Microplastic occurrence in fish species from the Iquitos region in Peru, western Amazonia

Abstract

The contamination of aquatic environments by microplastic has become a major threat to biodiversity. The presence of microplastic is documented in the aquatic fauna of the oceans, but, in the Amazon basin, reports on microplastic occurrence are few. The present study surveyed microplastic occurrence in fishes in an area of the Peruvian Amazon. We sampled 61 specimens of 15 commercial species from local markets in the city of Iquitos, Loreto Department. We detected a total of 2337 microplastic particles, 1096 in the gills and 1241 in the internal organs (esophagus, stomach, intestine, liver, gonads, pancreas, swim bladder and heart). The prevalence of microplastic particles was 100% and the overall average abundance was of 38.3 particles per individual (17.9 particles per individual in gills and 20.3 particles per individual in internal organs). Most particles were found in carnivorous fish. There was no correlation of particle abundance with fish standard length and weight. These results provided evidence of the degree of microplastic contamination of the fish fauna in the region of Iquitos.

Microplastics in the Amazon biome: State of the art and future priorities

“…Fibers predominated in both cases, comprising more than 80% of the MPs. However, only Chota-Macuyama and Mendoza [ 55 ] determined the polymeric composition of the particles, by digestion (NaOH 10 mol.L −1 for 120 h), which may account for the difference of one order of magnitude from the results of Rojas et al [ 54 ]. Additionally, Iquitos is a large urban center (146,853 inhabitants, 24.76 inhabitants.km −2 ) that continually suffers a process of unregulated urbanization, resulting in the rapid proliferation of periurban settlements exposed to poor sanitation conditions along the margins of the rivers that surround the city [ 75 , 76 ].…”

“… Purchased from local market Necropsy, digestion (10 Mol. L−1 NaOH, 120 h), sieving (0.075 μm mesh) Microscopy Cleaning of worksurfaces, blank control 38.3 MPs.individual −1 [ 54 ] S. aequifasciatus Experiment Lyophilization, digestion (HNO 3 , 70 °C, 2 h) Fluorescence spectroscopy – – [ 11 ] S. aequifasciatus Experiment – – – – [ 45 ] Sediment River sediment Van Veen grab Sieving (63 μm mesh), digestion (H 2 O 2 , room temperature, 24 h), flotation (1.70 kg.L −1 ZnCl 2 ), filtration (18 μm mesh) Microscopy Use of non-plastic instruments 417–8178 MP kg −1 [ 19 ] Beach sediment Hand trowel Sieving (2000 and 500 μm meshes) Microscopy Not described 987–761 MP kg −1 [ 44 ] Beach sediment Excavation of quadrants Sieving (250, 500 and 5000 μm meshes), flotation (1.15 kg.L −1 NaCl), filtration Microscopy Plastic cover on microscope, petri dishes to airborne contamination 492.5 MP m −3 [ 18 ] Beach sediment Excavation of quadrants Sieving (300 μm mesh),...…”

“…Fish have been collected by bottom trawls [ 17 , 49 ], hand nets [ 50 ], longlines and cast nets [ 51 ], or purchased from fishermen [ 52 , 53 ] or in local markets [ 54 , 55 ]. Invertebrates were collected manually by active searching [ 39 , 40 ].…”

“…Chota-Macuyama and Mendoza [ 55 ] found MPs in one out of 11 fish species, with a total frequency of occurrence of 12% and a mean abundance of 0.34 (±1.19) particles.individual −1 . One year later, Rojas et al [ 54 ] found MPs in 15 fish species from the same area, with items occurring in 100% of the specimens analyzed, in a mean abundance of 38.3 particles.individual −1 . Fibers predominated in both cases, comprising more than 80% of the MPs.…”

Fishes at Risk: Unveiling the Hidden Diversity of a Vulnerable Lake in the Peruvian Amazon Region

“…On the other hand, pollution from microplastics is another serious issue that has been escalating in recent years (Rojas et al, 2023). Studies have shown that the presence of microplastics in the stomachs of fish has significantly increased from the mid-century to the present, correlating with the rise in plastic concentration in the environment (Hou et al, 2021).…”