An new study led by the Wuhan Botanical Garden of the Chinese Academy of Sciences has revealed that the combined presence of heavy metals and antibiotics in the aquatic environment poses a serious threat to essential nitrogen transformation processes and overall multifunctionalityin constructed wetlands (CWs).

Over 84 days, researchers systematically investigated the combined effects of copper(Cu) and three antibiotics- sulfamethoxazole (SMZ), doxycycline (DC), and ciprofloxacin (CIP) - on wetland ecosystems. 

This study demonstrated that high Cu levels, particularly in conjunction with SMZ,  inhibited denitrification and anammox, but increased N₂O emissions. Under equivalent concentration antibiotics stress, adding high Cu levels triggered a microbial community shift characterized by reduced diversity, and an enriched abundance of dominant phyla (e.g., Proteobacteria). Microbial co-occurrence networks were more substantially influenced by DC and CIP than SMZ. Antioxidant enzyme activities and malondialdehyde levels exhibited pollutant specific responses, varying with both Cu dosage and antibiotic type. A low Cu dose enhanced wetland ecosystem multifunctionality, but this benefit was reversed under high copper stress, particularly when combined with the antibiotic DC.

These findings highlight that the persistent co-accumulation of heavy metals and antibiotics can simultaneously alter the structure, ecological processes, and multifunctionality of wetland ecosystems, and underscore that these impacts is directly linked to Cu concentration and antibiotic types. 

This research was supported by the National Natural Science Foundation of China and Hubei Provincial Key Research and Development Program. Associate professor MA Lin and YU Desheng are co-first authors, and associate professor MA Lin, Professor LIU Wenzhi, and Dr. HE Gang are co-corresponding authors. 

The relevant research results have been published in Journal of Environmental Management entitled "Combined stressors of copper and antibiotics alter nitrogen transformation and multifunctionality of constructed wetlands: Responses of microbes and macrophytes".

A diagram illustrating the pathway by which combined pollutants alter nitrogen transformation and multifunctionality in wetlands (Image by MA Lin)