Long-term contamination of decabromodiphenyl ether reduces sediment multifunctionality: Insights from nutrient cycling, microbial ecological clusters, and microbial co-occurrence patterns.

Despite the widespread detection of polybrominated diphenyl ethers in aquatic ecosystems, their long-term effects on sediment multifunctionality remain unclear. Herein, a 360-day microcosm experiment was conducted to investigate how decabromodiphenyl ether (BDE-209) contamination at different levels (0.2, 2, and 20 mg/kg dry weight) affects sediment multifunctionality, focusing on carbon (C), nitrogen (N), phosphorus (P), and sulfur (S) cycling. Results showed that BDE-209 significantly increased sediment total organic carbon, nitrate, ammonium, available phosphorus, and sulfide concentrations, but decreased sulfate. Additionally, BDE-209 significantly altered key enzyme activities related to nutrient cycling. Bacterial community dissimilarity was positively correlated with nutrient variability. Long-term BDE-209 exposure inhibited C degradation, P transport and regulation, and most N metabolic pathways, but enhanced C fixation, methanogenesis, organic P mineralization, inorganic P solubilization, and dissimilatory sulfate reduction pathways. These changes were mainly regulated by microbial ecological clusters and keystone taxa. Overall, sediment multifunctionality declined under BDE-209 stress, primarily related to microbial co-occurrence network complexity and ecological cluster diversity. Interestingly, sediment C and N cycling had greater impacts on multifunctionality than P and S cycling. This study provides crucial insights into the key factors altering multifunctionality in contaminated sediments, which will aid pollution control and mitigation in aquatic ecosystems.