Environmental assessment of antibiotic toxicity under climate change-related temperature and pH scenarios using Danio rerio.

Climate change induced temperature and pH shifts can alter aquatic environments, potentially intensifying antibiotic toxicity, disrupting the physiological balance of aquatic organisms. Few studies have examined combined effects of these abiotic environmental stressors and antibiotics on aquatic ecosystems in a potential climate change scenario. This study evaluated the toxicity of environmentally relevant concentrations of sulfamethoxazole (150 µg SMX/L), trimethoprim (30 µg TRIM/L), and their mixture (MIX: 150 µg SMX/L + 30 μg TRIM/L) in Danio rerio under two scenarios: standard (26 °C, pH 7.5) and climate changed (28 °C, pH 9.0). A multi-biomarker approach was performed to evaluate oxidative stress, lipid peroxidation, neurotransmission, energy metabolism, and DNA damage. Integrative assessment of an organism's health showed that increasing pH and temperature intensified SMX and TRIM toxicity, shifting from marginally to highly toxic. Meanwhile, MIX toxicity increased from marginally to moderately toxic. Under standard conditions, SMX and TRIM caused major alterations (affecting antioxidant/detoxification mechanisms), while MIX induced severe alterations in D. rerio's health status. Under a climate-changed scenario, all antibiotics led to severe alterations (lipid peroxidation, DNA damage, and energy metabolism disruption). These findings suggest that under a climate-changed scenario (higher temperature and pH increase), both individually and in mixtures, antibiotic toxicity leads to more severe effects on D. rerio. Given this, it is crucial to consider environmental factors when assessing antibiotic toxicity, as shifts in temperature and pH can significantly amplify their harmful effects. Understanding these interactions is essential for developing effective regulatory and conservation strategies to safeguard aquatic ecosystems from long-term ecological imbalances.