Abstract
This study investigated the environmental effects of two familiar emerging contaminants, sulfamethoxazole (SMX) and erythromycin (ERY), and their mixture (10:1 w/w) using a green microalga, R. subcapitata. The cell density, pigment content, and the activities of superoxide dismutase (SOD), catalase (CAT), glutathione (GSH) glutathione peroxidase (GSH-Px), and glutathione S-transferase (GST) were analyzed. The calculated EC50 values of SMX, ERY, and their mixture after 96 h were 0.49, 0.044, and 0.06 mg/L, respectively. High concentrations of antibiotics lead to a decrease in chlorophyll a and total carotenoid content, affecting the ability to photosynthesize ROS scavenging capacity. This may be a factor leading to the inhibition of algal growth. When R. subcapitata was exposed to SMX and the mixture, SOD and CAT increased to resist oxidative damage, while the activities of GSH and GST decreased, suggesting that this algae’s antioxidant system was unbalanced due to oxidative stress. R. subcapitata reduced the ERY-induced ROS by increasing the activities of SOD, GSH, and GST. The difference in the contents of nonenzymatic antioxidants and enzyme antioxidants in R. subcapitata indicated the antioxidant mechanisms to SMX and ERY were not identical. This study provides insights into the oxidative stress process in R. subcapitata under different antibiotics.
Highlights
Pharmaceuticals and personal care products (PPCPs) are over consumed daily and are transported to the aquatic environment
Microalgae have been recommended as a model organism for toxicity evaluation by the OECD [5]
The toxicity of SMX, ERY, and their mixture was investigated depending on the growth inhibition of R. subcapitata, which suggested that SMX was more toxic than ERY
Summary
Pharmaceuticals and personal care products (PPCPs) are over consumed daily and are transported to the aquatic environment. PPCPs are considered a type of emerging organic contaminant (EOC), which cover various groups of organic chemicals (such as antibiotics, hormones, and musk fragrances) and have received surprising concern in recent years. Antibiotics are released into the environment through several ways such as human excretion, improper disposal, and discharge from manufacturing sites and reach wastewater treatment plants (WWTPs). WWTPs are the predominant way of human pharmaceutical discharge into the aquatic environment [2]. Most antibiotics are not highly persistent, their consecutive production and discharge still lead to pseudo-persistent contamination and come into play through the interaction of specific pathways in target organisms at low concentrations [3,4]
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