The effects of Cefixime and Aspirin on phytoplankton community structure and dynamics: A Mesocosm approach

Pharmaceuticals are emerging contaminants of interest due to their ability to induce changes in the environment. These chemical compounds are discharged into aquatic ecosystems with a high likelihood of affecting non-target organisms such as phytoplankton. However, there is a gap in knowledge regarding the effects of pharmaceuticals on phytoplankton. This study used the mesocosm approach to investigate the effects of cefixime, a cephalosporin antibiotic and aspirin, a nonsteroidal anti-inflammatory drug on the community structure (species diversity, richness, and abundance) of phytoplankton. The mesocosm approach studied the effects of three treatments of pharmaceuticals: cefixime, aspirin and a combination of cefixime and aspirin, alongside a control experiment for 21 days. A total of 31 phytoplankton species belonging to five groups were identified; with diatoms and green algae having higher diversity compared to the other algae groups. Scenedesmus sp., Pediastrum sp. and Zygnema sp. were the top three recurring species in all the samples taken throughout the experimental period. Navicula sp. were the most recurring diatoms. The exposure of phytoplankton to cefixime, aspirin, and a combination of cefixime and aspirin significantly reduced the diversity, richness, and abundance of all species by the 21st day of the experiment. The control had the highest cell density (8,910 cells mL) of phytoplankton species on the 21st day, while the cefixime treatment had the lowest cell density (48 cells mL) f phytoplankton species on the seventh day of the study. This study demonstrated that cefixime and aspirin had major impacts on the phytoplankton community.