Microplastics and Copper Affect Zebrafish Behavior and Responses to Predation Threat.

Area of Science:

• Environmental Toxicology
• Aquatic Toxicology
• Ecotoxicology

Background:

• Microplastics are ubiquitous environmental pollutants with poorly understood toxicological impacts.
• Copper is a metal pollutant known to affect fish olfaction and behavior.
• Interactions between microplastics and metals may alter toxicological outcomes.

Purpose of the Study:

• To investigate the effects of polyethylene microplastics of two size classes on zebrafish behavior.
• To assess the combined effects of microplastics and copper on zebrafish behavior, bioaccumulation, and metallothionein induction.
• To understand how microplastics and copper influence zebrafish responses to a conspecific alarm cue.

Main Methods:

• Zebrafish were exposed to two sizes of aged polyethylene microplastics (small: 13.2 µm, large: 595.7 µm) with or without copper (10 μg/L).
• Behavioral responses, including swimming speed and reaction to an alarm cue, were monitored.
• Copper bioaccumulation and metallothionein (a biomarker for metal exposure) levels were measured.

Main Results:

• Microplastic exposure decreased zebrafish swimming speed.
• Combined exposure to copper and microplastics resulted in higher swimming velocities than copper alone, but large microplastics increased copper bioaccumulation and metallothionein production.
• Small microplastics and copper exposure significantly altered behavioral responses to an alarm cue, forming a distinct group in multivariate analysis.

Conclusions:

• Microplastics exhibit complex interactions with copper, influencing zebrafish behavior and physiology.
• The presence of microplastics can modify the toxic effects of copper, sometimes exacerbating bioaccumulation and biomarker responses.
• Comprehensive risk assessments are crucial to understand the multifaceted impacts of microplastics and co-pollutants in aquatic environments.