Risk assessment of oxytetracycline in water phase to major sediment bacterial community: A water-sediment microcosm study

With an increasing need for assessing the risk of aquaculture antibiotics, there has been growing interest in their fate and effect on sedimentary bacteria. Here we show the risk assessment for oxytetracycline (OTC) use in seawater and its subsequent transfer to sediment, and illustrate that the sediment bacterial community was stable against OTC at dosed concentrations. Water-sediment microcosm experiments were conducted to simulate quiescent aquaculture conditions. The sorption coefficient (Kd) was 12.3-44.2 mL/g, which is lower than the previous reports employing vigorous mixing. In a denaturing gradient gel electrophoresis (DGGE) analysis, the addition of OTC at 50 μg/L into the water phase had little effect on the major sediment bacterial community structure. This finding suggests that low concentrations of OTC in the water phase - such as those used within many aquaculture operations - do not pose a high risk of causing major changes in environmental sediment bacterial community structures.