Effects of Microplastics on Aquatic Biota: Exposure Pathways, Toxic Mechanisms, and Ecosystem-Level Consequences

Abstract

Microplast.ics and nanoplastics have emerged as pervasive aquatic contaminants of growing academic and societal concern, reflecting modern plastic-dependent lifestyles and intensifying pressures on freshwater and coastal ecosystems. Their persistence, fragmentation into highly bioavailable size fractions, and capacity to interact with chemical co-contaminants have heightened attention to ecological and food-security risks, particularly in regions experiencing rapid urbanization and uneven waste-management capacity. This review aims to synthesize recent evidence on how microplastics move through aquatic environments, the pathways by which aquatic biota are exposed, the toxic mechanisms driving biological harm, and the ecosystem-level consequences that may result from chronic contamination. A PRISMA-guided systematic literature review was conducted, integrating peer-reviewed studies and authoritative reports published between 2021 and 2025 through qualitative synthesis of field observations, mechanistic research, and monitoring frameworks. The paper consolidates knowledge across four core areas: sources and transport processes across water columns and sediments; exposure pathways including ingestion, gill contact, and trophic transfer; organism-level toxicity encompassing physical stress, oxidative imbalance, inflammation, organ dysfunction, and reproductive and behavioural disruptions; and ecosystem-scale outcomes affecting food webs, productivity, biodiversity, and ecosystem services such as fisheries. Across the reviewed literature, consistent patterns indicate that sediments function as long-term sinks, biological exposure is strongly structured by feeding ecology and habitat use, and multi-stressor interactions may intensify adverse outcomes beyond particle effects alone. The review underscores the need for standardized monitoring, nanoplastic-sensitive analytics, long-term chronic exposure studies, and upstream interventions targeting plastic leakage. These insights support evidence-based policy and management strategies to protect aquatic health and sustain ecosystem services.