Occurrence and variability of microplastics in immature aquatic insects of freshwater streams in Kelantan

Microplastics (MPs) contamination has been discovered in aquatic ecosystems worldwide. However, studies on MPs accumulation in living entities, notably immature aquatic insects, which are a crucial food source for other aquatic organisms, are still lacking. Therefore, this study aims to determine the presence of MPs in immature aquatic insects, specifically Ephemeroptera (mayflies), Plecoptera (stoneflies), and Trichoptera (caddisflies). These immature aquatic insects were sampled from two tributaries of Gua Musang in Kelantan: the Lebir stream and the Nenggiri stream. A stereomicroscope was used to identify the species of the collected samples, while Micro-Fourier-Transform Infrared (μFTIR) spectroscopy was employed for the physical identification and chemical analysis of MPs. The Lebir stream contained 14 types of MPs, whereas the Nenggiri stream contained 10 types of MPs, with an average abundance per individual of 21.45% and 25.12%, respectively. The most common MP polymer was cellulose nitrate (12.4%), followed by poly (2,2,2-trifluoroethyl vinyl ether), and polyethylene glycol 200 dibenzoate. The study also found a positive correlation between the functional feeding groups of the immature aquatic insects and MPs abundance in both streams, where the collector-gatherers ingested most of the food sources in the ecosystem, thereby increasing MPs accumulation. The finding suggests that MPs contamination in the tributaries of Gua Musang is reflected in the presence of MPs in these streams and the immature aquatic insects. MPs pollutants can impact freshwater ecosystems, particularly immature aquatic insects, by reducing their growth, lowering fertility rates and altering their feeding habits. In addition, exposure to MPs can have adverse effects on higher trophic level consumers, including humans who may experience respiratory discomfort, cytotoxic effects, inflammatory responses and autoimmune diseases.