Bacterial Production Modulates the Persistence of Organophosphate Ester Flame Retardants and Plasticizers in the Ocean

Understanding the biodegradation of organic pollutants is crucial for assessing the persistence and fate of these contaminants and improve their risk assessment, eventually drawing policy. The occurrence of organophosphate ester (OPE) flame retardants and plasticizers has been widely reported in the marine environment. However, few studies have assessed the potential of marine microorganisms to degrade them, particularly under oceanic conditions. Here, we report the results of six degradation experiments where in situ bacterial communities were challenged with environmentally relevant concentrations of OPEs in the Atlantic and Southern Oceans. Hydrophobic aryl-OPEs significantly decreased by 60% and 25% in the Atlantic and Southern Oceans, respectively. In Atlantic waters, up to 40% of OPE depletion was due to sorption to cells and close to 20% to biodegradation. The cold temperatures of the Southern Ocean resulted in a slower, nondetectable biodegradation, further confirmed by bacterial production results. Bacterial composition exposed to OPEs also showed a larger degree of changes in the Atlantic than in the Southern Ocean. Significant negative correlations were found between the fold changes in bacterial production and the decreases in OPE concentrations, suggesting that bacterial carbon demand is directly related to OPE biodegradation in the oceans.