Microbial aspects of linear alkylbenzene sulfonate degradation in coastal water

Viable and total bacteria were determined during linear alkylbenzene sulfon ate (LAS) degradation in coastal seawater. Viable bacteria were determined by plate counts on marine agar media, while total bacteria were determined by flow cytometry after SYTO-13 staining. LAS degradation was monitored by high-performance liquid chromatography analysis. Seawater samples with LAS at 5 mg/L, incubated in the laboratory (20 degrees C, 100 rpm, 30 d), showe d in most cases a similar evolution in bacterioplankton abundance over time , characterized by three phases: (i) a progressive increase in bacterial de nsity; (ii) a later decrease; and (iii) a fluctuating stationary phase. Bac terioplankton degraded the LAS by growing to populations with a high percen tage of viable bacteria. The bacteria were rapidly grazed by protozoa, prev enting anomalous high bacterial growth and ensuring the later channeling of LAS carbon to upper trophic levels.