Sodium chloride incites reactive oxygen species in green algae Chlorococcum humicola and Chlorella vulgaris: Implication on lipid synthesis, mineral nutrients and antioxidant system

•Algae C. humicola and C. vulgaris can tolerate NaCl to a concentration of 100 mM.•C. humicola exhibited high tolerance responses, biomass, lipid and proline content.•Increased cell size under NaCl treatment linked with high metabolites accumulation.•SEM-EDS spectra addresses altered essential minerals in algae under NaCl stress. In the present study, microalgae Chlorococcum humicola and Chlorella vulgaris were grown in different concentrations of NaCl (25–1000 mM) to elucidate its impact on morphology, lipid synthesis, minerals status and antioxidative responses. Scanning Electron microscopy showed distorted cell morphology and increased cell size by 33.52% (C. humicola) and 27.79% (C. vulgaris) at 100 mM NaCl. Energy Dispersive Spectroscopy data revealed reduction in mineral contents (C, S, Fe, Mg, Si, Mn and Zn) by 14–54% in both algae. Further, C. humicola was found to have high lipid content than C. vulgaris under NaCl regime. The activities of superoxide dismutase, catalase and glutathione reductase were increased by 2.5–5 folds in both algae as compared to control. The increased level of ascorbate, cysteine and proline in both algae indicated tolerance against salinity. Thus, C. humicola and C. vulgaris may exhibit dual benefits viz., high lipid production and reclamation of sodic soil.