Effect of Linear Alkylbenzene Sulfonate on the Structure and Function of Microbial Communities in Model Ecosystems

Abstract

The effect of linear alkylbenzene sulfonate (LAS) on the structure and function of microbial communities was studied in a flow-through model ecosystem containing several trophic levels. The LAS was supplied to 19-litre glass aquaria at 0.5 and 5.0 mg/litre in either well water (Phase I) or sewage effluent (Phase II). The structure of microbial populations was estimated from measurements of total viable biomass; function assays consisted of measuring rates of glucose or LAS degradation, or both. Assays of microbial function were also carried out in waters from two rivers. The results of Phase I studies indicated that LAS had no effect on microbial structure at either dose level. Microbial function was also unaffected at the low-dose level, although both glucose and LAS degradation were inhibited at the high-dose level. By contrast, 5 mg/litre LAS had no effect on microbial function in river water exposed to sewage effluent, as measured by the rate of LAS degradation. Similarly, there was no decrease in function of the microbial populations exposed to ∼5 mg/litre LAS in the Phase II model ecosystem. It was further noted that the overall kinetics of LAS degradation in Phase II model ecosystems were essentially identical to those in two river waters. From Phase I and Phase II studies the following were concluded: 1. Function measurements were preferable to structure measurements in characterizing mixed microbial communities. 2. The function of microbial communities in relatively simple model ecosystems closely approximates that of natural populations in surface waters.