Anionic surfactants (ASs), represented by linear alkylbenzene sulfonate (LAS), are compounds that can change the interfacial tension of target solutions. They are widely used in various industrial fields such as metal processing, petroleum and petrochemicals.

LAS is a common organic pollutant that play an important regulatory role in the succession of algal communities. Previous studies have found that LAS promoted the growth of Microcystis at low concentrations (≤ 10 mg/L) while inhibiting growth at high concentrations (≥ 20 mg/L). However, there are few reports referring to the distribution pattern of LAS in water bodies and its potential impact on the interspecies competition of Microcystis communities and the comprehensive toxicity of blooms.

Recently, a research group led by Prof. LI Dunhai from the Institute of Hydrobiology (IHB) of the Chinese Academy of Sciences elucidated the regulatory effects, regulatory thresholds, and biological mechanisms of environmental concentrations of LAS on Microcystis bloom toxicity from the perspectives of photosynthesis, population competition, and microcystin (MCs) synthesis. This study was published in Water Research.

The researchers conducted field investigations in Lake Taihu, and they found that the concentration of AS (mainly LAS) in the water surface microlayer (SML) reached 580 μg/L, higher than that in the lower layer.

Since floating Microcystis blooms overlap in space with the high concentration of AS in SML, the researchers speculated that the impact of LAS on Microcystis blooms may have been severely underestimated in previous studies. They found that the regulatory effect of LAS on Microcystis bloom toxicity under suitable simulated growth conditions can be divided into four pathways according to the mechanism and threshold.    

In terms of mechanism, compared with nontoxic Microcystis, toxic Microcystis can better resist LAS stress by dissipating excess light, maintaining an intact membrane structure and maintaining cellular homeostasis. Transcriptome sequencing suggested that the photosynthetic damage of nontoxic Microcystis might be attributed to the impacts of LAS on the absorption and assimilation of nitrogen, which finally resulted in the degradation of phycobilisomes.

This study revealed the ecological significance of anionic surfactants, providing new insights for the establishment of wastewater discharge standards and water quality safety management.