Microbial aspects of linear alkylbenzene sulfonate degradation in coastal water

Viable and total bacteria were determined during linear alkylbenzene sulfonate (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), showed in most cases a similar evolution in bacterioplankton abundance over time, characterized by three phases: (i) a progressive increase in bacterial density; (ii) a later decrease; and (iii) a fluctuating stationary phase. Bacterioplankton degraded the LAS by growing to populations with a high percentage of viable bacteria. The bacteria were rapidly grazed by protozoa, preventing anomalous high bacterial growth and ensuring the later channeling of LAS carbon to upper trophic levels.