The effect of heavy metals on the viability of Tetraselmis marina AC16-MESO and an evaluation of the potential use of this microalga in bioremediation

The use of microalgae in biotechnological processes has received much attention worldwide. This is primarily due to the fact that they are inexpensive to grow, requiring only sunlight and CO2, whilst lending themselves to a range of uses, such as to reduce CO2 levels, as fish feed, in biofuel production, for the generation of secondary metabolites of interest, and in bioremediation. These features mean that microalgae are excellent candidates for the implementation of a range of eco-friendly technologies. Here, we investigated the behavior and feasibility of the use of the microalgal strain Tetraselmis marina AC16-MESO against heavy metal contamination focused on potential use in bioremediation. The following key parameters were recorded: (i) the sedimentation efficiency, which reached 95.6% after five hours of decantation; (ii) the ion tolerance (Ca2+, Co2+, Cu2+, Fe3+, Mn2+ and Ni2+) at concentrations of 0.1, 1.0, 5.0, 10.0 and 20.0 mg*L-1 and (iii) ion removal efficiency (Cu2+, Fe3+ and Mn2+). Our results indicated a higher tolerance for iron and calcium (20 +/- 1.10 mg*L-1; 100 +/- 8.10 mg*L-1), partial to nickel, manganese and copper (4.4 +/- 0.10 mg*L-1; 4.4 +/- 0.15 mg*L-1; 5 +/- 1.25 mg*L-1) and less for cobalt (0.1 +/- 0.20 mg*L-1). Moreover, removal efficiency of 40-90% for Cu2+, 100% for Fe3+, and 20-50% for Mn2+ over a 72 hours period, for ion concentrations of 1.0 and 5.0 mg*L--(1).