Increase in temperature increases ingestion and toxicity of polyamide microplastics in Nile tilapia

Abstract

Microplastics (MP) pollution and global warming are worldwide concerns, creating various physiological problems for aquatic organisms. This study was carried out to know the effects of different temperature (30, 33 and 36 °C) on ingestion of MP along with the physiological consequences in Nile tilapia (Oreochromis niloticus) exposed to virgin polyamide (PA) (10 mg/L water; 500 μm to 4 mm in size) for 15 days. A significant difference was found in PA ingestion of the fish treated with different temperature. Fish from 36 °C temperature groups ingested highest amount of PA (136 ± 24.40 item/fish) during the exposure period. The hemoglobin (Hb) and red blood cell (RBC) decreased significantly in the highest temperature (36 °C) without PA exposure. At the same time, Hb increased, but RBC significantly reduced in all the temperature conditions with PA exposure. The number of white blood cell (WBC) and glucose level increased significantly in the highest temperature (36 °C) without PA exposure. In contrast, WBC increased and glucose decreased significantly in all the temperature conditions with PA exposure. Frequencies of various nuclear and cellular abnormalities of erythrocytes increased significantly in the fish exposed to all temperature with PA exposure, though severity increased with temperature. Similarly, histological damage of gills (hyperplasia, epithelial necrosis, deformed pillar system, epithelial lifting, telangiectasia) and intestine (epithelium breakage, enterocyte vacuolization and shortening of villi) was found to be mild to severe by the accumulation of PA, increased severity with increase of temperature. This study confirms that global warming as a consequence of climate change might influence MP ingestion hampering physiological state of fish.