Influence of the antibiotic nitrofurazone on community dynamics of marine periphytic ciliates: Evidence from community-based bioassays

Marine periphytic ciliates play a pivotal role in shaping coastal ecosystems dynamics, thereby acting as robust biological indicators of aquatic ecosystem health and functionality. However, the understanding of the effects of veterinary antibiotics on composition and structure of periphytic ciliate communities remains limited. Therefore, this research investigates the influence of the veterinary antibiotic nitrofurazone on the community dynamics of marine periphytic ciliates through bioassay experiments conducted over a one-year cycle. Various concentrations of nitrofurazone were administered to the tested ciliate assemblages, and subsequent changes in community composition, abundance, and diversity were quantitatively analyzed. The research revealed significant alterations in periphytic ciliate communities following exposure to nitrofurazone. Concentration-dependent (0–8 mg L⁻¹) decrease in ciliates abundance, accompanied by shifts in species composition, community structure, and community patterns were observed. Comprehensive assessment of diversity metrics indicated significant changes in species richness and evenness in the presence of nitrofurazone, potentially disrupting the stability of ciliate communities. Furthermore, nitrofurazone significantly influenced the community structure of ciliates in all seasons (winter: R² = 0.489; spring: R² = 0.666; summer: R² = 0.700, autumn: R² = 0.450), with high toxic potential in treatments 4 and 8 mg L⁻¹. Differential abundances of ciliates varied across seasons and nitrofurazone treatments, some orders like Pleurostomatida were consistently affected, while others (i.e., Strombidida and Philasterida) showed irregular distributions or were evenly affected (e.g., Urostylida and Synhymeniida). Retrieved contrasting patterns between nitrofurazone and community responses underscore the broad response repertoire exhibited by ciliates to antibiotic exposure, suggesting potential cascading effects on associated ecological processes in the periphyton community. These findings significantly enhance the understanding of the ecological impacts of nitrofurazone on marine periphytic ciliate communities, emphasizing the imperative for vigilant monitoring and regulation of veterinary antibiotics to protect marine ecosystem health and biodiversity. Further research is required to explore the long-term effects of nitrofurazone exposure and evaluate potential strategies to reduce the ecological repercussions of antibiotics in aquatic environments, with a particular focus on nitrofurazone.