Entangled stressors: a review on the interactions between microplastics and climate change in aquatic ecosystems

Microplastics (MPs) have become a cause for concern in aquatic ecosystems due to their potential to cause toxicity, which can be enhanced when co-occurring with other stressors. The contribution of climate change to MP toxicity mechanisms has been shown to be diverse, with more questions still remaining unanswered. Climate change influences the hydrologic dynamics of the aquatic environment through floods, which result in an increased abundance of MPs, whereas increased temperature in the aquatic ecosystem accelerates the leaching of additives from both macro and MPs. Moreover, increased metabolism as a result of increased temperature may also accelerate the uptake of MPs as they mistake them for food. While the combined effects of thermal stress and MP exposure pose serious threats to aquatic life, some organisms may exhibit resilience under certain conditions or adaptive mechanisms that could mitigate the impacts of MPs and associated contaminants. More studies are recommended to understand the long-term implications of these stressors in aquatic ecosystems and the potential for recovery after system restoration. Climate change and MP pollution are global phenomena; therefore, addressing their threats to aquatic ecosystems requires global collaborative efforts with regard to policy direction and the involvement of citizen science to integrate end-users in solution seeking. This review consolidates existing information on MP pollution and the role of climate change on the dynamics, fate, and toxicity effects of microplastics. Moreover, the review identifies some research gaps on the mechanisms driving their interactions, effect pathways in aquatic ecosystems, and the possible policy direction to enhance strategies to address this global threat.