Enhanced tolerance of salt-adapted <i>phragmites australis</i> to antibiotic-induced oxidative stress

Intensive aquaculture heavily relies on antibiotics to prevent and treat fish diseases, raising concerns about antibiotic resistance, environmental contamination, and human health impacts. This study evaluated the growth, physiological responses, elemental content, oxytetracycline (OTC), and nitrogen removal performance of Common Reed (<i>Phragmites australis</i>) in fresh and mesohaline antibiotic-spiked solutions over 36 days. Eight treatments (0, 0.01, 0.1, 1 mg/L OTC) in freshwater and mesohaline conditions were tested, with controls included. Positive combined effects were observed in leaf temperature, photosynthetic performance, and root P content, while negative effects were found in root Fe content. OTC did not affect N content, C content, C/N ratios, plant height, or chlorophyll content. In non-saline conditions, nitrate removal reached 81–92%, regardless of OTC concentration, but was reduced by 43% due to salinity. Phytoremediation was responsible for 5–70% nitrate, 99% ammonium, and up to 14.6% OTC removal. These findings suggest <i>P. australis</i> is well-suited for bioremediation of nitrate and ammonium in non-saline constructed wetlands, despite OTC presence. However, its nitrate removal capacity is hindered by salinity, making it more effective in non-saline environments. These results highlight the potential of <i>P. australis</i> as an efficient biological method to decrease contaminants in non-saline environments. The results of this study expand on the knowledge that <i>P. australis</i> can uptake OTC from spiked growth mediums (Carvalho <i>et al</i>. 2012; Liu <i>et al</i>. 2013) by testing this species’ ability to bioremediate OTC, nitrate and ammonium under the salinity in which antibiotic-contaminated wastewaters of shrimp aquaculture are commonly found. It additionally analyzes the single or combined effects of salinity and OTC on Common Reed’s physiology, to understand the underlying processes controlling this response.