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Sorption-desorption kinetics and toxic cell concentration in marine phytoplankton microalgae exposed to Linear Alkylbenzene Sulfonate

Abstract:

Linear Alkylbenzene Sulfonates (LAS) are ubiquitous surfactants. Traces can be found in coastal environments. Sorption and toxicity of C12-LAS congeners were studied in controlled conditions (2-3500μg C12LAS/L) in five marine phytoplanktonic species, using standardized methods. IC50 values ranged from 0.5 to 2mg LAS/L. Sorption of 14C12-6 LAS isomer was measured at environmentally relevant trace levels (4μg/L) using liquid scintillation counting. Steady-state sorption on algae was reached within 5h in the order dinoflagellate>diatoms>green algae. The sorption data, fitted a L-type Freundlich isotherm, indicating saturation. Desorption was rapid but a low LAS fraction was still sorbed after 24h. Toxic cell concentration was 0.38±0.09mg/g for the studied species. LAS toxicity results from sorption on biological membranes leading to non-specific disturbance of algal growth. Results indicate that LAS concentrations in coastal environments do not represent a risk for these organisms. © 2011 Elsevier Ltd.