Effects of Microplastic Bioaccumulation in Freshwater Fishes on Environmental Sustainability: A Systematic Review of the Gangetic Basin
Dr. Sanjay Kumar
Abstract
The Ganga (Ganges) basin sustains one of the most densely populated riparian settlements globally and functions as a major conduit for land-derived plastic debris to the Bay of Bengal. Secondary fragmentation of mismanaged polymer waste generates microplastics (particles < 5 mm) that contaminate riverine surface waters, bed sediments, and ichthyofaunal tissues. This systematic review collates and harmonizes reported microplastic abundances across Gangetic abiotic matrices and native food fishes, rectifies prevailing taxonomic and unit-reporting inconsistencies, delineates physical, oxidative, endocrine, and vector-mediated toxicological pathways, and evaluates the operational capacity of rural statutory frameworks under Indian environmental rules. A structured literature retrieval across Scopus, Web of Science, ScienceDirect, PubMed, and Google Scholar yielded 35 primary peer-reviewed studies and three statutory instruments fulfilling strict quality and spectroscopic confirmation criteria. Reported microplastic abundances span 10²–10³ items m⁻³ in downstream reaches to 100–1550 particles L⁻¹ in upper Himalayan waters, while sediment burdens range from 17 to approximately 1300 items kg⁻¹ dry weight, reflecting methodological divergence in mesh apertures and digestion chemistries rather than a resolved natural gradient. Microplastics were found in all the fish groups studied along the basin with an average quantity ranging from 1 to 12 particles per fish, predominantly in Labeo rohita. Benthic and column-feeding guilds show reach-dependent ingestion patterns, which contradicts the hypothesis that demersal siluriforms consistently bear the highest burden. Microfibers are the most common fibers found in surface waters and include synthetic and semi-synthetic fibers. Crucially, visceral and branchial tissues exhibit an order-of-magnitude greater particle density than edible muscle tissue (0.054 vs. 0.005 items g⁻¹), highlighting culinary evisceration and degilling as the primary modifiable determinant of human dietary exposure. While the Gangetic basin has crossed the threshold of ubiquitous microplastic contamination across commercial fish species, direct socio-epidemiological links to clinical human morbidity remain a testable hypothesis requiring prospective cohort validation.