The Invisible Threat: A Review of Microplastics in Freshwater Systems, Including Their Presence in Water, Sediment, and Aquatic Insects

Plastic particles, often referred to as microplastics, are less than 5 mm in diameter, and have become an inescapable and highly pervasive threat across freshwater environments. Their occurrence in the water, sediments and biological structures in water are a major ecological and biological concern. The current review has conducted a systematic analysis of their sources, spatial distributions, and effects on environment considering especially their occurrence in the water bodies, sediments, and aquatic invertebrates. Routes of entry are urban runoff, wastewater effluent, and agricultural operations and the review discusses the effect of the characteristics of particles on the environment and bioavailability. Considering their importance in food webs and ecosystem activity, aquatic insects are getting more recognition to detect microplastic pollution as bioindicators, which is due to their tendency to ingest and accumulate particles. Existing methods of detection are discussed, as well as limitations in the methods of such a study that cannot make results comparable in different studies. There are also noted gaps in knowledge, the lack of sufficient research in low- and middle-income countries and the need to develop standardized monitoring procedures. To understand the fate and effect of microplastic in freshwater compartments leading to the implementation of effective management strategies is important. Therefore, the review highlights the need for integrated scientific and policy programs aimed at reducing microplastic pollution and maintaining freshwater biodiversity.