Shifts in photosynthetic parameters and lipid production of the freshwater microalga Selenastrum gracile (Chlorophyceae) under cadmium exposure

• Published in: Journal of applied phycology 2020-12, Vol.32 (6), p.4047-4055
• Main Authors: Rocha, Giseli Swerts, Parrish, Christopher C., Espíndola, Evaldo L. G.
• Format: Article
• Language: English
• Subjects: Acetone; Algae; Algal growth; Aliphatic hydrocarbons; Anthropogenic factors; Biomedical and Life Sciences; Cadmium; Chlorophyceae; Chlorophyll; Chlorophyll a; Conformation; Damage; Ecology; Exposure; Fatty acids; Freshwater; Freshwater & Marine Ecology; Heavy metals; Inland water environment; Life Sciences; Lipids; Microalgae; Parameters; Phospholipids; Photosynthesis; Photosynthetic apparatus; Plant Physiology; Plant Sciences; Polyunsaturated fatty acids; Saturated hydrocarbons; Selenastrum gracile; Sterols; Trophic levels
• ISSN: 0921-8971; 1573-5176
• DOI: 10.1007/s10811-020-02255-5

The amount of metals released into the environment can increase with anthropogenic activities and different trophic levels can be affected. In the present study, we evaluated the changes in growth, chlorophyll content, photosynthetic parameters, and lipid and fatty acid (FA) contents of the freshwater microalga Selenastrum gracile (Chlorophyceae) exposed to sublethal concentrations of cadmium for 72 h. Our results show that Cd negatively affected algal growth and chlorophyll a increased per cell under Cd exposure. Photosynthetic parameters (maximum and operational yield, as well as quenching) were affected under Cd exposure, indicating damage to the photosynthetic apparatus. The amount of lipids and fatty acids increased with the increase of Cd in the medium. The most affected lipid classes under metal exposure were aliphatic hydrocarbon (HC), acetone mobile polar lipid (AMPL), and phospholipid (PL). Based on our results, we suggest that the production of algal lipids and fatty acids changed as a response to the amount of metal in the medium, avoiding photosynthetic damage at the lowest Cd concentration with the increase of polyunsaturated fatty acids (PUFA). However, at higher concentrations, the maintenance of the high values of PUFA was not observed and there was a decrease in the unsaturation of FA, resulting in higher amounts of MUFA. In addition, the percentage of structural lipids (sterol—ST—and PL) also decreased at the highest concentration. This, in combination with the decreased unsaturation of FA, suggests changes in membrane conformation and, consequently, damage to the photosynthetic machinery in the presence of Cd.