Evaluation of Toxicological Risks and Effects of Microplastics on Nile Tilapia (Oreochromis niloticus) under in Vitro Laboratory Conditions

Abstract

Microplastics have been reported by many literatures as contaminants of environmental water bodies and are ingested by aquatic organisms due to their small sizes. Knowing the effects of microplastics to freshwater fish that are kept in ponds helps in managing fish-keeping practices. The objective of the research was to determine the toxicity of microplastics to Nile tilapia (Oreochromis niloticus). The Experiment was done in 80 fish samples. Microplastics that were prepared for the batch experiment were introduced in the aquarium followed with observation for 21 days. The digestion of fish gills and intestines involved 10 mL of 10% (w/v) KOH solution and incubation at 65^oC for 24 hours. Engulfed microplastics were determined using a stereo microscope and At-IR spectrophotometer for confirmation. Engulfed microplastics were observed to be in the mean range of 3.37 x 10²±4.04 x 10² to 2.32 x 10³ ± 3.57 x 10³ particles/kg in gills and 4.68 x 10⁴ ± 3.02 x 10⁴ to4.40 x 10⁴ ± 5.34 x 10⁴ particles/kg in intestines. The observed responses were loss of equilibrium for 35% of fish, abnormal swimming for 49% of fish, abnormal ventilator behavior for 59% of fish, abnormal appearance for 39% of fish and average growth weight increase in control experiment fish was 6.10±2.62 g compared to 1.7 ± 3.62 g in test fish. There was no mortality of Nile tilapia. The responses of fish to the presence of microplastics in aquariums indicated that microplastics had adverse effects to Nile tilapia (Oreochromis niloticus). More researches have to be done on fish physiological changes caused by microplastics.