Shifts in photosynthetic parameters and lipid production of the freshwater microalga Selenastrum gracile (Chlorophyceae)
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Shifts in photosynthetic parameters and lipid production of the freshwater microalga Selenastrum gracile (Chlorophyceae) under cadmium exposure Giseli Swerts Rocha 1
&
Christopher C. Parrish 2
&
Evaldo L. G. Espíndola 1
Received: 22 April 2020 / Revised and accepted: 10 September 2020 # Springer Nature B.V. 2020
Abstract 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. Keywords Chlorophyta . Fatty acids . Lipid classes . Phyto-PAM . Photosynthetic apparatus
Introduction The essentiality of some metals, such as copper (Cu) as a micronutrient to algae is well known, e.g., acting in processes such as growth, respiration, and photosynthesis in freshwater (Bossuyt and Janssen 2005; Perales-Vela et al. 2006) and in
* Giseli Swerts Rocha [email protected] Christopher C. Parrish [email protected] Evaldo L. G. Espíndola [email protected] 1
NEEA/CRHEA, São Carlos School of Engineering, University of São Paulo (USP), Avenida Trabalhador Sãocarlense, 400, Parque Arnold Schmidt, São Carlos, SP CEP 13566-590, Brazil
2
Department of Ocean Sciences, Memorial University of Newfoundland, St. John’s, NL A1C 5S7, Canada
marine species (Peers and Price 2006). Cadmium (Cd) was shown to be essential for a marine diatom species (Lane et al. 2005) and can substitute for Zn in Zn-deficient marine diatoms (Price and Morel 1990; Lee et al. 1995); however, it has no more known functions in other species. The amount of Cd in the environment can increase w
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