions and increased the dominance of the queen in her colony. These findings suggest that plastic pollution has complex, cross-level impacts on bumblebee colonies and their pollination potential, which may be exacerbated under climate change.