Use of a flow-through in situ environmental chamber to study microbial adaptation processes in riverine sediments and periphyton

Abstract

Adaptation of sediment-associated and periphytic microbial communities to the quaternary ammonium surfactant dodecyltrimethylammonium chloride (C12-TMAC) was assessed using an in situ environmental chamber. The chamber was placed on the bottom of the Little Miami River (Ohio) and consisted of six channels that were aligned so the river water flowed through them. Concentrated C12-TMAC was dosed to the channels to achieve nominal concentrations of 0 (control), 0.25 and 25 mg/L. Periodically, samples of sediment and periphyton were removed and the biodegradation of C12-TMAC was measured. Results demonstrated that the in situ system was a useful method for assessing the impact of chemicals on aquatic microbial communities. Adaptation to C12-TMAC occurred in both sedimentary and periphytic compartments within 5 to 10 d of exposure. Both biodegradation potential (Vmax) and first-order biodegradation rate constants (K1) increased 15- to 60-fold relative to activity in the control channel. Adaptation was accompanied by an increase in the most-probable number (MPN) of C12-TMAC degraders. However, the increase in MPN was not directly proportional to the increase in biodegradation activity. Results from this work were comparable to previous research using laboratory microcosms, indicating that such laboratory systems are comparatively accurate models of field-measured adaptation responses.