Micro- and nanoplastics effects in a multiple stressed marine environment

Micro- and nanoplastics (MNPs) pollution is an environmental issue of concern, but current effect assessments often overlook realistic scenarios, and a contextualised vision of the magnitude of the impact of complex mixtures of MNPs together with other environmental stressors is urgently needed. Plastic particles exist in the environment as complex mixtures of particles from various size ranges, shapes, and polymer types, but the potential effects of realistic MNPs mixtures and concentrations are still poorly understood, and current effects data is insufficient to produce high quality risk assessments. Organisms exposed to MNPs in the marine environment are simultaneously subjected to global change driven stressors, amongst others, such as ocean warming (OW), marine heat waves (MHW), ocean acidification (OA), and ocean deoxygenation (OD). Stress responses due to MNPs ingestion can, in particular cases, lead to a metabolic and energetic cost, which may be aggravated in the case of organisms already vulnerable due to simultaneous exposure to global change-related stressors. In this work, we discuss how MNPs effects could be assessed while considering plastics complexity and other environmental stressors. We identify knowledge gaps in MNPs assessments, acknowledge the importance of environmental data acquisition and availability for improved assessments, and consider how mechanistic ecological models can be used to unveil and to increase our understanding of MNPs effects on marine ecosystems. Understanding the importance of plastic pollution in the context of other stressors such as climate change and their potential combined effects on marine ecosystems is important. The assessment of realistic effects of MNPs on all biological levels of organisation should consider the co-occurrence in the environment of global change-related stressors. Even though the number of studies is still limited, recent effect assessment reports indicate that the MNPs interaction with global change stressors can affect processes in organisms such as ingestion and digestion, energy allocation, growth, and fecundity. The potential impact of this interaction at population levels is largely unknown and requires increased attention from the research community, to provide information to stakeholders on the vulnerability of marine species and ecosystems now and under future environmental conditions.